Impacts of Land Use on Surface Water Quality in a Subtropical River Basin: A Case Study of the Dongjiang River Basin, Southeastern China

Heavy metals in tributaries of Tiber River in the urban area of Rome (Italy)

Both natural and anthropogenic activities are responsible for heavy metal abundance in the environment. Due to the high persistence, heavy metals can accumulate and remain in the sediment for very long periods, becoming a source of contaminants for aquatic biota. Within small urbanized watercourse catchments, the accumulation of heavy metals in bottom sediments takes place and sediments can be adopted as an efficient indicator for monitoring heavy metal pollution levels and pollution sources in aquatic environments. Tiber River, the most polluted river among the 20 longest Italian rivers, has different tributaries distributed from north to south of Rome city. The aim of the study was to evaluate the heavy metal pollution in water and sediment of six Tiber River small tributaries through the use of land cover, water physico-chemical parameters and geochemical multi-index (Concentration factor, Pollution Load index, Enrichment factor and Geoaccumulation index). The results indicate that in general the contamination of water and sediments is moderate as the threshold values are exceeded only by some metals and in some sites. As regards the indices that evaluate the enrichment factors, it has been seen that some sampling sites have high values of specific metal enrichment (As, Hg, Pb). A more compromised situation is highlighted by the Concentration Factor and the Pollution Load index where more than half of the sampling sites are found at levels of significant heavy metal pollution suggesting that point sources of heavy metals in the water and sediments should be closely monitored by the use of combined analysis.

Differentiated cognition of the effects of human activities on typical persistent organic pollutants and bacterioplankton community in drinking water source

Accelerated urbanization in developing countries led to a typical gradient of human activities (low, moderate and high human activities), which affected the pollution characteristics and ecological functions of aquatic environment. However, the occurrence characteristics of typical persistent organic pollutants, including organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), and bacterioplankton associated with the gradient of human activities in drinking water sources is still lacking. Our study focused on a representative case - the upper reaches of the Dongjiang River (Pearl River Basin, China), a drinking water source characterized by a gradient of human activities. A comprehensive analysis of PAHs, OCPs and bacterioplankton in the water phase was performed using gas chromatography-mass spectrometry (GC-MS) and the Illumina platform. Moderate human activity could increase the pollution of OCPs and PAHs due to local agricultural activities. The gradient of human activities obviously influenced the bacterioplankton community composition and interaction dynamics, and low human activity resulted in low bacterioplankton diversity. Co-occurrence network analysis indicated that moderate human activity could promote a more modular organization of the bacterioplankton community. Structural equation models showed that nutrients could exert a negative influence on the composition of bacterioplankton, and this phenomenon did not change with the gradient of human activities. OCPs played a negative role in shaping bacterioplankton composition under the low and high human activities, but had a positive effect under the moderate human activity. In contrast, PAHs showed a strong positive effect on bacterioplankton composition under low and high human activities and a weak negative effect under moderate human activity. Overall, these results shed light on the occurrence characteristics of OCPs, PAHs and their ecological effects on bacterioplankton in drinking water sources along the gradient of human activities.

Examining chlorophyll-a concentrations in tropical reservoirs under various land use changes using Sentinel - 2 and Google Earth engine - Bhadra and Tungabhadra, India

The understanding of spatio-temporal variation in land use and land cover (LULC) patterns is crucial for managing catchment land use planning, as it directly influences of tropical reservoir water quality and the subsequent Nutrient Contamination (NC) of unmonitored water bodies. The current research attempts to accurately measure the influence of LULC and its associated determinants on the quantities of NC loads by using Chl-a as a proxy, within tropical reservoirs, i.e. Bhadra and Tungabhadra, located in same river catchment. This Chl-a spread calculated by the Maximum Chlorophyll Index (MCI) derived from Sentinel 2 satellite data products covering the period from July 2016 to June 2021 were done using Google Earth Engine (GEE) platform. The validation analysis confirms the robustness of the methodology with a strong correlation between MCI-calculated values and EOMAP (Earth Observation and Environmental Services Mapping) Chl-a (μg/L) data points for both reservoirs, Bhadra (R2 = 0.64) and Tungabhadra (R2 = 0.68). The findings reveal that, Tungabhadra reservoir consistently exhibits an excessive spatial distribution of Chl-a spread area (17 km2 to 335 km2), reflecting nutrient-rich water inflows, particularly evident during the post-monsoon period. This notable rise could be linked to harvesting the Kharif crop, resulting in elevated nutrient concentrations. In contrast Bhadra reservoir, dominated by forested areas, maintains relatively lower Chl-a spread areas (<20 km2), highlighting its pivotal role in maintaining water cleanliness and serves as a riparian boundary. In addition, the changes in LULC classes show a strong relationship with variation in Chl-a during the studied period, for the Bhadra Reservoir R2 = 0.51 (F- statistics = 3.983, p = 0.021), and the Tungabhadra Reservoir R2 = 0.802 (F- statistics = 7.489, p = 0.0143). This highlights how changes in land use significantly shape contamination dynamics, deepening our understanding of nutrient inputs and contamination drivers in tropical reservoirs.

