Hydrobiogeochemistry of Two Catchments in Brazil Under Forest Recovery in an Environmental Services Payment Program

We investigated the fluvial geochemistry of two catchments at different stages in the forest recovery process which have been a focus of an Environmental Services Payment (ESP) program in Brazil. The Posses (PS) and Salto de Cima (SC) catchments (1200 ha and 1500 ha, respectively) are situated in the municipality of Extrema, Minas Gerais state. Their streams flow into the Jaguari River that supplies part of the water demand of the São Paulo metropolitan area. Samples were collected for chemical analysis and physical-chemical field measures every 2 weeks from January to December 2017. An important pollution point source was discovered in the PS stream related to bovine urine and feces, as well another unidentified source that can be related to a small food processing industry and/or a small fish farm. At the SC stream, on the other hand, there was clear evidence of domestic sewage input. This preliminary study confirmed a limited improvement of the stream water quality in response to recovery of the forest vegetation. Therefore, we recommend that in addition to enhanced monitoring to help distinguish biogeochemical sources and the benefits of land conservation practices, the ESP program should consider controlling point source pollution to accomplish its purpose.

Identification of critical areas and evaluation of best management practices using SWAT for sustainable watershed management

Identification of critical erosion-prone areas and selection of best management practices (BMPs) for watersheds are necessary to control their degradation by reducing sediment yields. The current research assesses and proposes a combination of potential BMPs for the Baitarani catchment in India using the Soil and Water Assessment Tool (SWAT). After the successful calibration and validation of the SWAT model developed for this catchment, the model was applied to evaluate the efficacy of eight agricultural and structural management practices and their combinations (three scenarios) for controlling sediment yields at watershed and sub-watershed levels as well as to assess the impacts of combined BMPs on water balance components. A combination of BMPs was found more effective in reducing sediment yields than individual BMPs. Comparative evaluation revealed that structural BMPs (0.66-70%) are better than agricultural BMPs (2-7%) in minimizing sediment yields at watershed level. The costly measures like grade and streambank stabilization structures can reduce the sediment yield up to 70% at the watershed level. The modeling results of the impacts of different combinations of BMPs (three scenarios) indicated that if all the eight BMPs are implemented, the reduction of sediment yields is increased by 76% and 80% at sub-watershed and watershed levels, respectively compared to the Base Scenario. Based on funds availability, a suitable combination of BMPs can be adopted by the concerned decision-makers to effectively reduce sediment yields in the study area. Further, the simulation results of BMPs impacts on water balance components revealed that the annual average surface runoff reduces by 4-14% in the three scenarios, while aquifer recharge (6.8-8.7%), baseflow (8-10.5%), and percolation (1.2-3.9%) increase due to implementation of BMPs. Overall, the findings of this study are very useful for ensuring sustainable management of land and other resources at a catchment scale.

Environmental risk dynamics of pesticides toxicity in a Mediterranean micro-estuary

Pesticides are potentially toxic to aquatic systems, even at low concentration, depending on their individual ecotoxicological properties and their mixture composition. Thus, to evaluate possible ecological stress due to pesticide load, a thorough assessment of the potential toxicity of pesticide mixtures is required. Here we report water discharge and quality data of an eastern Mediterranean micro-estuary (Alexander stream), targeting the temporal distribution of a pesticide mixture. Over 150 water samples were collected during 2 hydrological years representing base-flow and flood conditions. On average, each water sample contained 34 and 45 different pesticides with peak concentrations of 1.4 μg L^-1 of Imidacloprid and 55 μg L^-1 of Diuron during base-flow and flood events, respectively. Pesticide mixtures were potentially toxic to benthic invertebrates and algae during flood events, surpassing the toxicity benchmark with medians of 110% and 155%, respectively. The herbicide Diuron and the insecticide Imidacloprid were the main pesticides responsible for the high potential toxicity during flood events. The falling limb of the flood hydrographs was found to inflict the highest stress on the estuarine environment due to elevated toxicity combined with prolonged residence time of the water. Examination of the potential chronic toxicity of single compounds showed continuous stress for plants, algae, amphibians, crustaceans, insects and fish from nine pesticides. Our data show that the ecosystem of the Alexander micro-estuary is under a continuous chronic stress with acute peaks in potential toxicity during flood events and the period that follows them. We propose that analyzing a small set of flood-tail samples is needed for the evaluation of small estuarine ecosystems risk during the rainy season. From a management perspective, we suggest better control of application practices for Diuron in the watershed to minimize the stress to the estuarine ecosystem.

