Disinfection byproducts formed during drinking water treatment reveal an export control point for dissolved organic matter in a subalpine headwater stream

Changes in climate, season, and vegetation can alter organic export from watersheds. While an accepted tradeoff to protect public health, disinfection processes during drinking water treatment can adversely react with organic compounds to form disinfection byproducts (DBPs). By extension, DBP monitoring can yield insights into hydrobiogeochemical dynamics within watersheds and their implications for water resource management. In this study, we analyzed temporal trends from a water treatment facility that sources water from Coal Creek in Crested Butte, Colorado. These trends revealed a long-term increase in haloacetic acid and trihalomethane formation over the period of 2005-2020. Disproportionate export of dissolved organic carbon and formation of DBPs that exceeded maximum contaminant levels were consistently recorded in association with late spring freshet. Synoptic sampling of the creek in 2020 and 2021 identified a biogeochemical hotspot for organic carbon export in the upper domain of the watershed that contained a prominent fulvic acid-like fluorescent signature. DBP formation potential analyses from this domain yielded similar ratios of regulated DBP classes to those formed at the drinking water facility. Spectrometric qualitative analyses of pre and post-reacted waters with hypochlorite indicated lignin-like and condensed hydrocarbon-like molecules were the major reactive chemical classes during chlorine-based disinfection. This study demonstrates how drinking water quality archives combined with synoptic sampling and targeted analyses can be used to identify and understand export control points for dissolved organic matter. This approach could be applied to identify and characterize analogous watersheds where seasonal or climate-associated organic matter export challenge water treatment disinfection and by extension inform watershed management and drinking water treatment.

Characterizing the exposure of streams in southern Ontario to agricultural pesticides

Aquatic communities can be exposed to pesticides transported from land. Characterizing this exposure is key to predicting potential toxic effects. In this study, samples of streamwater from 21 sites were used to characterize pesticide exposure to aquatic communities. Sites were in agricultural areas of southwestern Ontario, Canada and were sampled monthly from 2012 to 2019 from April to November. Samples were analyzed for a suite of hundreds of pesticides and pesticide degradation products and other water quality indicators (e.g., nutrients). Frequently detected pesticides included herbicides (2,4-D; bentazon; MCPP; metolachlor) and neonicotinoid insecticides (NNIs) (clothianidin; thiamethoxam) which were detected in >50% of samples collected between 2015 and 2019. Non-metric multidimensional scaling (NMDS) was used to explore connections between pesticide concentrations and upstream land use and crop type. Detectable concentrations of the NNI clothianidin and many herbicides were related to corn, soybean, and grain/cereal crops while concentrations of the NNI imidacloprid, insecticide flonicamid, and fungicide boscalid were related to greenhouse/nursery land use. Potential toxicity to aquatic communities was assessed by comparing pesticide concentrations to Pesticide Toxicity Index (PTI) values. Few samples exceeded levels where acute (1% of samples) or chronic toxicity (10.5%) would be expected. The diamide insecticide chlorantraniliprole was detected in several streamwater samples at levels that may cause toxicity to aquatic invertebrates, highlighting the need for continued toxicity research into this pesticide class. The number of pesticides detected was positively correlated with nutrient and total suspended solids levels, underscoring the multiple stressors aquatic communities are exposed to in these habitats.

Characterizing the impacts of macrophyte-dominated ponds on nitrogen sources and sinks by coupling multiscale models

Macrophyte-dominated ponds, widely distributed in lowland areas, play an important role in nitrogen (N) retention for nonpoint source pollution. However, their impacts on N sources and sinks are scarcely quantified at a watershed scale. This study aimed to investigate N dynamics (sources, sinks, transport, etc.) of macrophyte-dominated ponds and their driving factors in a typical lowland artificial watershed (the Zhong River Watershed) in East China. For this purpose, an hourly-scale pond model (nitrogen dynamic model for macrophyte-dominated ponds, NDP-Pond) was developed, and coupled with a daily scale watershed model (Nitrogen Dynamic Polder model, NDP) to simulate N dynamics, and estimate N retention in macrophyte-dominated ponds. A comparison with the measured water level and total nitrogen (TN) revealed an acceptable model performance (coefficient of determination (R²) > 0.53) for these two models. Based on the N source/sink simulations, we found that 1) macrophyte-dominated ponds showed a large TN removal capacity with a rate of 55%, and a TN loading removal rate of 67 kg·ha^-1·yr^-1. 2) Denitrification was the main pathway for N removal with a contribution of 57.7%, followed by the uptake of macrophytes (35.8%) and sedimentation (6.5%). 3) The optimal coverage of macrophytes (Alternanthera philoxeroides) to enhance N removal is 2-4 kg·m^-2. 4) During the macrophyte-growth period, the TN removal capacity of the pond was higher with a retention time of 1-10 days. Increasing the pond retention time would decrease the N removal efficiency. This study revealed the high value of coupling multiscale models to gain in-depth insights into N retention in macrophyte-dominated pond ecosystems.

Effects of land use, climate, and imperviousness on urban stormwater quality: A meta-analysis

Many natural and anthropogenic factors cause degradation of urban stormwater quality, resulting in negative consequences to receiving waters. In order to improve water quality models at a variety of scales, accurate estimates of pollutant (nutrients, total suspended solids, and heavy metal) concentrations are needed using potential explanatory variables. To this end, a meta-analysis was performed on aggregated stormwater quality data from the published literature from 360 urban catchments worldwide to understand how urban land use and land cover (LULC), climate (i.e., Kӧppen-Geiger zone), and imperviousness (1) affect runoff quality, and (2) whether they are able to predict stormwater pollutant concentrations. Runoff pollutant concentrations were more influenced by LULC and climate than imperviousness. Differences in LULC significantly affected the generation of metals and some nitrogen species. Road, city center, and commercial LULCs generally produced the most elevated pollutant concentrations. Changes in climate zones resulted in significant differences in concentrations of nutrients and metals. Continental and arid climate zones produced runoff with the highest pollutant concentrations. Rainfall patterns seemed to have a more important role in affecting runoff quality than seasonal temperature. Differences in imperviousness only significantly affected chromium and nickel concentrations, although increased imperviousness led to slightly (not significantly) elevated concentrations of nutrients, suspended solids, and other heavy metals. Multiple linear regression models were created to predict the quality of urban runoff. Predictive equations were significant (p < 0.05) for 67% of the pollutants analyzed (ammonia, total Kjeldahl nitrogen, total nitrogen, total phosphorus, cadmium, nickel, lead, and zinc) suggesting that LULC, climate, and imperviousness are useful predictors of stormwater quality when local field monitoring or modeling is not practical. This study provides useful relationships to better inform urban stormwater quality models and regulations such as total maximum daily loads.

The time of concentration application in studies around the world: a review

The time of concentration (Tc) is the main hydrological parameter used to characterize the response of a given Hydrological Response Unit (HRU) to a precipitation event. Because of its importance, the determining Tc is an integral step in several studies involving runoff. Thus, this work presents an unprecedented review of the application of Tc in different lines of research involving water resources around the world. In this article, 1252 publications were listed, obtained from seven different databases, published by 2020, that presented the expressions "time of concentration," "runoff," and "watershed." The articles and conference papers obtained in this research were classified into 12 topics. The number of publications per topic and per country was measured and a cluster analysis was developed to verify the similarity of the distribution of topics per country. In addition, 125 equations applied in related publications for the estimation of Tc are also listed. Graphical abstract.

Cost/benefit assessment of green infrastructure: Spatial scale effects on uncertainty and sensitivity

Green infrastructure (GI) is becoming a common solution to mitigate stormwater-related problems. Given the uncertain costs of GI relative to other stormwater management strategies, stakeholders investing in GI need performance-analysis tools that consider the full suite of benefits and the impacts of uncertainty to help justify GI expenditures. This study provides a quantitative and comparative analysis of GI benefits, including nutrient uptake from stormwater and air pollutant deposition. Economic costs and benefits of GI are assessed using two metrics, benefit-cost ratios (BCRs) and nutrient removal costs, at three scales: household, subwatershed, and watershed scale. Results from a case study in the state of Maryland show that the costs of nutrient uptake at the subwatershed scale can be lower than those at either the watershed or household scales. Moreover, rain gardens are far more efficient in stormwater treatment at the household scale in comparison to watershed scale, for which large-scale dry or wet basins are more efficient. Using a BCR metric, smaller subwatersheds show more promise, while using a nutrient removal cost metric indicates that upstream subwatersheds are more suitable for stormwater treatment. The results also show that implementation of GI at all potential pervious locations does not necessarily increase nutrient removal costs and that self-installation of rain gardens greatly reduces nutrient removal costs. Finally, the results show that using numerous small-sized rain garden practices in front of residential buildings yields lower nutrient removal costs in comparison to permeable pavements placed in parking lots and commercial buildings.