Spatiotemporal drivers of urban water pollution: Assessment of 102 cities across the Yangtze River Basin

Effective management of large basins necessitates pinpointing the spatial and temporal drivers of primary index exceedances and urban risk factors, offering crucial insights for basin administrators. Yet, comprehensive examinations of multiple pollutants within the Yangtze River Basin remain scarce. Here we introduce a pollution inventory for urban clusters surrounding the Yangtze River Basin, analyzing water quality data from 102 cities during 2018-2019. We assessed the exceedance rates for six pivotal indicators: dissolved oxygen (DO), ammonia nitrogen (NH3-N), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total phosphorus (TP), and the permanganate index (CODMn) for each city. Employing random forest regression and SHapley Additive exPlanations (SHAP) analyses, we identified the spatiotemporal factors influencing these key indicators. Our results highlight agricultural activities as the primary contributors to the exceedance of all six indicators, thus pinpointing them as the leading pollution source in the basin. Additionally, forest coverage, livestock farming, chemical and pharmaceutical sectors, along with meteorological elements like precipitation and temperature, significantly impacted various indicators' exceedances. Furthermore, we delineate five core urban risk components through principal component analysis, which are (1) anthropogenic and industrial activities, (2) agricultural practices and forest extent, (3) climatic variables, (4) livestock rearing, and (5) principal polluting sectors. The cities were subsequently evaluated and categorized based on these risk components, incorporating policy interventions and administrative performance within each region. The comprehensive analysis advocates for a customized strategy in addressing the discerned risk factors, especially for cities presenting elevated risk levels.

Modelling relationships between land use and water quality using statistical methods: A critical and applied review

Land use/land cover (LULC) can have significant impacts on water quality and the health of aquatic ecosystems. Consequently, understanding and quantifying the nature of these impacts is essential for the development of effective catchment management strategies. This article provides a critical review of the literature in which the use of statistical methods to model the impacts of LULC on water quality is demonstrated. A survey of these publications, which included hundreds of original research and review articles, revealed several common themes and findings. However, there are also several persistent knowledge gaps, areas of methodological uncertainty, and questions of application that require further study and clarification. These relate primarily to appropriate analytical scales, the significance of landscape configuration, the estimation and application of thresholds, as well as the potentially confounding influence of extraneous variables. Moreover, geographical bias in the published literature means that there is a need for further research in ecologically and climatically disparate regions, including in less developed countries of the Global South. The focus of this article is not to provide a technical review of statistical techniques themselves, but to examine important practical and methodological considerations in their application in modelling the impacts of LULC on water quality.

Effect of urbanization and urban forests on water quality improvement in the Yangtze River Delta: A case study in Hangzhou, China

In the context of rapid global urbanization, the sustainable development of ecosystems should be considered. Accordingly, the Planetary Boundaries theory posits that reducing the amount of nitrogen and phosphorus pollutants entering bodies of water is necessary as excess levels may harm the aquatic environment and reduce in water quality. Thus, based on the long-term monitoring data of representative urban rivers in the Yangtze River Delta region, we evaluated the nitrogen and phosphorus pollution of water bodies in different urbanization stages and further quantified the effect of urban forests on water quality improvement. The results showed that, with the continuous progression of urbanization, the proportion of impervious surface area increased, along with the levels of nitrogen and phosphorus pollution in water bodies. The critical period of water quality deterioration in urban rivers occurred during the medium urbanization level when the proportion of impervious surface area reached 55-65 %, and the probability of an abrupt increase in total nitrogen (TN) and total phosphorus (TP) concentration exceeded 95 %. However, increasing the area of urban forests during this period reduced TN pollution by 36.64 % and TP pollution by 49.03 %. The results of this study support the expansion of urban forests during the medium urbanization stage to improve water quality. Furthermore, our results provide a reference and theoretical basis for urban forest construction as a key aspect of the sustainable development of the urban ecosystem in the Yangtze River Delta and similar regions around world.