Modeling seasonal water yield for landscape management: Applications in Peru and Myanmar

A common objective of watershed management programs is to secure water supply, especially during the dry season. To develop such programs in contexts of low data and resource availability, program managers need tools to understand the effect of landscape management on the seasonal water balance. However, the performance of simple, parsimonious models is poorly understood. Here, we examine the behavior of a geospatial tool, developed to map monthly water budgets and baseflow contributions and forming part of the InVEST (integrated valuation of ecosystem services and trade-offs) software suite. The model uses monthly climate, topography, and land-use data to compute spatial indices of groundwater recharge, baseflow, and quickflow. We illustrate the model application in two large basins in Peru and Myanmar, where we compare results with observed data and alternative hydrologic models. We show that the spatial distribution of baseflow contributions correlated well with an established model in the Peruvian basin (r² = 0.81 at the parcel scale). In Myanmar, the model shows an overall satisfactory performance for representing month to month variation (Nash-Sutcliffe-Efficiency 0.6-0.8); however, errors are scale dependent highlighting limitations in representing processes in large basins. Our study highlights modeling challenges, in particular trade-offs between model complexity and accuracy, and illustrates the role that parsimonious models can play to support watershed management programs.

Flood risk attenuation in critical zones of continental Portugal using sustainable detention basins

According to the Floods Directive (Directive 60/2007/EC), the management of floods represents an obligation of each EU member state to defend human lives as well as the economic well-being of societies, especially in areas defined as critical. The purpose of this study was to develop a flood attenuation model based on detention basins in the 23 critical flood risk zones of continental Portugal, capable to eliminate the high and very high flood risk areas instead of attempting to ensure full control of the flood in all potentially threatened areas. The model workflow comprised the sequential use of engineering formulae based on historical peak flows and a zoning algorithm embedded in a Geographic Information System. The formulas allowed to set up the volume of river water to retain in a detention basin during a flood, as well as the smallest catchment area (A) producing this volume. The results were divided into sustainable (h ≤ 8 m) or non-sustainable (h > 8 m) detention basins. Thus, these results indicated the possibility to install 27 sustainable and 75 non-sustainable detention basins in specific catchments within the critical zones contributing watersheds. The number of sustainable detention basins is reduced by about 30% when the full flood control model is used. Because the construction of non-sustainable (engineered) dams is extremely costly, the only possible way to mitigate flood risk in these critical zones would be to couple flood attenuation with hydroelectric use, or through the implementation of an extensive reforestation program in the catchment with the purpose to increase evapotranspiration and reduce runoff.

Valorization of farm pond biomass as fertilizer for reducing basin-scale phosphorus losses

Long-term fertilizer phosphorus (P) inputs are causing phosphorous saturation of agricultural soils globally. The saturation is spreading to the edge-of-the-farm stormwater detention systems (SDSs) from where the legacy P is potentially being released to downstream surface waters. We use site-specific and literature data for P-saturated SDSs, to develop and evaluate the biogeochemical and economic feasibility of a P recycling program that targets both low (LIC, sugarcane) and high intensity cropping (HIC, fresh-produce) systems within a watershed. The focus is to close the P cycle loop to rejuvenate P sink function of SDSs. It involves harvesting and composting the SDS's biomass and it's on-farm use as an organic fertilizer for crops. Results showed that harvesting-composting can conservatively increase the P retention from 50% to 77% for HIC and almost complete treatment for LIC. Beyond potentially increasing yield and improving soil health, compost use can further increase in-field retention of P (and water). Additional costs incurred in harvesting and composting can be offset by the economic value of compost and the reduction in State's expenditure on regional P treatment systems. Treatment costs were $26/kg of P for HIC and $42/kg for LIC, 10 times less than the current state expenditure of $355-$909/kg P using constructed wetlands. We propose an incentivized, payment for services (PS) program, where producers are paid for P recycling. The PS program considers the intensity of cropping systems and their location along the drainage network from headwaters to the outlet, to achieve basin-scale P load reduction. The LIC SDSs recover regional P by passing the public water through them while recycling is implemented at the HIC. The estimated basin-scale P retention with harvest-compost approach was 854 metric tons, 5 times the P that entered the Everglades Protection Area in 2018, at 88%-93% less cost than the State treatment systems.