Study on the spatial changes concerning ecosystem services value in Lhasa River Basin, China

In this study, the outcome serves to establish a measurement model to calculate the value of ecosystem services in Lhasa River Basin, China. Following on the principle of resource scarcity, a study paradigm is established according to the influence of natural and socio-economic location differences on the value of ecosystem services. Results show that the total value of ecosystem services in Lhasa River Basin is 104.503 billion yuan. The unit ecosystem service value of natural grassland in the lower reaches is 5.6 times and 1.07 times larger than that in the upper and middle reaches, respectively. The value of ecosystem services is clearly affected by the scarcity of ecosystem services and dependence of economic and social development on the ecosystem. The value of ecosystem services in the upper, middle, and lower reaches were 4.17%, 21.48%, and 74.35%, respectively. It is found that the value of ecosystem services in this particular region differs significantly in the upper, middle, and lower reaches of the basin. The scarcity of ecological resources has increased the value of ecosystem services, which is reflected in the highest value of ecosystem services in the middle of Lhasa River Valley and both sides of the river where population, economy, and ecological demand are relatively concentrated. According to the estimated results, this study proposes a variety of methods to improve the ecosystem service value and analysis of the ecological compensation mechanism, derived from the contribution made by ecological services.

Improving the design and implementation of sediment fingerprinting studies: summary and outcomes of the TRACING 2021 Scientific School

PURPOSE

Identifying best practices for sediment fingerprinting or tracing is important to allow the quantification of sediment contributions from catchment sources. Although sediment fingerprinting has been applied with reasonable success, the deployment of this method remains associated with many issues and limitations.

METHODS

Seminars and debates were organised during a 4-day Thematic School in October 2021 to come up with concrete suggestions to improve the design and implementation of tracing methods.

RESULTS

First, we suggest a better use of geomorphological information to improve study design. Researchers are invited to scrutinise all the knowledge available on the catchment of interest, and to obtain multiple lines of evidence regarding sediment source contributions. Second, we think that scientific knowledge could be improved with local knowledge and we propose a scale of participation describing different levels of involvement of locals in research. Third, we recommend the use of state-of-the-art sediment tracing protocols to conduct sampling, deal with particle size, and examine data before modelling and accounting for the hydro-meteorological context under investigation. Fourth, we promote best practices in modelling, including the importance of running multiple models, selecting appropriate tracers, and reporting on model errors and uncertainty. Fifth, we suggest best practices to share tracing data and samples, which will increase the visibility of the fingerprinting technique in geoscience. Sixth, we suggest that a better formulation of hypotheses could improve our knowledge about erosion and sediment transport processes in a more unified way.

CONCLUSION

With the suggested improvements, sediment fingerprinting, which is interdisciplinary in nature, could play a major role to meet the current and future challenges associated with global change.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11368-022-03203-1.

Improving streamflow simulation by combining hydrological process-driven and artificial intelligence-based models

Accurate and timely monitoring of streamflow and its variation is crucial for water resources management in watersheds. This study aimed at evaluating the performance of two process-driven conceptual rainfall-runoff models (HBV: Hydrologiska Byråns Vattenbalansavdelning, and NRECA: Non Recorded Catchment Areas) and seven hybrid models based on three artificial intelligence (AI) methods (adaptive neuro-fuzzy inference system (ANFIS), support vector machine (SVM), and group method of data handling (GMDH)) in simulating streamflow in four river basins in Indonesia. HBV and NRECA were developed based on precipitation data. Various combinations of 1-month lagged precipitation data together with outputs of HBV and NRECA were used for developing ANFIS and SVM models, and the best results of ANFIS and SVM formed the inputs to GMDH. Results showed that AI-based hybrid models have generally led to more accurate streamflow estimates compared with HBV and NRECA, and the GMDH model had the best performance at Cipero, Kedungdowo, Notog, and Sukowati stations, with RMSEs of 12.21, 6.07, 20.35, and 24.2 m³ s^-1, respectively. More accurate estimation of peak values in training set at Cipero and Sukowati stations, and in both training and testing sets at Kedungdowo station was another advantage of GMDH. Hybrid models based on AI methods can be suitable alternatives to hydrological models, particularly in watersheds where there is a lack of measured data (e.g. climatic parameters, land cover-plant growth data, soil data, stream conditions, and properties of groundwater aquifers), provided that appropriate inputs are used.

Assessment of heavy metal pollution and ecological risk in river water and sediments in a historically metal mined watershed, Northeast Japan

Mining legacies continue to impact the geochemical cycles in historically mined watersheds after mine closure. The Hokuroku District in Northeast Japan is a famous metal mining area with a long mining history; however, studies on the distribution mechanisms and pollution characteristics of heavy metals in these historically mined watersheds after the boom period of mining activities are lacking. This study aims to provide fundamental insights into the effects of the mining activities and hydrological conditions on heavy metal pollution in the Kosaka watershed, Hokuroku District. Sampling was performed in terms of watershed segmentation, and the outlet of the tributary within each sub-watershed was also sampled to capture the diffusional pollution status. The distributions of Zn, Cu, Cd, Pb and As in river water and sediments, as well as their pollution characteristics and ecological risks, were analysed under different hydrological conditions. Our findings provide evidence of the ecological risk in surface water induced by Zn, Cu and Pb pollution in the Kosaka River system. In a high proportion of the sub-watershed, there was moderate to strong enrichment in Cd, Cu and Zn in the river sediments. The sub-watersheds with high pollution levels and ecological risk were highly consistent with the sub-watersheds encompassing abandoned mine sites. Suspended particles carried large amounts of Pb and Cu, especially on rainy days. The heavy metal contents in river water were very sensitive to occasional rainfall events; rainy days posed the most risk to organisms in the Kosaka River, followed by the low-water-level season and the high-water-level season.

Evaluating the impact of watershed development and climate change on stream ecosystems: A Bayesian network modeling approach

A continuous-variable Bayesian network (cBN) model is used to link watershed development and climate change to stream ecosystem indicators. A graphical model, reflecting our understanding of the connections between climate change, weather condition, loss of natural land cover, stream flow characteristics, and stream ecosystem indicators is used as the basis for selecting flow metrics for predicting macroinvertebrate-based indicators. Selected flow metrics were then linked to variables representing watershed development and climate change. We fit the model to data from two river basins in southeast US and the resulting model was used to simulate future stream ecological conditions using projected future climate and development scenarios. The three climate models predicted varying ecological condition trajectories, but similar worst-case ecological conditions. The established modeling approach couples mechanistic understanding with field data to develop predictions of management-relevant variables across a heterogeneous landscape. We discussed the transferability of the modeling approach.

Profiling of Microbial Communities in the Sediments of Jinsha River Watershed Exposed to Different Levels of Impacts by the Vanadium Industry, Panzhihua, China

The mining, smelting, manufacturing, and disposal of vanadium (V) and associated products have caused serious environmental problems. Although the microbial ecology in V-contaminated soils has been intensively studied, the impacted watershed ecosystems have not been systematically investigated. In this study, geochemistry and microbial structure were analyzed along ~30 km of the Jinsha River and its two tributaries across the industrial areas in Panzhihua, one of the primary V mining and production cities in China. Geochemical analyses showed different levels of contamination by metals and metalloids in the sediments, with high degrees of contamination observed in one of the tributaries close to the industrial park. Analyses of the V4 hypervariable region of 16S rRNA genes of the microbial communities in the sediments showed significant decrease in microbial diversity and microbial structure in response to the environmental gradient (e.g., heavy metals, total sulfur, and total nitrogen). Strong association of the taxa (e.g., Thauera, Algoriphagus, Denitromonas, and Fontibacter species) with the metals suggested selection for these potential metal-resistant and/or metabolizing populations. Further co-occurrence network analysis showed that many identified potential metal-mediating species were among the keystone taxa that were closely associated in the same module, suggesting their strong inter-species interactions but relative independence from other microorganisms in the hydrodynamic ecosystems. This study provided new insight into the microbe-environment interactions in watershed ecosystems differently impacted by the V industries. Some of the phylotypes identified in the highly contaminated samples exhibited potential for bioremediation of toxic metals (e.g., V and Cr).

Multivariate analysis of factors influencing the peak flow and runoff volume in the Cerrado and Atlantic Forest biomes in Brazil

This study evaluates the influence of physiographic characteristics on the peak flow to runoff volume ratio in watersheds belonging to the Cerrado and Atlantic Forest biomes, in the Center-South region of Brazil. Specifically, the peak flow and runoff volume values obtained in the outlet section are related to the physiographic characteristics of the watersheds. Using a geographic information system tool, 13 watersheds are delimited, and 38 variables are selected from each watershed. A recursive digital filter is used to separate the direct (surface) flow from base (groundwater) flow. Data are analyzed using multivariate statistics, which allows interpretation of the structure of a data set from the respective correlation matrices. The results indicate that the peak flow and runoff volume are strongly correlated with the physical characteristics of the watersheds and the types of anthropogenic activity in both biomes. Furthermore, the presence of woods and forests reduces the peak flow and runoff volume.