The combined effects of treated sewage discharge and land use on rivers

Freshwater ecosystems are increasingly threatened by multiple anthropogenic stressors. Release of treated sewage effluent and pollution from agricultural or urban sources can independently reduce water quality with implications for ecological communities. However, our knowledge of the combined effects of these stressors is limited. We performed a field study to quantify the combined effect of treated sewage discharge and land use on nutrient concentrations, sewage fungus presence and communities of macroinvertebrates and benthic algae. Over three seasons in four rivers we found that a model which included an interaction between sewage pollution and time of the year (i.e. months) was the best predictor of nutrient concentrations and the abundance of algae and sewage fungus. Both macroinvertebrate and algae communities shifted downstream of sewage input. Specifically, more tolerant groups, such as cyanobacteria and oligochaetes, were more abundant. The EPT (Ephemeroptera, Plecoptera and Tricoptera) water quality score was best explained by an interaction between month and agriculture in the surrounding landscape. Overall, our results show that sewage discharge has a significant impact on water quality and benthic riverine communities, regardless of the surrounding land uses. Agricultural inputs, however, could be more important than treated sewage discharge in reducing the abundance of sensitive invertebrate taxa. We need both improvements to wastewater treatment processes and reductions in agricultural pollution to reduce threats to vulnerable freshwater communities.

Convergence in Perceptions of Ecosystem Services Supports Green Infrastructure Decision-making in a Semi-arid City

Effective management of cities using ecosystem services from green infrastructure (GI) requires explicit consideration of the linkages between provision of services and ecosystem service demands (i.e., governance priorities). Identification of stakeholder knowledge and objectives in GI decision-making contexts with respect to ecosystem services may improve urban planning; yet this information is rarely explicit in local contexts and cases. We address this gap by surveying environmental stakeholders and practitioners to investigate how perceptions of ecosystem services influence GI practice in Tucson, AZ. Results indicate that the semi-arid environment and urban design led to prioritizations that focus on water sustainability and urban heat mitigation. We found strong agreement in environmental perceptions between different management sectors. We observed matches (as well as mismatches) between the ecosystem service priorities and important environmental issues. Ecosystem services prioritization revealed a unique classification of ecosystem services that reflects stakeholder priorities. Our findings suggest the study of ecosystem services supply and demand can inform local urban management. These findings from a semi-arid city further suggest that understanding stakeholder knowledge, perceptions, and priorities should be important for cities in other regions where GI is being implemented as an environmental solution to provide ecosystem services.

Assessing the impact of land use and land cover on river water quality using water quality index and remote sensing techniques

The impact of land use on water quality is becoming a global concern due to the increasing demand for freshwater. This study aimed to assess the effects of land use and land cover (LULC) on the surface water quality of the Buriganga, Dhaleshwari, Meghna, and Padma river system in Bangladesh. To determine the state of water, water samples were collected from twelve locations in the Buriganga, Dhaleshwari, Meghna, and Padma rivers during the winter season of 2015 and collected samples were analysed for seven water quality indicators: pH, temperature (Temp.), conductivity (Cond.), dissolved oxygen (DO), biological oxygen demand (BOD), nitrate nitrogen (NO₃-N), and soluble reactive phosphorus (SRP) for assessing water quality (WQ). Additionally, same-period satellite imagery (Landsat-8) was utilised to classify the LULC using the object-based image analysis (OBIA) technique. The overall accuracy assessment and kappa co-efficient value of post-classified images were 92% and 0.89, respectively. In this research, the root mean squared water quality index (RMS-WQI) model was used to determine the WQ status, and satellite imagery was utilised to classify LULC types. Most of the WQs were found within the ECR guideline level for surface water. The RMS-WQI result showed that the "fair" status of water quality found in all sampling sites ranges from 66.50 to 79.08, and the water quality is satisfactory. Four types of LULC were categorised in the study area mainly comprised of agricultural land (37.33%), followed by built-up area (24.76%), vegetation (9.5%), and water bodies (28.41%). Finally, the Principal component analysis (PCA) techniques were used to find out significant WQ indicators and the correlation matrix revealed that WQ had a substantial positive correlation with agricultural land (r = 0.68, P < 0.01) and a significant negative association with the built-up area (r =  - 0.94, P < 0.01). To the best of the authors' knowledge, this is the first attempt in Bangladesh to assess the impact of LULC on the water quality along the longitudinal gradient of a vast river system. Hence, we believe that the findings of this study can support planners and environmentalists to plan and design landscapes and protect the river environment.