Prioritizing riparian corridors for ecosystem restoration in urbanizing watersheds

Background

Riparian corridors can affect nutrient, organic matter, and sediment transport, all of which shape water quality in streams and connected downstream waters. When functioning riparian corridors remain intact, they provide highly valued water quality ecosystem services. However, in rapidly urbanizing watersheds, riparian corridors are susceptible to development modifications that adversely affect those ecosystem services. Protecting high quality riparian corridors or restoring low quality corridors are widely advocated as watershed level water quality management options for protecting those ecosystem services. The two approaches, protection or restoration, should be viewed as complementary by watershed managers and provide a foundation for targeting highly functioning riparian corridors for protection or for identifying poorly functioning corridors for restoration. Ascertaining which strategy to use is often motivated by a specific ecosystem service, for example water quality, upon which watershed management is focused. We have previously reported on a spatially explicit model that focused on identifying riparian corridors that have specific characteristics that make them well suited for purposes of preservation and protection focused on water quality. Here we hypothesize that focusing on restoration, rather than protection, can be the basis for developing a watershed level strategy for improving water quality in urbanizing watersheds.

Methods

The model described here represents a geographic information system (GIS) based approach that utilizes riparian characteristics extracted from 40-meter wide corridors centered on streams and rivers. The model focuses on drinking water reservoir watersheds that can be analyzed at the sub-watershed level. Sub-watershed riparian data (vegetation, soil erodibility and surface slope) are scaled and weighted based on watershed management theories for water quality, and riparian restoration scores are assigned. Those scores are used to rank order riparian zones –the lower the score the higher the priority for riparian restoration.

Results

The model was applied to 90 sub-watersheds in the watershed of an important drinking water reservoir in north central Texas, USA. Results from this study area suggest that corridor scores were found to be most correlated to the amount of: forested vegetation, residential land use, soils in the highest erodibility class, and highest surface slope (r² = 0.92, p < 0.0001). Scores allow watershed managers to rapidly focus on riparian corridors most in need of restoration. A beneficial feature of the model is that it also allows investigation of multiple scenarios of restoration strategies (e.g.,  revegetation, soil stabilization, flood plain leveling), giving watershed managers a tool to compare and contrast watershed level management plans.

The value of hydrologic information for watershed management programs: The case of Camboriú, Brazil

Investments in watershed services programs hold the promise to protect and restore ecosystems and water resources. The design and implementation of such programs is often accompanied by hydrologic modeling and monitoring, although the role of hydrologic information in meeting the needs of program managers remains unclear. In the Camboriú watershed, Brazil, we explored the value of hydrologic modeling and monitoring with respect to two dimensions: scientific credibility and use of generated knowledge in the design, implementation, and evaluation of the watershed management program. We used a combination of semi-structured interviews, focus groups, and hydrologic modeling under various levels of data availability to examine when improved models and data availability might build credibility and provide more useful information for decision makers. We found that hydrologic information was not actually used for the detailed design, but rather contributed to broad-scale support of the program by increasing scientific credibility. Model sophistication and data availability improved the credibility of hydrologic information but did not affect actual decisions related to program design. Hydrologic monitoring data were critical for model calibration, and high-resolution land use and land cover data, obtained via remote sensing, affected some model outputs which were not used to design the program. Our study suggests that identifying how hydrologic data will inform decision making should guide the level of effort used in hydrologic modeling and monitoring.

Optimization of management strategies for reducing nitrogen loading in China

Terrestrial Nitrogen (N) loading in the environment has seen a steady increase over the past several decades as a result of more intensive anthropogenic activities. Quantifying N loading for an extended period is important for effective N management. In this study, a statistical model is constructed to describe the relationship between N loading and anthropogenic activities at watershed scale for 211 watersheds covering the entire land area of China. Subsequently, a portfolio optimization model is used to optimize the future management efforts of the long-term N loading. Our results show that N loading in China due to anthropogenic activities has increased significantly over the past 60 years (1949-2010), with the rate of increase at approximately 1 Tg N/year. When designing future N loading management strategies, the next 30 years is divided into three temporal stages and assume that the total amount of expenditure is fixed. The results of portfolio optimization analysis show that the best allocations of management efforts (e.g. capital investments, making new policies, improving technology, or alike) among three temporal stages are 28.55% (2021-2030), 71.45% (2031-2040) and 0 (2041-2050). Furthermore, it is suggested that the future population growth scenario has the largest influence on the results of the portfolio optimization analysis.