Watershed modelling development for generating runoff estimation of Sarida Catchment/Central West Bank

Watershed modelling was carried out in Sarida Catchment in the West Bank (Palestine) in order to determine the physical characteristics of the watershed. Generated storm water and runoff were estimated for watershed sub-catchments for enhancing the potentiality of rainwater harvesting development. Climatic data across eight years (seven wet seasons) were used for watershed modelling by using the software application systems of Watershed Modelling and Hydrologic Modelling. The Geographical Information System (GIS) and Microsoft Excel were used as well for the estimation of different model parameters and features. The physical and meteorological characteristics for each sub-catchment including land use, topography, soil, rainfall, and other parameters were identified. The model results provided sensitive conceptual principles for understanding the runoff mechanisms in the watershed. The average generated storm water over the seven seasons (2008/09 to 2014/15) is 23.16 and 13.44 Mm³/year for northern and southern sub-catchments in Sarida watershed, respectively. The generated runoff of the sub-catchments over this period ranged between 2.13 and 23.18 million cubic meters per year. The results suggest a high potential for rainwater harvesting to promote agricultural development and the need to establish a climatic monitoring network in Sarida watershed, as well as in other catchments in the West Bank, for better informing watershed management practices and policies.

Science and scale mismatch: Horizontal and vertical information sharing in the Puget Sound polycentric governance system

Environmental governance in complex social-ecological systems involves multiple actors and institutions that interact across scales. Where hierarchical authority to command is lacking, actors may rely on resource sharing to steer actions across the landscape and reduce scale mismatch. An important resource for such cross-scale steering is scientific information. This study examines how actors in local collaborative organizations share and use scientific information across multiple parts of a polycentric governance system. Interviews from efforts in the Puget Sound, USA, to incorporate scientific information across scales reveal patterns in horizontal and vertical information sharing, the role of knowledge brokers, and scale mismatches in spatial scale and theory vs applied research. Results indicate collaborative group members frequently access scientific findings horizontally through their networks of contacts and conference attendance, as well as through document searches for journal articles and government reports. Vertical transmission relies more on knowledge brokers and guidance documents. The use of scientific findings by local collaborative organizations depends on the biophysical and political context, and there is often tension between scientific rigor and local applicability.

Lesion segmentation in breast ultrasound images using the optimized marked watershed method

BACKGROUND

Breast cancer is one of the most serious diseases threatening women's health. Early screening based on ultrasound can help to detect and treat tumours in the early stage. However, due to the lack of radiologists with professional skills, ultrasound-based breast cancer screening has not been widely used in rural areas. Computer-aided diagnosis (CAD) technology can effectively alleviate this problem. Since breast ultrasound (BUS) images have low resolution and speckle noise, lesion segmentation, which is an important step in CAD systems, is challenging.

RESULTS

Two datasets were used for evaluation. Dataset A comprises 500 BUS images from local hospitals, while dataset B comprises 205 open-source BUS images. The experimental results show that the proposed method outperformed its related classic segmentation methods and the state-of-the-art deep learning model RDAU-NET. Its accuracy (Acc), Dice similarity coefficient (DSC) and Jaccard index (JI) reached 96.25%, 78.4% and 65.34% on dataset A, and its Acc, DSC and sensitivity reached 97.96%, 86.25% and 88.79% on dataset B, respectively.

CONCLUSIONS

We proposed an adaptive morphological snake based on marked watershed (AMSMW) algorithm for BUS image segmentation. It was proven to be robust, efficient and effective. In addition, it was found to be more sensitive to malignant lesions than benign lesions.

METHODS

The proposed method consists of two steps. In the first step, contrast limited adaptive histogram equalization (CLAHE) and a side window filter (SWF) are used to preprocess BUS images. Lesion contours can be effectively highlighted, and the influence of noise can be eliminated to a great extent. In the second step, we propose adaptive morphological snake (AMS). It can adjust the working parameters adaptively according to the size of the lesion. Its segmentation results are combined with those of the morphological method. Then, we determine the marked area and obtain candidate contours with a marked watershed (MW). Finally, the best lesion contour is chosen by the maximum average radial derivative (ARD).

Climate and atmospheric deposition drive the inter-annual variability and long-term trend of dissolved organic carbon flux in the conterminous United States

The lateral flux of dissolved organic carbon (DOC) from soils to inland waters and ultimately to the ocean represents a fundamental component of the global carbon cycle. To estimate the DOC flux, we developed an empirical terrestrial-aquatic DOC fluxes model (TAF-DOC). TAF-DOC incorporates various environmental factors (e.g., meteorology, sulfur, and nitrogen deposition) that to-date have not been comprehensively considered or well-represented in existing modeling frameworks. TAF-DOC was applied to estimate spatial-temporal patterns of DOC flux and potential fates across the conterminous United States during the 1985 to 2018 time period. Our results suggest that TAF-DOC successfully characterized spatial-temporal of DOC flux. As expected, the interannual pattern of DOC flux was strongly regulated by precipitation, but the long-term trend was significantly influenced by the rate of atmospheric wet sulfur deposition. From 1985 to 2018, TAF-DOC estimated DOC loading from terrestrial to aquatic ecosystems in the conterminous United States to be 33.5 ± 2.2 TgC per year, which was roughly 0.39-0.49% of total soil organic carbon stock estimates. The dominant fate of terrestrially-derived DOC was delivery to the coastal ocean in riverine export (41%), with another 21% buried in sediment and the remaining 12.8 ± 0.4 TgC per year (38%) returned to the atmosphere through outgassing from inland waters. Assuming the quantities of DOC sediment burial and export to the ocean as an annual sink of terrestrially-derived carbon, budget inventories and models that do not account for DOC flux in the conterminous United States will underestimate the net annual carbon sink by as much as 5.5-6.4%.

Meanders as a scaling motif for understanding of floodplain soil microbiome and biogeochemical potential at the watershed scale

BACKGROUND

Biogeochemical exports from watersheds are modulated by the activity of microorganisms that function over micron scales. Here, we tested the hypothesis that meander-bound regions share a core microbiome and exhibit patterns of metabolic potential that broadly predict biogeochemical processes in floodplain soils along a river corridor.

RESULTS

We intensively sampled the microbiomes of floodplain soils located in the upper, middle, and lower reaches of the East River, Colorado. Despite the very high microbial diversity and complexity of the soils, we reconstructed 248 quality draft genomes representative of subspecies. Approximately one third of these bacterial subspecies was detected across all three locations at similar abundance levels, and ~ 15% of species were detected in two consecutive years. Within the meander-bound floodplains, we did not detect systematic patterns of gene abundance based on sampling position relative to the river. However, across meanders, we identified a core floodplain microbiome that is enriched in capacities for aerobic respiration, aerobic CO oxidation, and thiosulfate oxidation with the formation of elemental sulfur. Given this, we conducted a transcriptomic analysis of the middle floodplain. In contrast to predictions made based on the prominence of gene inventories, the most highly transcribed genes were relatively rare amoCAB and nxrAB (for nitrification) genes, followed by genes involved in methanol and formate oxidation, and nitrogen and CO₂ fixation. Within all three meanders, low soil organic carbon correlated with high activity of genes involved in methanol, formate, sulfide, hydrogen, and ammonia oxidation, nitrite oxidoreduction, and nitrate and nitrite reduction. Overall, the results emphasize the importance of sulfur, one-carbon and nitrogen compound metabolism in soils of the riparian corridor.

CONCLUSIONS

The disparity between the scale of a microbial cell and the scale of a watershed currently limits the development of genomically informed predictive models describing watershed biogeochemical function. Meander-bound floodplains appear to serve as scaling motifs that predict aggregate capacities for biogeochemical transformations, providing a foundation for incorporating riparian soil microbiomes in watershed models. Widely represented genetic capacities did not predict in situ activity at one time point, but rather they define a reservoir of biogeochemical potential available as conditions change. Video abstract.