Nitrogen and phosphorus spatio-temporal distribution and fluxes intensifying eutrophication in three tropical rivers of Côte d'Ivoire (West Africa)

Nutrient contamination assessments in the three West African tropical Comoé, Bandama, and Bia Rivers (Côte d'Ivoire) were performed from March 2016 to March 2018. Five stations per river were sampled. Nutrients spatio-temporal distributions were mapped and showed nitrogen concentrations (nitrite 0.001 to 0.025 mg/L NO₂^--N, and nitrate 0.26 to 3.60 mg/L NO₃^--N) increased significantly with rainfall contrary to phosphorus (0.01 to 0.12 mg/L P). The Chl-a and TSI_tsr data revealed the hypereutrophic status of rivers. Moreover, N:P mass ratio suggests nitrogen as the main limiting factor of primary production during the low (March) and high flow periods (October-November), while phosphorus is the limiting factor in June, at the high flow beginning. The land uses around watersheds were the main sources of phosphorus and nitrogen enhancing the rivers' eutrophication. Phosphorus and nitrogen fluxes were related to leaching river catchments and were significant sources of nutrients to the Atlantic Ocean.

Insights from the Niger Delta Region, Nigeria on the impacts of urban pollution on the functional organisation of Afrotropical macroinvertebrates

Anthropogenic activities, including urbanisation and industrialisation threaten stream ecological integrity, ecosystem community structure and ecosystem functioning of rivers and streams worldwide. However, developing sustainable monitoring strategies for ecological health remains a critical challenge in Africa. We examined the effects of urban disturbance on macroinvertebrate Functional Feeding Groups in selected streams in the Niger Delta Region of Nigeria. We sampled 11 sites between 2008 and 2012 and grouped into three site groups (Site groups 1 > 2 > 3). The groups represent an increasing gradient of urban pollution. Our result showed that urban-induced disturbances affected physicochemical variables in the study area (PERMANOVA; p < 0.05), with nutrients NO₂-N, PO₄-P, and electrical conductivity being significantly higher in impacted Site group 3 (ANOVA, p < 0.05). Predators and gatherers were the most dominant Functional Feeding Group recorded in the study area, while shredders were the least abundant macroinvertebrate Functional Feeding Groups. The multivariate RLQ analysis revealed that shredders, predators, and scrapers were tolerant of urban pollution, whereas gatherers were sensitive to increasing urban pollution. Overall, macroinvertebrates Functional Feeding Groups responded differentially to urban pollution in the Niger Delta Region. Identifying pollution indicator Functional Feeding Groups is seen as an important step towards developing a reliable, low-cost tool for riverine monitoring of urban pollution effects in Africa.

What is the relationship between land use and surface water quality? A review and prospects from remote sensing perspective

Good surface water quality is critical to human health and ecology. Land use determines the surface water heat and material balance, which cause climate change and affect water quality. There are many factors affecting water quality degradation, and the process of influence is complex. As rivers, lakes, and other water bodies are used as environmental receiving carriers, evaluating and quantifying how impacts occur between land use types and surface water quality is extremely important. Based on the summary of published studies, we can see that (1) land use for agricultural and construction has a negative impact on surface water quality, while woodland use has a certain degree of improvement on surface water quality; (2) statistical methods used in relevant research mainly include correlation analysis, regression analysis, redundancy analysis, etc. Different methods have their own advantages and limitations; (3) in recent years, remote sensing monitoring technology has developed rapidly, and has developed into an effective tool for comprehensive water quality assessment and management. However, the increase in spatial resolution of remote sensing data has been accompanied by a surge in data volume, which has caused difficulties in information interpretation and other aspects.