Water runoff harvesting systems for restoration of degraded rangelands: A review of challenges and opportunities

Mismanagement of rangelands worldwide has accelerated processes of overland flow and soil erosion, resulting in extensive land degradation. Wherever self-restoration processes of degraded rangelands are hindered or negated, active recovery efforts, coupled with livestock pressure management, might be needed. The objective of this review paper is to provide land managers and environmental planners with applied and practical knowledge on advantages and disadvantages of the main methodologies and practices for runoff harvesting in rangelands. Preferably, restoration efforts should focus on forming low-footprint runoff harvesting systems on hillslopes which encompass the runoff's source area. These systems should imitate natural patchiness, strengthening source-sink relations, accelerating re-establishment of herbaceous and woody vegetation, maximizing the retaining of water on hillslopes, regulating hydrological connectivity, lessening soil erosion, and minimizing transmission of water to stream channels. The resulting lower-energy floods are expected to negate the need for massive check dams in channels. If flood dissipation in streams is still necessary, then high-to medium-porosity check dams, made of local materials, might be effective for lessening scour processes and sediment transport. Furthermore, in terms of environmental sustainability, a large number of pointed (e.g., branch bundles; brush or woody piles; micro-catchments) or low-to medium-footprint lineal means for regulating surface processes in hillslopes (e.g., stone terraces; contour furrows/trenches/ditches) and channels (e.g., log check dams; loose rock check dams; porous or semi-permeable rock check dams; gabions) are expected to be more cost-effective than a small number of massive means (e.g., contour bench terraces; earth bunds/dykes; concrete check dams). If runoff harvesting systems are properly designed, restoration processes over time are expected to generate geo-ecological feedbacks and recover eco-hydrological functioning, increasing pasture productivity and sustaining rangeland carrying capacity.

Impact of forest cover and conservation agriculture on sediment export: A case study in a montane reserve, south-western China

Reforestation and agricultural conservation have long been recognized as important in reducing on-site soil loss and off-site sediment export. Quantitative assessment of their effectiveness is critical, and assists cost-benefit analysis and decision-making in land management and landscape planning. We applied a paired watershed approach to monitor 1-year sediment export in two watersheds with forest-dominated (reference) and mosaic (target) land use in the Naban River Watershed National Natural Reserve (NRWNNR) in Xishuangbanna, south-western China. Analysis of land-use change in the target watersheds showed decreasing total forest cover (FC) (from 57% to 47%), but increasing FC in steep areas (from 54% to 59%) from 2007 to 2012. A distributed hydrological model (Land-Use Change Impact Assessment, LUCIA) was well calibrated and validated through field data from the two watersheds. Scenarios were created representing different FCs (from 31% to 83%) and agricultural management (as-usual and conservation). Simulation results quantified the relation between FC and sediment export as a logarithmic or logit model, indicating at least one turning point of FC, beyond which further forest reduction should significantly increase sediment export. This point was identified in the range between 57% and 61% of the target watershed under as-usual management; it was shifted to 47%-53% by conservation agriculture. Compared with the reference (with 83% FC), conservation agriculture was able to almost fully compensate for increased sediment export by forest reduction to 57% in 2007. However, when forest was reduced further to 47% in 2012, sediment export increased significantly. We concluded that total FC was as important as FC in montane watershed management in steep areas; and crop type conversion, such as rubber to maize in this study, and on-site agriculture management affect more to sediment export than agricultural expansion. We recommend conservation agriculture as an efficient tool for reducing sediment export on a watershed scale.

Coupled effects of climate variability and land use pattern on surface water quality: An elasticity perspective and watershed health indicators

Understanding the coupled effects of climate variability and land use on riverine nitrogen is essential for watershed management. The climate-water relationships for ammonium (NH₄-N) and nitrate (NO₃-N) were determined by an elasticity approach and then the watershed health index was estimated using the reliability, resilience, and vulnerability framework. These methods were applied to an in-situ monitoring dataset of N concentrations measured during 2010-2017 from nine sub-watersheds in the Jiulong River Watershed, China. The results showed that temperature and precipitation elasticity of NH₄-N and NO₃-N changed substantially among various land use patterns. The N concentrations were highly sensitive to extreme climate conditions, particularly at urban and agricultural sub-watersheds. The measure of risk indicators revealed that the watershed health index varied from good health to unhealthy status. Linear regression analysis was used to analyze the interactions among watershed characteristics, climate elasticity, and watershed health. Cropland and population had strong positive correlations with climate elasticity of NO₃-N. Forest and elevation had strong negative associations with climate elasticity of NO₃-N. Watershed health significantly declined with increasing proportion of cropland and population density. This study demonstrated that human-impacted watersheds were less healthy to unhealthy and tend to be more sensitive to climate variability than natural watersheds, which is useful for efforts aimed at improving watershed management.