Assessing the hydrogeological resilience of a groundwater-dependent Mediterranean peatland: Impact of global change and role of water management strategies

Mediterranean peatlands remain largely under-documented, except for detailed biological data such as fauna and flora taxa lists, and yet are increasingly threatened by water withdrawal and agriculture practices. This lack of information, particularly on their hydrogeological functioning, makes it impossible to evaluate their response to changing climate conditions. A pilot study on a representative Mediterranean peatland on the island of Corsica (France) was conducted to evaluate recharge modalities in the peatland using a coupled water-level monitoring, geochemical and isotope multi-tracing approach (electric conductivity, major ions, δ¹⁸O, δ²H, ³H, ⁸⁷Sr/⁸⁶Sr). The goal was to understand how water budgets in peatland ecosystems were maintained throughout the year, especially during the summer. Despite the remarkable stability of the peatland water level, the recharge contributions of varied water bodies through an alluvial aquifer vary significantly from one season to another. An end-member mixing analysis (EMMA) indicates that the peatland is mainly recharged by an alluvial aquifer. During fall-winter, the alluvial aquifer on which the peatland depends is recharged by the rainfall, a river, and shallow groundwater (colluvium). During spring-summer, water supply is provided mostly by a river, shallow, and deep groundwater (fractured granite). However, this specific hydrogeological functioning is not taken into account by environmental management policies making peatlands vulnerable to anthropogenic and climatic pressures. Thus, their actual status regarding water and aquatic environment management policies is discussed to provide recommendations for better consideration and preservation.

Reliability theory for microbial water quality and sustainability assessment

Microbial surface water contamination can disrupt critical ecosystem services such as recreation and drinking water supply. Prediction of water contamination and assessment of sustainability of water resources in the context of water quality are needed but are difficult to achieve - with challenges arising from the complexity of environmental systems, and stochastic variability of processes that drive contaminant fate and transport. In this paper we use reliability theory as a framework to address these issues. We define failure as exceedance of regulatory water contamination limits, and system components as reaches in the surface water network. We then methodically study the reliability of each component in the context of water quality, as well as the impact of individual components on overall water quality and sustainability. We obtain spatially distributed probability- and physics-based sustainability measures of reliability, vulnerability, resilience and the sustainability index. Finally, we use GIS as a platform to present these measures as geospatial products in an effort to foster public acceptance of probability-based methods in contaminant hydrology.

Shifts in precipitation and agricultural intensity increase phosphorus concentrations and loads in an agricultural watershed

Fertilizers and manure applied to cropland to increase yields are often lost via surface erosion, soil leaching, and runoff, increasing nutrient loads in surface and sub-surface waters, degrading water quality, and worsening the 'dead zone' in the Gulf of Mexico. We leverage spatial and temporal variation in agricultural practices and precipitation events to examine how these factors affect stream total phosphorus (TP) concentrations and loads in the Sugar River (Wisconsin), recently listed as impaired. To perform our analysis, we first collected water quality data from 1995 to 2017 from 40 sites along the Sugar River and its tributaries. Starting in 2004, three dairy farms expanded to become concentrated animal feeding operations (CAFOs) in this watershed. We then estimated how time of year, stream position, discharge volume, and proximity to the newly expanded CAFOs affected TP concentrations and loads. Total P concentrations, which ranged from 0.02 to 1.4 mg/L and often exceeded the EPA surface water standard of 0.1 mg/L, increased with increases in stream discharge and proximity to dairy operations, peaking in early spring to mid-summer coincident with extreme precipitation events. Our empirical analysis also shows that TP concentrations downstream from the newly permitted CAFOs increased by 19% relative to upstream concentrations. When examining total daily phosphorus loads (concentration × discharge) from this 780 km² watershed, we found that loads ranged from 5.88 to 4801 kg. Compared to upstream TP loads, those downstream from the CAFOs increased by 91% after the expansions - over four times that of concentration increases - implying that the rate of downstream phosphorus transfer has increased due to CAFO expansion. Our results argue for standards that focus on loads rather than concentrations and monitoring that includes peak events. As agriculture intensifies and extreme rainfall events become more frequent, it becomes increasingly important to limit soil and TP runoff from manure and fertilizer. Siting CAFOs carefully, limiting their size, and improving farming practices in proximity to CAFOs in spring and early summer could considerably reduce nutrient loads.

Impacts and social implications of landuse-environment conflicts in a typical Mediterranean watershed

In coastal watersheds, services and landuse favour coastal tourism and urbanization, depriving rural upstream of infrastructure and attention. This unbalanced management leads to an intensification of socioeconomic changes that generate a structural heterogeneity of the landscape and a reduction in the livelihoods of the rural population. The incessant dissociation between the objectives of the stakeholders triggers landuse-environment-economy conflicts which threaten to mutate large-scale development programs. Here, we used multi-assessment techniques in a Mediterranean watershed from Morocco to evaluate the effects of landuse change on water, vegetation, and perception of the rural population towards environmental issues. We combined complementary vegetation indexes (NDVI and EVI) to study long-term landuse change and phenological statistical pixel-based trends. We assessed the exposure of rural households to the risk of groundwater pollution through a water analysis supplemented by the calculation of an Integrated Water Quality Index. Later, we contrasted the findings with the results of a social survey with a representative sample of 401 households from 7 villages. We found that rapid coastal linear urbanization has resulted in a 12-fold increase in construction over the past 35 years, to the detriment of natural spaces and the lack of equipment and means in rural areas upstream. We show that the worst water qualities are linked to the negative impact of anthropogenic activities on immediately accessible water points. We observe that rural households are aware of the existence and gravity of environmental issues but act confusedly because of their low education level which generates a weak capacity to understand cause and effect relationships. We anticipate the pressing need to improve the well-being and education of the population and synergistically correct management plans to target the watershed as a consolidated system. Broadly, stakeholders should restore lost territorial harmony and reallocate landuse according to a sustainable environment-socioeconomic vision.

Sarcocystis neurona Transmission from Opossums to Marine Mammals in the Pacific Northwest

Increasing reports of marine mammal deaths have been attributed to the parasite Sarcocystis neurona. Infected opossums, the only known definitive hosts, shed S. neurona sporocysts in their feces. Sporocysts can contaminate the marine environment via overland runoff, and subsequent ingestion by marine mammals can lead to fatal encephalitis. Our aim was to determine the prevalence of S. neurona in opossums from coastal areas of Washington State (USA) and to compare genetic markers between S. neurona in opossums and marine mammals. Thirty-two road-kill opossums and tissue samples from 30 stranded marine mammals meeting inclusion criteria were included in analyses. Three opossums (9.4%) and twelve marine mammals (40%) were confirmed positive for S. neurona via DNA amplification at the ITS1 locus. Genetic identity at microsatellites (sn3, sn7, sn9) and the snSAG3 gene of S. neurona was demonstrated among one harbor porpoise and two opossums. Watershed mapping further demonstrated plausible sporocyst transport pathways from one of these opossums to the location where an infected harbor porpoise carcass was recovered. Our results provide the first reported link between S. neurona genotypes on land and sea in the Pacific Northwest, and further demonstrate how terrestrial pathogen pollution can impact the health of marine wildlife.

Optical properties and 14C ages of stream DOM from agricultural and forest watersheds during storms

Forest and agricultural land use affects the concentration and composition of dissolved organic carbon (DOC) in streams and rivers. To elucidate the impacts of forest and agricultural land use on stream DOC during storm events, we investigated DOC concentration ([DOC]), optical properties of dissolved organic matter (DOM), and Δ¹⁴C-DOC in both forest- and agriculture-dominated headwater streams in South Korea in the summer of 2012. One forested and five agricultural streams were investigated. During storms, the peak [DOC] of forest stream increased to 5.8 mg L^-1, approximately two times larger than that of the most agricultural stream (3.2 mg L^-1), demonstrating the weaker storm responses of the [DOC] of agricultural streams to hydrological change. Five PARAFAC components were identified, including three terrestrial humic-like substances (C1, C2, C3), one microbial humic substance (C4), and one microbial protein-like substances (C5). The mean (C4+C5)/(C1+C2+C3) of all storm events at the most agricultural stream was 1.5 times larger than that of the most forested stream, suggesting that more protein-like DOM is exported from agricultural watersheds. Whereas a forest stream was primarily composed of terrestrially derived and ¹⁴C-enriched modern DOC, the ¹⁴C-age of the most agricultural stream was up to ∼1000 years old. The results suggest that agricultural practices could decrease the old organic carbon pools from soils. However, how quickly the aged DOC can be degraded to CO₂ in streams is unknown, warranting future investigation on lability of the aged DOC and their effects on CO₂ evasion from rivers and estuaries downstream.