Humans and Hoofed Livestock Are the Main Sources of Fecal Contamination of Rivers Used for Crop Irrigation: A Microbial Source Tracking Approach

Freshwater bodies receive waste, feces, and fecal microorganisms from agricultural, urban, and natural activities. In this study, the probable sources of fecal contamination were determined. Also, antibiotic resistant bacteria (ARB) were detected in the two main rivers of central Chile. Surface water samples were collected from 12 sampling sites in the Maipo (n = 8) and Maule Rivers (n = 4) every 3 months, from August 2017 until April 2019. To determine the fecal contamination level, fecal coliforms were quantified using the most probable number (MPN) method and the source of fecal contamination was determined by Microbial Source Tracking (MST) using the Cryptosporidium and Giardia genotyping method. Separately, to determine if antimicrobial resistance bacteria (AMB) were present in the rivers, Escherichia coli and environmental bacteria were isolated, and the antibiotic susceptibility profile was determined. Fecal coliform levels in the Maule and Maipo Rivers ranged between 1 and 130 MPN/100-ml, and 2 and 30,000 MPN/100-ml, respectively. Based on the MST results using Cryptosporidium and Giardia host-specific species, human, cattle, birds, and/or dogs hosts were the probable sources of fecal contamination in both rivers, with human and cattle host-specific species being more frequently detected. Conditional tree analysis indicated that coliform levels were significantly associated with the river system (Maipo versus Maule), land use, and season. Fecal coliform levels were significantly (p < 0.006) higher at urban and agricultural sites than at sites immediately downstream of treatment centers, livestock areas, or natural areas. Three out of eight (37.5%) E. coli isolates presented a multidrug-resistance (MDR) phenotype. Similarly, 6.6% (117/1768) and 5.1% (44/863) of environmental isolates, in Maipo and Maule River showed and MDR phenotype. Efforts to reduce fecal discharge into these rivers should thus focus on agriculture and urban land uses as these areas were contributing the most and more frequently to fecal contamination into the rivers, while human and cattle fecal discharges were identified as the most likely source of this fecal contamination by the MST approach. This information can be used to design better mitigation strategies, thereby reducing the burden of waterborne diseases and AMR in Central Chile.

Study on the Water Quality Characteristics of the Baoan Lake Basin in China under Different Land Use and Landscape Pattern Distributions

Land use and landscape pattern highly affect water quality. Their relationship can assist in land-use management and improve land-use efficiency. In this study, a water quality survey of rivers and lakes was performed in 2020 to analyze the effects of land use and the landscape pattern on the water quality of the rivers and lakes in the Baoan Lake basin and is expected to provide a reference for land use planning. The results demonstrated that the effects of land use on water quality were generally higher during the dry season than during the wet season; however, the opposite was demonstrated for the landscape pattern index. Cropland and urban land were closely correlated with deteriorating water quality, with contributions to total nitrogen, total phosphorous, and ammonia nitrogen in the basin. The impact of the landscape pattern of the basin on water quality was controlled by the original land-use type. In addition, the landscape configuration formed different land-use types to produce different effects on water quality. The basin scale better explained the changes in water quality, especially for construction land, followed by the 250 m and 500 m scales in the buffer zone.

Quantitative Assessment of Climatic and Reservoir-Induced Effects on River Water Temperature Using Bayesian Network-Based Approach

River flow regulations and thermal regimes have been altered by human-induced interventions (such as dam construction) or climate change (such as air temperature variations). It is of great significance to adopt a well-performed data-driven model to accurately quantify the impact of human-induced interventions or climate change over river water temperature (WT), which can help understand the underlying evolution mechanism of the river thermal regimes by dam operation or climate change. This research applied the Bayesian network-based model (BNM), which can easily identify inherently stronger associated variables with a target variable from multiple influencing variables to predict the daily WT and make a quantitative assessment of the effect produced by Three Gorges Reservoir (TGR) construction in the Yangtze River, China. A comparative study between the proposed model and two other models was implemented to verify the predicted accuracy of the BNM. With the help of the BNM model, the impact of reservoir impoundment over water temperature was quantitatively analyzed by calculating the difference between reconstructed water temperature series and observed series during the post-TGR period. The construction of the TGR posed more impact on variations in WT than the impact induced by the climate change according to results. The effect of TGR on WT can be concluded as follows: WT from October to January in post-TGR showed a remarkable warming tendency and an increase in released warmer water volumes than before, while WT showed a cooling tendency during March to June because of the hysteretic effect of WT response to increasing air temperature. The proposed BNM model shows great potential for WT prediction and ecological risk management of rivers.