Flow accumulation based method for the identification of erosion risk points in unpaved roads

The unsuitable construction of unpaved roads has been causing problems related to the formation of erosive processes, sediments in watersheds, bogs, flooding, and holes. Presuming that the areas where flow accumulation intersects unpaved roads represent risk points, our objectives are (1) to develop a qualitative method based on the GIS software management tool (FlowAccRoad) for the identification of the intersection points between flow accumulation and roads and (2) to verify the discrepancy between the points of intersection produced by digital elevation models (DEM) accounting for different spatial resolutions. In the GIS environment, we used the Shuttle Radar Topography Mission (SRTM) and Goiania (GOI) digital elevation models for the modeling of flow accumulation and vectorization of the unpaved roads, both of which are based on the Bandeira Stream Watershed in Goiania, Goiás, Brazil. This highlights that 54 points of intersection between the flow accumulation and unpaved roads present problems related to erosive processes and quagmires, among others. The FlowAccRoad method identified the principal critical points observed in the field, using both the DEM of 30.4 m of spatial resolution (SRTM) and also of 4.8 m of spatial resolution (GOI). From the FlowAccRoad method, we observed that 91% of the risk points identified through the GOI DEM were located less than 20 m from valid points in the field by using GPS. Analyzing the SRTM DEM, only 45% of the critical risk points identified by the method were located less than 20 m from valid points in the field.

Phosphorus mitigation remains critical in water protection: A review and meta-analysis from one of China's most eutrophicated lakes

The processes of urbanization and industrialization within geological phosphorus-rich mountains (GPMn) have resulted in water degradation within southwest China. Lake Dianchi, one of the most eutrophicated lakes in China, has epitomized this issue. Clear understandings of phosphorus (P) mitigation efforts, the evolution of P budgets, and possible risks in the Dianchi system will benefit future eutrophication control, providing valuable lessons for other plateau freshwater lakes. In this study, we applied systematic review methodology to investigate the above questions, and then compared the results with other lakes worldwide. Generally, meta-analytical approaches have indicated P levels remain a key factor in causing algal blooms. Post-2015, the P budget of the Dianchi system, especially in Caohai section, was modified. However, it's still experiencing high pressures from P enrichment (Caohai: 0.4 mg·l^-1; Waihai: 0.2 mg·l^-1). The flux of P in Dianchi remains high, both through the external P load (556 ton·a^-1), and an internal cycle (304 ton·a^-1 associated with the absorption, deposition and removal of algae biomass; and 380 ton·a^-1 associated with sediment exchange). Meanwhile, significant P retention has been observed in the lake, in particular within the Waihai section (211 ton·a^-1). Currently, water diversion (from external watersheds), sewage diversion, and sediment-dredging projects have benefited Dianchi. However, continuous urbanization and GPMn ecological degradation could introduce hundreds of tons of additional P, leading to subsequent algal blooms. Furthermore, beyond Lake Dianchi, other lakes and reservoirs in southwest China are facing similar issues regarding P mitigation, especially in GPMn regions, though corresponding knowledge is still limited. Therefore, effective and flexible sub-regional protection strategies and research related to external and internal P mitigations have become key requirements for Lake Dianchi management. Meanwhile, ecologically sensitive approaches to GPMn regions, as well as city development within basin and market driven treatments, should be incorporated into regional water source protection for southwest China.

Contributions of native forest protection to local water supplies in East Maui

Tropical forests provide a suite of benefits including biodiversity, cultural value, and a range of ecosystem services. Globally, there is increasing interest in incentivizing native forest protection as a multi-benefit natural infrastructure strategy to secure clean and ample water supplies. In addition to conversion to agriculture and other non-forest land uses, non-native species invasion represents a major threat to these systems, particularly on islands. Whereas several recent efforts have quantified the benefits of reforestation or avoided agricultural expansion in tropical forest areas, the hydrologic and associated economic benefits of avoided invasion have received less attention. To address this gap, we quantified the benefits of protecting native forest from conversion to non-native forest in East Maui, Hawai'i in terms of groundwater recharge, a highly valued hydrologic ecosystem service that water utilities increasingly seek to co-finance. Compared with two counterfactual invasion scenarios, the groundwater recharge benefits of planned conservation activities reached 40.9 to 146.3 million cubic meters over 100 years depending on invasion rate assumptions. This translated to 2.70 to 137.6 million dollars of cost savings to the water utility in present value terms (achieved through reducing reliance on more expensive water alternatives) under a range of discount rates and water scarcity assumptions. Our results suggest that investing in native forest conservation provides an important hydrologic ecosystem service benefit that complements the range of benefits provided by these ecosystems. These findings demonstrate that co-financing native forest conservation represents an important supply side option in water resources planning.