Urban rivers are hotspots of riverine greenhouse gas (N2O, CH4, CO2) emissions in the mixed-landscape chaohu lake basin

Growing evidence shows that riverine networks surrounding urban landscapes may be hotspots of riverine greenhouse gas (GHG) emissions. This study strengthens the evidence by investigating the spatial variability of diffusive GHG (N₂O, CH₄, CO₂) emissions from river reaches that drain from different types of landscapes (i.e., urban, agricultural, mixed, and forest landscapes), in the Chaohu Lake basin of eastern China. Our results showed that almost all the rivers were oversaturated with dissolved GHGs. Urban rivers were identified as emission hotspots, with mean fluxes of 470 μmol m^-2d^-1 for N₂O, 7 mmol m^-2d^-1 for CH₄, and 900 mmol m^-2d^-1 for CO₂, corresponding to ~14, seven, and two times of those from the non-urban rivers in the Chaohu Lake basin, respectively. Factors related to the high N₂O and CH₄ emissions in urban rivers included large nutrient supply and hypoxic environments. The factors affecting CO₂ were similar in all the rivers, which were temperature-dependent with suitable environments that allowed rapid decomposition of organic matter. Overall, this study highlights that better recognition of the influence that river networks have on global warming is required-particularly when it comes to urban rivers, as urban land cover and populations will continue to expand in the future. Management measures should incorporate regional hotspots to more efficiently mitigate GHG emissions.

Dataset of 18O and 2H in streamflow across Canada: A national resource for tracing water sources, water balance and predictive modelling

Oxygen-18 and deuterium were measured in streamflow samples collected from 331 gauging stations across Canada during 2013 to 2019. This dataset includes 9206 isotopic analyses made on 4603 individual water samples, and an additional 1259 analysis repeats for quality assurance/quality control. We also include arithmetic and flow-weighted averages, and other basic statistics for stations where adequate data were available. Station data are provided including station code, name, province, latitude, longitude and drainage area. Flow data were extracted from the historical database of the Water Survey of Canada. Details on the preliminary application of these data are provided in "18O and 2H in streamflow across Canada" [1]. Overall, these data are expected to be useful when combined with precipitation datasets and analytical or numerical models for water resource management and planning, including tracing streamflow source, water balance, evapotranspiration partitioning, residence time analysis, and early detection of climate and land use changes in Canada.

Spatiotemporal variations in chromophoric dissolved organic matter (CDOM) in a mixed land-use river: Implications for surface water restoration

A challenge for current surface water restoration and management in China is acquiring the source information for complex pollution scenarios in order to develop effective control strategies. As an important part of dissolved organic matter, chromophoric dissolved organic matter (CDOM) contains unique chemical signals related to various pollution sources. Spectral methods such as fluorescence excitation-emission matrices coupled with parallel factor analysis enable rapid and low-cost CDOM characterization for source tracking. In this study, a typical small-sized river flowing through mixed land-use regions in southeastern China, the Lujiang River, was investigated to determine the responses of CDOM to spatiotemporal factors. The effects of land-use patterns were reflected by the fluorescent components of terrestrial and sewage substances. A high and stable proportion of terrestrial-like components (C1 + C2) in each sampling period (i.e., March: 47.6 ± 5.7% and October: 44.3 ± 2.7%) indicated a high input of non-point source (NPS) pollution from both agriculture and urban areas. In addition, the difference in solar radiation intensity induced by climate and air quality changes was also reflected by variability in the photodegradation product component (C3) of terrestrial precursors between October (24.8 ± 2.6%) and March (4.5 ± 2.0%), suggesting that terrestrial components could be a sensitive indicator for NPS pollutant monitoring. Increased sewage impact in downstream regions was reflected by a spike in the tryptophan-like component (C4); temporal variations in C4 (paired t-Test, p < 0.005) also indicated that sewage substances were more prone to removal by microbial activity in warmer seasons. The dynamics of C4 could serve as a good indicator of sewage disposal performance. The results of this study demonstrate that CDOM data have important practical applications for existing water restoration campaigns in southeastern China, as well as substantial potential for routine water quality monitoring.

Microbiological assessment of an urban lagoon system in the coastal zone of Rio de Janeiro, Brazil

This study aims to assess microbiological contamination using a molecular tool for detection of multiple enteropathogens in a coastal ecosystem area in Rio de Janeiro, Brazil. Ten litres of superficial water samples were obtained during the spring ebb tide from sampling sites along the Jacarepaguá watershed. Samples were concentrated using skimmed milk flocculation method for TaqMan array card (TAC), designed to identify 35 enteric pathogens simultaneously, and single TaqMan qPCR analysis for detecting human adenovirus (HAdV) and JC human polyomavirus (JCPyV) as faecal indicator viruses (FIV). TAC results identified 17 enteric pathogens including 4/5 viral species investigated, 8/15 bacteria, 4/6 protozoa and 1/7 helminths. Escherichia coli concentration was also measured as faecal indicator bacteria (FIB) using Colilert Quanti-Tray System with positivity in all samples studied. HAdV and JCPyV qPCR were detected in 8 and 4 samples, respectively, with concentration ranging from 8 × 10² to 2 × 10⁶ genome copies/L. Partial nucleotide sequencing demonstrated the occurrence of species HAdV A, C, D, and F, present in faeces of individuals with enteric and non-enteric infections, and JCPyV type 3 (Af2), prevalent in a high genetically mixed population like the Brazilian. The diversity of enteropathogens detected by TAC emphasizes the utility of this methodology for quick assessment of microbiological contamination of the aquatic ecosystems, speeding up mitigation actions where the risk of the exposed population is detected, as well as pointing out the infrastructure gaps in areas where accelerated urban growth is observed.

Urbanization alters coastal plain stream carbon export and dissolved oxygen dynamics

Coastal plain streams in the southeastern United States supply carbon that supports important coastal ecosystems, but the effects of urbanization on carbon export from these streams have not been extensively studied. This study aimed to determine how urbanization changes coastal plain stream organic matter quality, rates of carbon export, and dissolved oxygen dynamics that have implications for stream ecosystem function. Organic matter quality, organic carbon export, and dissolved oxygen concentrations were measured for multiple years (2009 & 2013-2015) in North Carolina coastal plain streams that spanned a gradient of urbanization. Based on spectral characteristics, dissolved organic matter (DOM) quality appeared to shift from characteristic blackwater in minimally impacted streams to clear streamwater in urban streams due to large reductions in chromophoric DOM concentrations, aromaticity, and molecular weight. Differences in spectral indices and characteristics of dissolved organic carbon export suggest that urbanization reduced natural sources of DOM and provided various urban sources of DOM that were likely more bioavailable. Particulate organic matter in the urban streams was indicative of more labile autochthonous sources than that of the less impacted streams, and rates of particulate carbon export increased and shifted to higher flows with watershed impervious surface cover. Diel variation of dissolved oxygen increased with watershed impervious surface cover, indicating that urbanization and associated changes in carbon and nutrient cycling altered stream function. While the effects of urbanization on carbon export were similar to previous studies in other regions, the unique blackwater state of natural streams and receiving waters in the study area make them especially susceptible to negative ecological impacts from altered carbon and nutrient export. Management actions that conserve or restore natural carbon sources to the stream may help mitigate multiple negative effects of urbanization in southeastern US coastal plain streams.

Watershed influences on mercury in tributaries to Lake Ontario

Mercury (Hg) concentrations and speciation were measured in nine tributaries to Lake Ontario as part of two independent field-sampling programs. Among the study tributaries, mean total Hg (THg) concentrations ranged from 0.9 to 2.6 ng/L; mean dissolved Hg (THg_D) ranged from 0.5 to 1.5 ng/L; mean particulate Hg (THg_P) ranged from 0.3 to 2.0 ng/L; and mean methylmercury (MeHg) ranged from 0.06 to 0.14 ng/L. Watershed land cover, total suspended solids (TSS), and dissolved organic carbon (DOC) were evaluated as potential controls of tributary Hg. Significant relationships between THg_D and DOC were limited, whereas significant relationships between THg_P and TSS were common across watersheds. Total suspended solids was strongly correlated with the percentage of agricultural land in watersheds. Particle enrichment of Hg (mass Hg/mass TSS) was highly variable, but distinctly higher in US tributaries likely due to higher TSS in Canadian tributaries associated with higher urban and agricultural land cover. MeHg was largely associated with the aqueous phase, and MeHg as a fraction of THg was positively correlated to percent open water coverage in the watershed. Wetland cover was positively correlated to THg and MeHg concentrations, while urban land cover was only related to higher THg_P.

Determinants of perception on soil erosion and investment in watershed management: Evidence from Awash Basin in Ethiopia

This paper identifies factors affecting perception of soil erosion, investment in soil and water conservation (SWC) on private plots and communal lands, and then preferences of grazing practices influencing watershed management. Using data from a survey of randomly selected 332 households, we employed different econometric tools (ordered probit, binary logit, multinomial logit and bivariate probit) as well as qualitative methods. Results of the ordered probit indicate that provision of training, perception on slope of the plot cultivated, holding of land certification are more likely to influence perception on severity of erosion. The multinomial logit shows different variables affecting the likelihood of practicing a specific SWC measure. Similar set of variables were also used to test their effect on the likelihood of adopting SWC measures on communal land and choice of grazing practices (communal and private). Moreover, coordination failure, and absence of land use plans and policy contributed to poor performance of watershed across the basin. These suggest the need to establish institutional mechanisms to mobilize the youth, introducing an integrated approach, sustained monitoring and evaluation of achievements.