Development and application of GIS-based assessment of land-use impacts on water quality: A case study of the Kharaa River Basin

Effective analytical tools, such as geographical information systems (GIS) and multivariate analysis, help to deal with spatial data and complex interactions in watershed management. To investigate the impact of land-use on chemical water quality in the Mongolian Kharaa River Basin, the whole catchment and sub-catchments in relation to each sampling point were delineated. Chemical water quality over three seasons was assessed with GIS and RDA in a modeling approach with forward selection of variables and cluster analysis. The most powerful predictors of river water quality were altitude, settlements, forest, cropland, and distance to spring. In particular, this was true when instead of full sub-basins riparian buffer zones (max. 3 km) were considered. From a management perspective, this implies that the protection of riparian zones should be a priority in the Kharaa basin and similar river basins in Mongolia and Central Asia. Because of its positive effects on water quality, forest protection should be closely coupled with river basin management.

Predicting Farmer Adoption of Water Conservation Practices Using a Norm-based Moral Obligation Model

This study examines the social-psychological drivers of conservation practice adoption among farmers in Minnesota. Specifically, it applies a moral obligation model to understand farmer decision-making related to water resource management, focusing in particular on conservation tillage and drainage management. Data were collected through a self-administered mail survey of 1500 landowners in two subwatersheds of the Red River Basin: Wild Rice River and Middle Snake-Tamarac Rivers. Data were analyzed using structural equation modeling. Study results demonstrate that farmers' decisions to adopt conservation practices are influenced by personal norms and perceived ability to protect water resources. Further, beliefs about personal responsibility for water protection, and perceived ability to protect water resources activate personal norms of water protection. Collectivistic and biosphere-altruistic values serve as the basis for the activation of personal norms. Study findings suggest that a combination of behavioral intervention strategies that provide tailored information about local water resource problems, appeal to farmers' values, sense of responsibility and personal obligation, and enhance farmers' ability to use conservation practices may be effective in achieving higher levels of conservation practice adoption.

Effects of dissolved organic matter from different sources on Microcystis aeruginosa growth and physiological characteristics

The roles dissolved organic matter play when managing watersheds and controlling cyanobacteria blooms have been overlooked. We assessed the effects of dissolved organic matter extracted from biochar, paddy soil, pectin, and rice husks, at carbon concentrations of 0, 1, 3, 5, and 10 mg L^-1 on Microcystis aeruginosa growth, photosynthesis, and physiological characteristics. The dissolved organic matter derived from paddy soil and rice husks increased M. aeruginosa growth by promoting photosynthesis. Biochar at low carbon concentrations (1, 3, and 5 mg L^-1) also improved M. aeruginosa growth by increasing the maximum photosynthesis II quantum yield. However, biochar at a high concentration decreased the protein and RNA concentrations in M. aeruginosa and therefore inhibited the increase in M. aeruginosa biomass. Pectin did not affect M. aeruginosa photosynthesis, protein concentration, RNA concentration, or growth. The results suggested that M. aeruginosa growth was improved by the amino acids tryptophan and tyrosine, decreased by abundant humic-acid-like substances, and unaffected by polysaccharides.

Quantification of tributaries contributions using a confluence-based sediment fingerprinting approach in the Canche river watershed (France)

Since a few years, land use management aims to reduce and control water erosion processes in watersheds but there is a lack of quantitative information on the contribution of the sources of transported sediment. This is most important in agricultural areas where soils are sensitive to erosion. The geology of these areas is often characterized by large expanses of relatively homogeneous quaternary silts. The possibility of distinguishing the sources of erosion according to their geological substratum is thus very delicate. This information is important because its lack can lead to the mis-implementation of erosion control measures. To address this request, a confluence-based sediment fingerprinting approach was developed on the Canche river watershed (1274 km²; northern France), located in the European loess belt, an area that is affected by diffuse and concentrate erosion processes. Suspended particulate matter was collected during five seasonal sampling campaigns using sediment traps at the outlet of each tributary and confluence with the main stream of the Canche river. The final composite fingerprint was defined using physico-chemical and statistical analyses. The best tracer parameters for each tributary were selected using stepwise discriminant function analyses. These parameters were introduced into a mass balance mixing model incorporating Monte-Carlo simulations to represent the uncertainty. Estimates of the overall mean contributions from each tributary were quantified at different temporal scales. The annual sediment flux tributaries contributions range from 3 to 22% at the outlet of the Canche river, and annual sediment flux range from 0.87 to 40.7 kt yr^-1. The Planquette and the Créquoise tributaries appear to be those producing the largest sediment flux. In contrast, tributaries with the highest number of erosion control on their area exhibit the lowest values of sediment flux. Our results indicate a positive impact of recent land management policies in the Canche river watershed.