Segmentation of MRI brain scans using spatial constraints and 3D features

This paper presents a novel unsupervised algorithm for brain tissue segmentation in magnetic resonance imaging (MRI). The proposed algorithm, named Gardens2, adopts a clustering approach to segment voxels of a given MRI into three classes: cerebrospinal fluid (CSF), gray matter (GM), and white matter (WM). Using an overlapping criterion, 3D feature descriptors and prior atlas information, Gardens2 generates a segmentation mask per class in order to parcellate the brain tissues. We assessed our method using three neuroimaging datasets: BrainWeb, IBSR18, and IBSR20, the last two provided by the Internet Brain Segmentation Repository. Its performance was compared with eleven well established as well as newly proposed unsupervised segmentation methods. Overall, Gardens2 obtained better segmentation performance than the rest of the methods in two of the three databases and competitive results when its performance was measured by class. Graphical Abstract Brain tissue segmentation using 3D features and an adjusted atlas template.

Source apportionment of water pollutants in the upstream of Yangtze River using APCS-MLR

As the upper reach of the Yangtze River, the Jinsha River has experienced ecological degradation due to increased anthropogenic activities. The potential pollution sources affecting the Jinsha River watershed from 2016 to 2018 were investigated using an improved method in combination with correlation analysis and the absolute principal component score-multiple linear regression receptor modeling technique. Our results identified 5-7 potential pollution sources in the Jinsha main stream watershed and the Pudu, Niulan, and Yalong River watersheds of the Jinsha River. The water pollutant concentrations of the Jinsha main stream watershed were mainly influenced by environmental, agricultural, and human population factors. In the Pudu River watershed, the primary pollution sources changed to natural and sedimentary pollutant sources. It is necessary to control the sedimentary pollutants. The Niulan River watershed was also influenced by natural environment factors. Among those, mineral, sedimentary pollutant, and meteorological sources contributed the most to water quality. In the case of the Yalong River watershed, the influence of non-point source pollution caused by human activities and sedimentary pollutants was the main reason for the deterioration of the ecological environment. The multivariate statistical techniques presented good adaptability for the analysis of pollution sources in the Jinsha River watershed, and the results may be useful for the protection and management of the watershed eco-environment.

The use of multiscale stressors with biological condition assessments: A framework to advance the assessment and management of streams

Incorporating information on landscape condition (or integrity) across multiple spatial scales and over large spatial extents in biological assessments may allow for a more integrated measure of stream biological condition and better management of streams. However, these systems are often assessed and managed at an individual scale (e.g., a single watershed) without a larger regional multiscale context. In this paper, our goals were: (1) To develop a conceptual framework that could combine stream biological condition to abiotic landscape integrity (or, conversely, stressor) data at three spatial scales: watershed, catchment and stream-reach scale, to enable more targeted management actions. Measures of landscape integrity and stressors are negatively related, i.e., integrity on a 0-1 scale is equal or equivalent to stressors on a 1-0 scale. (2) To develop the framework in such a way that allows operational flexibility, whereby different indicators can be used to represent biological condition, and landscape integrity (or stressors) at various scales. (3) To provide different examples of the framework's use to demonstrate the flexibility of its application and relevance to management. Examples include stream biological assessments from different regions and states across the U.S. for fish, macroinvertebrates and diatoms using a variety of assessment tools (e.g., the Biological Condition Gradient (BCG), and an Index of Biotic Integrity (IBI)). Landscape integrity indicators comprise U.S. EPA's nationally available Index of Watershed Integrity (IWI) and Index of Catchment Integrity (ICI), and state and regional derived watershed and stream-reach scale integrity indicators. Scatterplots and a landscape integrity map were used to relate samples of stream condition classes (e.g., good, fair, poor) to watershed, catchment and stream-reach scale integrity. This framework and approach could provide a powerful tool for prioritizing, targeting, and communicating management actions to protect and restore stream habitats, and for informing the spatial extent at which management is applied.

Trade-off between equity and efficiency for allocating wastewater emission permits in watersheds considering transaction

As the management of wastewater emission permits in watershed has become a growing worldwide concern, a substantial challenge has been created in balancing the social stability, economic construction, and ecological function. Therefore, the equitable and efficient allocation of wastewater emission permits in watershed integrating sustainability is vital for environmental management. Considering the wastewater discharge permits transaction between subareas, a multi-objective model is proposed to analyze the allocation of wastewater emission permits in a watershed. The first objective function is to maximize the allocation equity using the environmental Gini coefficient, and the second is to maximize the economic efficiency for the sustainable development of a watershed as the constraint. In this study, the trade-off between the equity and economic efficiency of allocation is balanced. A case study of the Tuojiang River Basin in China is conducted to demonstrate the feasibility, rationality and practicality of the model. The multi-principle and multi-objective allocation model was found to be more reliable and feasible than the previous models, indicating that the equity and efficiency should be balanced to mitigate the water scarcity and deteriorating water quality when managing the basin, and trading is an effective measure for ensuring the equity.

Data for assessment of leached dissolved organic carbon in watersheds

(“Dissolved organic carbon leaching flux in a mixed agriculture and forest watershed in Rwanda” [1]).

This article presents data of leached dissolved organic carbon (LDOC), stream water dissolved organic carbon), rainfall amount (Ra), rainfall intensity (Ri), rainfall soil storage (S), runoff (Q), and soil properties such as total organic carbon (TOC), total nitrogen (TN), cation exchange capacity (CEC), and soil texture data collected in the Rukarara River Watershed (RRW), a tropical watershed. All these data were used to analyze leached dissolved organic carbon (LDOC) fluxes in the watershed and their relationship with stream DOC. LDOC and soil properties data were collected at three sites in multiple plots per site located in natural forest (NF), tea plantations (TP), plantation forests (PF), and croplands (CL). Twenty-three plots in total were sampled to collect LDOC data. Soil properties data were analyzed from soil samples collected nearby the plots. Soil texture elements data were used to calculate soil porosity and saturated hydraulic conductivity (Ks).

Data of stream DOC were analyzed from water samples collected and analyzed in the laboratory using a TOC analyzer. Rainfall data were recorded within the RRW using tipping bucket rain gauges installed at three sites. These rainfall data were used to calculate rainfall intensity, potential surface runoff, and rainfall soil storage.

Assessment of intensive agriculture on water quality in the Culiacan River basin, Sinaloa, Mexico

The percentage of agricultural land cover effect on water quality in Culiacan River basin is studied in this research. The basin contains only intensive cropland as primary economic activity with 60% of the total area. Mathematical relationships between percentages of cropland and total phosphorus (TP) and total nitrogen (TN) concentrations were established. Sampling sites in middle and lower basin and water quality information during 2013-2018 were considered, and percentages of cropland were obtained by geospatial methods including variable area buffers. During rainy season, coefficients of determination were less than 0.2, although quantified nutrient concentration was higher, related to point sources of pollution in the basin. During dry season, coefficients of determination were higher than 0.76 and 0.90 for TN and TP, respectively, with an exponential mathematical trend. Results suggest that intensive agriculture practices generate accelerated loss of soil consolidation, which is transported to water bodies. These soils are in continuous contact with fertilizers and pesticides, mostly organophosphates which have been transported by runoff and underground flows. Using the information generated will help to establish environmental management plans, and to improve environmental diagnosis and effect in countries where there is not enough historical cartographic information and/or water quality data.

Urbanization increases carbon concentration and pCO2 in subtropical streams

Urbanization growth may alter the hydrologic conditions and processes driving carbon concentrations in aquatic systems through local changes in land use. Here, we explore dissolved carbon concentrations (DIC and DOC) along urbanization gradient in Santa Catarina Island to evaluate potential increase of CO₂ in streams. Additionally, we assessed chemical, physical, and biotic variables to evaluate direct and indirect effects of urbanization in watersheds. We defined 3 specific urbanization levels: high (> 15% urbanized area), medium (15-5% urbanized area), and low (< 5% urbanized area) urbanization. The results showed that local changes due to growth of urban areas into watersheds altered the carbon concentrations in streams. DOC and DIC showed high concentrations in higher urbanization levels. The watersheds with an urban building area above 5% showed pCO₂ predominantly above the equilibrium with the atmosphere. These findings reveal that local modifications in land use may contribute to changes in global climate by altering the regional carbon balance in streams.