Returns on investment in watershed conservation: Application of a best practices analytical framework to the Rio Camboriú Water Producer program, Santa Catarina, Brazil

Watershed management may have widespread potential to cost-effectively deliver hydrologic services. Mobilizing the needed investments requires credible assessments of how watershed conservation compares to conventional solutions on cost and effectiveness, utilizing an integrated analytical framework that links the bio-, litho-, hydro- and economic spheres and uses counterfactuals. We apply such a framework to a payment for watershed services (PWS) program in Camboriú, Santa Catarina State, Brazil. Using 1 m resolution satellite imagery, we assess recent land use and land cover (LULC) change and apply the Land Change Modeler tool to predict future LULC without the PWS program. We use current and predicted counterfactual LULC, site costs and a Soil and Water Assessment Tool model calibrated to the watershed to both target watershed interventions for sediment reduction and predict program impact on total suspended solids (TSS) concentrations at the municipal water intake-the principal program objective. Using local water treatment and PWS program costs, we estimate the return on investment (ROI; benefit/costs) of the program. Program ROI exceeds 1 for the municipal water utility in year 44, well within common drinking water infrastructure planning horizons. Because some program costs are borne by third parties, over that same period, for overall (social) program ROI to exceed 1 requires delivery of very modest flood and supply risk reduction and biodiversity co-benefits, making co-benefits crucial for social program justification. Transaction costs account for half of total program costs, a result of large investments in efficient targeting and program sustainability. Co-benefits justify increased cost sharing with other beneficiaries, which would increase ROI for the utility, demonstrating the sensitivity of the business case for watershed conservation to its broader social-economic case and the ability to forge institutional arrangements to internalize third-party benefits.

Half century change of interactions among ecosystem services driven by ecological restoration: Quantification and policy implications at a watershed scale in the Chinese Loess Plateau

The concept of Ecosystem Service (ES) has provided an underpinning framework for ecological restoration research and applications. Ecological restoration is a corrective intervention that aims to reverse land degradation and to contribute to the 2030 Global Sustainable Development goal of Land Degradation Neutrality. It is critical to investigate the long-term effects of ecological restoration and land use change on ESs and ES interactions (synergies or trade-offs) to better understand the mechanisms supporting this goal. This paper describes an analysis of land use and ESs using historical data for a typical watershed in Chinese Loess Plateau, which has experienced series of restoration activities since the 1950s. Six important ESs (food provisioning, soil retention, hydrological regulation, carbon sequestration, water purification and habitat provisioning for biodiversity) were quantified at eight intervals between 1958 and 2015. The interactions between ESs were evaluated by correlation analysis. The results show that soil retention, carbon sequestration, water purification and habitat provisioning for biodiversity increased significantly across the different land use types over several decades but not hydrological regulation. The relationship between ESs was found to be variable over different time periods and a transition point between 1990 and 1995 was identified. Grassland was found to maintain greater water yield than woodland with high values of other ESs. The results suggest that trade-offs between ESs can be mitigated by adjusting the proportion of some important land use types (such as woodland and grassland).

Identifying representative watershed for the Urmia Lake Basin, Iran

Designation of representative watersheds (RWs) as a reference area representing key behavior of the whole region is an essential tool to provide a time and cost-effective basis for monitoring watershed performance against different driving forces. It is more important in developing countries facing lack of necessary investments in one hand and ever-increasing human interventions and need to assess the outcome behavior of the system in another hand. However, this serious affair has been less considered worldwide, in general, and in developing countries, in particular. Therefore, in the present study, a quantitative-based method of Representative Watershed Index (RWI) with potential range from 0 to 100 has been formulated using four important criteria and available national-wide raster data of elevation (meter), slope (%), rainfall erosivity factor (t m ha^-1 cm h^-1), and land use. The approach was then applied to the data prepared for the unique and invaluable global water ecosystem of the Urmia Lake Basin (ULB), north-western Iran, as a case study. The input raster was overlaid via matrices programming in the MATrix LABoratory (MATLAB) 2016 and Geographic Information System (GIS) 9.3 software environments. The RWIs were accordingly computed for 61 sub-watersheds of the ULB. The RWIs resulted from quadri-partite dimensional matrices that varied from 5.54 to 53.46 with respective maximum dissimilarity and resemblance with the entire 61 study sub-watersheds in the region. However, the sub-watershed with RWI of 40.65 (No. 57) was proposed as the final RW for the whole ULB due to hydrological independency, appropriate locality, and existence of functioning meteorological and hydrometric stations. The identified RW would be suggested to be considered as the basis for future insight monitoring and assessing environmental issues for the region eventually leading to an appropriate adaptive watershed management. Graphical abstract ᅟ.

Bed and suspended sediment-associated rare earth element concentrations and fluxes in a polluted Brazilian river system

Rare earth elements (REEs) have been recently recognized as emergent pollutants in rivers. However, data regarding REE fluxes in association with either bed or suspended are scarce. To address this knowledge gap, we determined the concentrations and fluxes of La, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Lu, Dy, Er, Ho, Tb, and Tm in bed and suspended sediment samples of a representative polluted Brazilian River. Sediment-associated data on REEs were placed in the context of corresponding background concentrations in soils under natural conditions along the Ipojuca watershed. Light rare earth elements (LREEs) comprised more than 94% of the total REEs associated with bed and suspended sediments. Suspended sediments accounted for more than 95% of the total REE flux. The Ce and Nd fluxes of about 7 t year^-1 underscore the importance of including REEs in future estimations of global suspended sediment-associated element fluxes. In contrast, bedload often transported less than 0.0007 t year^-1 of each REE. The main sources of pollution in the Ipojuca River are anthropogenic, likely due to domestic effluent and waste water from industrial and agricultural operations-major causes of sediment-associated Gd transport in polluted streams.

Embedding co-production and addressing uncertainty in watershed modeling decision-support tools: successes and challenges

Decision-support tools (DSTs) are often produced from collaborations between technical experts and stakeholders to address environmental problems and inform decision making. Studies in the past two decades have provided key insights on the use of DSTs and the importance of bidirectional information flows among technical experts and stakeholders - a process that is variously referred to as co-production, participatory modeling, structured decision making, or simply stakeholder participation. Many of these studies have elicited foundational insights for the broad field of water resources management; however, questions remain on approaches for balancing co-production with uncertainty specifically for watershed modeling decision support tools. In this paper, we outline a simple conceptual model that focuses on the DST development process. Then, using watershed modeling case studies found in the literature, we discuss successful outcomes and challenges associated with embedding various forms of co-production into each stage of the conceptual model. We also emphasize the "3 Cs" (i.e., characterization, calculation, communication) of uncertainty and provide evidence-based suggestions for their incorporation in the watershed modeling DST development process. We conclude by presenting a list of best practices derived from current literature for achieving effective and robust watershed modeling decision-support tools.

Hybrid modeling approach for the northern Adriatic watershed management

Northern Adriatic (NA) is one of the most productive parts of the Mediterranean Sea due to vast nutrient discharges from the contributing watershed. To understand better the excess of nutrients as stressors to the state of the marine ecosystem, a hybrid modeling approach following the DPSIR framework and terminology was developed, linking: 1) the AVGWLF model for modeling the pressures, i.e. nutrients originating from the watershed caused by two major drivers (urbanization and agriculture), 2) the ML tool MTSMOTI for inducing a model tree connecting the pressures with the marine ecosystem state, and 3) the water quality index, TRIX, equation to evaluate the trophic state of the marine ecosystem. Data used for the modeling purpose comprised GIS layers (i.e., digital terrain model, land use/cover data, soil map, locations of hydro-meteorological stations and WWTPs), time series data (i.e., hydro-meteorological data and nutrient concentrations), and statistical data (i.e., number of inhabitants, connections to wastewater treatment, livestock statistics, etc.) as well as physical, chemical and biological parameters, measured at six marine water monitoring stations, located between the Po River delta (Italy) and the city of Rovinj (west Istrian coast, Croatia). Using the model, seven watershed management scenarios related to wastewater treatment and agricultural activities were evaluated for their influence on the state of the NA marine ecosystem. According to the results, the gradual implementation of the UWWTD in the last 10years contributed significantly to the preservation and improvement of the NA marine ecosystem state. However, despite the full implementation of the UWWTD, the state of the NA marine ecosystem could deteriorate in case of increased nutrient loads from agriculture. Since the UWWTD is already close to its full implementation, NA watershed management should focus on controlling agricultural activities in order to maintain 'high' state of the NA marine ecosystem.