Where does land use matter most? Contrasting land use effects on river quality at different spatial scales

Understanding the influence of land-use activities on river quality has been a key focus of river monitoring programs worldwide. However, defining which land-use spatial scale is relevant remains elusive. In this study, therefore, we contrasted the influence of land use on river quality using three types of land-use estimators, namely circular buffers around a monitoring site, circular buffers upstream of the monitoring site and the entire watershed area upstream of the monitoring site. The land-use percentage compositions within the Usa-Kikuletwa River catchment in northeastern Tanzania were quantified using Landsat-8 satellite images with a maximum mapping resolution of 30 m. Redundancy analysis models and generalized linear models were used to evaluate the influence of land use on macroinvertebrate assemblages and physico-chemical water quality at different spatial scales in the dry and wet seasons. Overall, a substantial fraction of variation in physico-chemical water quality, macroinvertebrate taxon richness, Chao-1 and TARISS (Tanzania River Scoring System) score could be explained by land use of the entire watershed area upstream of the monitoring site in the dry and wet seasons. However, macroinvertebrate abundances showed strong links with more local land-use patterns within 100 m and 2 km radii. Circular buffers upstream of monitoring sites were more informative for macroinvertebrate assemblages than circular buffers around the monitoring sites. However, the latter did correlate well with physico-chemical water quality variables. Land-use variables correlated across spatial scales (i.e., 100 m up to 2 km radii), but not with the land use in the entire watershed area above the monitoring site. Our results indicate that physico-chemical water quality variables and macroinvertebrates may respond differently to land-uses at different scales. More importantly, our results illustrate that the choice regarding spatial land-use metrics can bias conclusions of environmental impact studies in river systems.

Coupled modeling using PRZM/RICEWQ and SWAT for the North Tiaoxi Watershed

Watershed exposure caused by the use of pesticide in farmland has become a major environmental concern. Currently, there are two major approaches to quantify the watershed exposure: monitoring and modeling. Watershed monitoring is expensive, and short-term monitoring is difficult to be used to address potential long-term exposure variability. Model simulation is widely used because not only can it save time and efforts, but it can also simulate the environmental transport process of pesticide over a long time frame to better understand temporal variability. Research on application of commonly used pesticide exposure assessment models such as PRZM, RICEWQ on watershed scale has found that those models need to be coupled together with waterbody models to assess pesticide exposure at the watershed level, and they are applied on a single crop in targeted area within a watershed, failing to consider the diversity of regional and watershed cropping conditions. To address pesticide exposure assessment in different waterbodies after application on multiple crops within a watershed, this study coupled PRZM, RICEWQ, and SWAT models simultaneously in North Tiaoxi watershed. PRZM model and RICEWQ model were used to simulate the exposure of pesticides in dryland and rice paddies separately, and the pesticide masses through runoff, overflow, spray drift, and other routes simulated by the above two models were set as the input of SWAT model which could simulate hydrology and pollutant transport at watershed scale. Pesticide use, cropping, hydrology, and watershed data were collected, and parameterized for exposure modeling of carbaryl in the North Tiaoxi River after uses on orchard, corn, and rice within the watershed. Model predictions showed high degree of agreement between the simulated results and the field monitoring data. The coupled PRZM, RICEWQ, and SWAT model could simulate reasonably well pesticide exposures in waterbodies with applications on multiple crops within a watershed.

Tradeoffs between agricultural production and ecosystem services: A case study in Zhangye, Northwest China

Humans have increasingly intervened in the nature to advance socioeconomic development at the expense of ecosystem services. Tradeoffs between ecosystem services and socioeconomic development are inevitable and should be considered in sustainable ecosystem management. This is no exception in Zhangye where intensive agricultural activities have significantly affected its ecological conditions. Thus, this study evaluated the tradeoffs between agricultural production and key ecosystem services along with their spatial distributions at the watershed level in Zhangye based on multisource observation data. The key ecosystem services, including net primary productivity (NPP), water yield, and soil conservation, were evaluated for the years 2000, 2010, and 2015 using remote sensing data and the InVEST model. The Morishima elasticity of substitution (MES) between these ecosystem services and agricultural production were then estimated by applying a quadratic directional output distance function, and mapped to determine the tradeoffs. The results showed that the average NPP and annual water yield respectively increased by 22% and 24%, while annual soil conservation decreased by 22% during 2000-2015. The average MES values for agricultural production with NPP, water yield, and soil conservation were 0.14, -0.69, and -0.56, respectively. This indicated the existence of a synergetic relationship between agricultural production and NPP as well as tradeoff relationships between agricultural production and water yield/soil conservation. Differences in the spatial patterns of the relationships between agricultural production and these ecosystem services were observed. Significant tradeoff relationships were observed for agricultural production with water yield and soil conservation in the upper reach of Zhangye. It indicated that increasing agricultural production would be at the cost of decreased water yield and soil conservation, especially in the upper reach area. The quantification and spatial pattern determinations of tradeoffs between ecosystem services and agricultural production is useful for the development of regional ecological conservation policy and sustainable ecosystem management.

Cell Nuclei Segmentation in Cytological Images Using Convolutional Neural Network and Seeded Watershed Algorithm

Morphometric analysis of nuclei is crucial in cytological examinations. Unfortunately, nuclei segmentation presents many challenges because they usually create complex clusters in cytological samples. To deal with this problem, we are proposing an approach, which combines convolutional neural network and watershed transform to segment nuclei in cytological images of breast cancer. The method initially is preprocessing images using color deconvolution to highlight hematoxylin-stained objects (nuclei). Next, convolutional neural network is applied to perform semantic segmentation of preprocessed image. It finds nuclei areas, cytoplasm areas, edges of nuclei, and background. All connected components in the binary mask of nuclei are treated as potential nuclei. However, some objects actually are clusters of overlapping nuclei. They are detected by their outlying values of morphometric features. Then an attempt is made to separate them using the seeded watershed segmentation. If the attempt is successful, they are included in the nuclei set. The accuracy of this approach is evaluated with the help of referenced, manually segmented images. The degree of matching between reference nuclei and discovered objects is measured with the help of Jaccard distance and Hausdorff distance. As part of the study, we verified how the use of a convolutional neural network instead of the intensity thresholding to generate a topographical map for the watershed improves segmentation outcomes. Our results show that convolutional neural network outperforms Otsu thresholding and adaptive thresholding in most cases, especially in scenarios with many overlapping nuclei.

Antibiotic resistance genes, class 1 integrons, and IncP-1/IncQ-1 plasmids in irrigation return flows

Surface waters could be a dominant route by which antibiotic resistance genes (ARGs) are disseminated. In the present study we explored the prevalence and abundance of ARGs [bla_CTX-M-1, erm(B), sul1, tet(B), tet(M), and tet(X)], class 1 integron-integrase gene (intI1), and IncP-1 and IncQ-1 plasmids in eight irrigation return flows (IRFs) and a background site (Main Line Canal, MLC) in the Upper Snake Rock watershed in southern Idaho. Grab samples were collected on a monthly basis for a calendar year, which were processed to extract microbial DNA, followed by droplet digital PCR to quantify the gene copies on an absolute (per 100 mL) and relative (per 16S rRNA gene copies) basis. The antibiotic resistance and intI1 genes and IncP-1/IncQ-1 plasmids were recovered at all IRF sampling sites with detections ranging from 55 to 81 out of 81 water sampling events. The bla_CTX-M-1 gene was detected the least frequently (68%), while the other genes were detected more frequently (88-100%). All of the genes were also detected at MLC from April to Oct when water was present in the canal. The genes from lowest to greatest relative abundance in the IRFs were: bla_CTX-M-1 < erm(B) < tet(B) < IncQ-1 < tet(M) < sul1 < intI1 = IncP-1 < tet(X). When compared to the average annual relative gene abundances in MLC water samples, they were found to be at statistically greater levels (P ≤ 0.008) except that of the IncP-1 and IncQ-1 plasmids (P = 0.8 and 0.08, respectively). The fact that most IRFs contained higher levels than found in the canal water, indicates that IRFs can be a point source of ARGs that ultimately discharge into surface waters.

Torrential flood risk assessment and environmentally friendly solutions for small catchments located in the Romania Natura 2000 sites Ciucas, Postavaru and Piatra Mare

The management of torrential flood risk areas located in natural protected sites requires special approaches. Also, those processes can cause casualties and damage socioeconomic structures (roads, railways, houses, etc.) The processes intercept protected landscapes, sometimes endangering protected species and habitats. The restoration of the streambed's stability in protected areas and the protection of the economic objectives affected by the torrential floods, imply special measures of planning. The planning measures are based on the use of ecological materials and technologies with minimal impact on the environment. The article presents a methodology for identifying small river basins with high torrential risk and the endangered economic objectives, as well as applying this methodology into three Natura 2000 sites from central Romania (ROSCI0207 Postavaru, ROSCI0195 Piatra Mare and ROSCI 0038 Ciucas). Identification of the basins was made considering their geomorphological and hydrological characteristics and the vulnerability of the intercepted socio-economic objectives. Into identified watershed, measurements of the streambed topography and the geometric characteristics of the endangered structures were made. Based on hydraulic simulations, maps were generated for floods with a 100-year return period. Using these flood maps, the maximum water level was determined to highlight the flood risk areas for each socioeconomics structural objective. In areas identified as floodplain, special structural and nonstructural solutions are proposed for guiding water into convenient paths to avoid the endangered structures.

SWAT ungauged: Water quality modeling in the Upper Mississippi River Basin

Improving model performance in ungauged basins has been a chronic challenge in watershed model application to understand and assess water quality impacts of agricultural conservation practices, land use change, and climate adaptation measures in large river basins. Here, we evaluate a modified version of SWAT2012 (referred to as SWAT-EC hereafter), which integrates an energy balanced soil temperature module (STM) and the CENTRUY-based soil organic matter algorithm, for simulating water quality parameters in the Upper Mississippi River Basin (UMRB), and compare it against the original SWAT2012. Model evaluation was performed for simulating streamflow, sediment, and nitrate-N (NO₃-N) and total nitrogen (TN) loadings at three stations near the outlets of UMRB. The model comparison was conducted without parameter calibration in order to assess their performance under ungauged conditions. The results indicate that SWAT-EC outperformed SWAT2012 for stream flow and NO₃-N and TN loading simulation on both monthly and annual scales. For sediment, SWAT-EC performed better than SWAT2012 on a monthly time step basis, but no noticeable improvement was found at the annual scale. In addition, the performance of the uncalibrated SWAT-EC was comparable to other calibrated SWAT models reported in previous publications with respect to sediment and NO₃-N loadings. These findings highlight the importance of advancing process representation in physically-based models to improve model credibility, particularly in ungauged basins.

Chlorophyll-a, dissolved organic carbon, turbidity and other variables of ecological importance in river basins in southern Ontario and British Columbia, Canada

Optical sensing of chlorophyll-a (chl-a), turbidity, and fluorescent dissolved organic matter (fDOM) is often used to characterize the quality of water. There are many site-specific factors and environmental conditions that can affect optically sensed readings; notwithstanding the comparative implication of different procedures used to measure these properties in the laboratory. In this study, we measured these water quality properties using standard laboratory methods, and in the field using optical sensors (sonde-based) at water quality monitoring sites located in four watersheds in Canada. The overall objective of this work was to explore the relationships among sonde-based and standard laboratory measurements of the aforementioned water properties, and evaluate associations among these eco-hydrological properties and land use, environmental, and ancillary water quality variables such as dissolved organic carbon (DOC) and total suspended solids (TSS). Differences among sonde versus laboratory relationships for chl-a suggest such relationships are impacted by laboratory methods and/or site specific conditions. Data mining analysis indicated that interactive site-specific factors predominately impacting chl-a values across sites were specific conductivity and turbidity (variables with positive global associations with chl-a). The overall linear regression predicting DOC from fDOM was relatively strong (R² = 0.77). However, slope differences in the watershed-specific models suggest laboratory DOC versus fDOM relationships could be impacted by unknown localized water quality properties affecting fDOM readings, and/or the different standard laboratory methods used to estimate DOC. Artificial neural network analyses (ANN) indicated that higher relative chl-a concentrations were associated with low to no tree cover around sample sites and higher daily rainfall in the watersheds examined. Response surfaces derived from ANN indicated that chl-a concentrations were higher where combined agricultural and urban land uses were relatively higher.

Ensemble streamflow projections for a small watershed with HSPF model

A watershed modeling tool, Hydrological Simulation Program-FORTRAN (HSPF), was utilized to model the hydrological processes in the agricultural Sarısu watershed in western Turkey. The meteorological input data were statistically downscaled time series from General Circulation Model simulations. The input data were constructed as an ensemble of 400 individual time series of temperature, precipitation, dewpoint temperature, solar radiation, potential evapotranspiration, cloudiness, and wind velocity, as required by HSPF. The ensemble was divided into four subsets, each comprising of 100 time series, of different Special Report on Emissions Scenarios. Yearly and monthly total streamflow time series were obtained from the calibrated and validated HSPF model spanning a period of 116 years between the water years of 1984 and 2099. The projections in the watershed showed a median increase of 3 °C in yearly average temperatures between the beginning and end 30-year periods of the 116-year simulation periods based on 400 ensemble members while the corresponding change in total yearly precipitation was - 71 mm. These changes led to a decrease in yearly streamflows by 40% which reflected itself to varying degrees in monthly flows. Correlations were established between the principal drivers of the watershed hydrological cycle, namely temperature and precipitation, and streamflow. The results showed that the changes in the climatic conditions will greatly affect water-related issues in the watershed and emphasize the necessity of preparing carefully to adapt to a warmer and drier climate.

Exploring ecosystem services and scenario simulation in the headwaters of Qiantang River watershed of China

BACKGROUND

Land use change has a significant impact on ecosystem services in watershed systems. The upper part of Qiantang River, Kaihua Country has experienced land-use changes over the past 15 years, but the effect of these changes on ecosystem services remains unknown.

OBJECTIVE

This study evaluates land-use changes in response to ecological protection and the effects on ecosystem services.

METHODS

Ecosystem services during 2000-2015 are assessed and compared to future land use scenarios in 2025 (business-as-usual, strategic planning, environmental protection, and economic development). These scenarios are identified in collaboration with local stakeholders and used to assess changes in ecosystem services under future scenarios.

RESULTS

Analysis shows that during 2000-2015, the woodland increased by 7335 ha as a result of the "Grain for green" policy, and the built-up land increased by 2259 ha due to urbanization, and these changes affected ecosystem services, such as water yield, nitrogen and phosphorus exports which decreased by 0.29%, 12.45%, and 13.74%, respectively, and soil retention, carbon storage, and habitat quality index increased by 0.05%, 1.36%, and 0.80%, respectively.

CONCLUSION

Among all the future scenarios, the strategic planning scenario is an optimal land use strategy to balance the demand for urban development, while providing higher levels of ecosystem services.

Comparing the effects of climate and land use on surface water quality using future watershed scenarios

Eutrophication of freshwaters occurs in watersheds with excessive pollution of phosphorus (P). Factors that affect P cycling and transport, including climate and land use, are changing rapidly and can have legacy effects, making future freshwater quality uncertain. Focusing on the Yahara Watershed (YW) of southern Wisconsin, USA, an intensive agricultural landscape, we explored the relative influence of land use and climate on three indicators of water quality over a span of 57 years (2014-2070). The indicators included watershed-averaged P yield from the land surface, direct drainage P loads to a lake, and average summertime lake P concentration. Using biophysical model simulations of future watershed scenarios, we found that climate exerted a stronger influence than land use on all three indicators, yet land use had an important role in influencing long term outcomes for each. Variations in P yield due to land use exceeded those due to climate in 36 of 57 years, whereas variations in load and lake total P concentration due to climate exceeded those due to land use in 54 of 57 years, and 52 of 57 years, respectively. The effect of land use was thus strongest for P yield off the landscape and attenuated in the stream and lake aquatic systems where the influence of weather variability was greater. Overall these findings underscore the dominant role of climate in driving inter-annual nutrient fluxes within the hydrologic network and suggest a challenge for land use to influence water quality within streams and lakes over timescales less than a decade. Over longer timescales, reducing applications of P throughout the watershed was an effective management strategy under all four climates investigated, even during decades with wetter conditions and more frequent extreme precipitation events.

Temporal and spatial variability of instream indicator bacteria (Escherichia coli) and implications for water quality monitoring

Many water quality monitoring programs quantify Escherichia coli, an indicator of fecal contamination and potential sewage pollution. However, interpretation of E. coli data can be complex due to abiotic factors that influence its growth and mortality. The goal of this study was to quantify the variability of E. coli in a river and assess the impact of that variability on water quality monitoring study design and sewage pollution source identification. Over 1900 samples were collected and analyzed from 2007 to 2017 in the Norwalk River in Connecticut. Sixty-six percent of the samples collected during weekly to monthly monitoring had E. coli concentrations below 200 CFU/100 mL, indicating that elevated bacteria concentrations were captured infrequently. Patterns observed during daily sampling indicated that the randomization of sampling days within a week may support the identification of pollution sources driven by human behavioral patterns. Spatial autocorrelation in bacteria concentrations was not observed between sites, indicating that the sample locations were not spaced sufficiently close together to be redundant for monitoring. On finer spatial scales however, detection of a known pollution source was found to be challenging at even short distances downstream, with less than 25% of the original source concentration detected at 10 m downstream and less than 10% by 1000 m downstream, suggesting that a high density of study sites may be needed to detect potential sources. These findings can be used to better understand the natural variability of this important indicator organism in freshwater systems, and inform more efficient and effective monitoring.