Biogeochemical impacts of sewage effluents in predominantly rural river catchments: Are point source inputs distinct to background diffuse pollution?

Discharge of treated sewage effluent to rivers can degrade aquatic ecosystem quality, interacting with multiple stressors in the wider catchment. In predominantly rural catchments, the river reach influence of point source effluents is unknown relative to complex background pressures. We examined water column, sediment and biofilm biogeochemical water quality parameters along river transects (200 m upstream to 1 km downstream) during summer at five wastewater treatment works (WWTW) in Scotland. Treated sewage effluent (subset, n = 3) pollutant concentrations varied between sites. Downstream concentration profiles of water and sediment biogeochemical parameters showed complex spatial changes. A hypothesised point source signature of elevated concentrations of pollution immediately downstream of WWTW then a decaying pollution 'plume' did not commonly occur. Instead, elevated soluble reactive phosphorus (SRP), ammonium and coliforms (maximum 0.23 mgP/l, 0.33 mgN/l and >2 × 106 MPN/100 ml) occurred immediately downstream of two WWTW, whereas some downstream pollutant concentrations decreased. Microbial substrate respiration responses only differed 1 km downstream. Significantly greater concentrations of sediment metal occurred >500 m downstream, likely due to the redeposition of historic contaminated sediments. Significantly lowered chlorophyll-a downstream of one WWTW coincided with elevated metals, despite water SRP and sediment P increases. Overall, stress caused to microbes and algae by effluent contaminants outweighed the subsidy effect of WWTW nutrients. We observed variable effluent flows to the rivers limited localised pollution downstream of WWTW and overall influence of arable land cover on river water quality. Together, this challenges views of consistently discharging point sources impacting low dilution sensitive rivers in summer contrasting with 'diffuse' sources. Thus, river water column and benthic compartments are altered at varying scales by point source effluents in combination with rural catchment pollution sources, both discrete (e.g. farmyards and septic tanks) and diffuse.

Identification and Apportionment of Potential Pollution Sources Using Multivariate Statistical Techniques and APCS-MLR Model to Assess Surface Water Quality in Imjin River Watershed, South Korea

Reliable water quality monitoring data, identifying potential pollution sources, and quantifying the corresponding potential pollution source apportionment are essential for future water resource management and pollution control. Here, we collected water quality data from seven monitoring sites to identify spatiotemporal changes in surface water in the Imjin River Watershed (IRW), South Korea, distinguish potential pollution sources, and quantify the source apportionment from 2018–2020. An analysis was performed based on multivariate statistical techniques (MST) and the absolute principal component score-multiple linear regression (APCS-MLR) model. Statistically significant groups were created based on spatiotemporally similar physicochemical water quality characteristics and anthropogenic activities: low-pollution (LP) and high-pollution (HP) regions, and dry season (DS) and wet season (WS). There were statistically significant mean differences in water quality parameters between spatial clusters, rather than between temporal clusters. We identified four and three potential factors that could explain 80.75% and 71.99% in the LP and HP regions, respectively. Identification and quantitative evaluation of potential pollution sources using MST and the APCS-MLR model for the IRW may be useful for policymakers to improve the water quality of target watersheds and establish future management policies.

Evaluating the risks of spatial and temporal changes in nonpoint source pollution in a Chinese river basin

In watershed management, it is of great importance to evaluate the risks of nonpoint source (NPS) pollution. In this study, the Nonpoint Source Pollution Risk Index (NSPRI), a multi-factor NPS risk assessment model that was based on the source-sink landscape theory, was proposed and applied in Muzhuhe River Basin, Shandong, China to (1) highlight spatial and temporal variations in the risks from nitrogen and phosphorus losses, and (2) identify how the basin characteristics influenced the risk of nutrient loss. According to the analysis on land use change, the study area is featured with high proportions of forest and agricultural land uses; the area of urban and industrial land had increased considerably from 2000 and 2018. Based on the division of the calculated risk indices on subbasin scale, the area with extremely high risks has decreased from 56,442 ha to 43,922 ha. The average and coefficient of variation (CV) values of NSPRI in the river basin have dropped from 1.3 to 1.1, and from 78.2% to 48.9%, respectively. The distribution of NSPRI suggested an increase in spatial clustering and improvements in the ecological balance. Correlation analysis of the Soil and Water Assessment Tool (SWAT) model (R² > 0.68, ENS > 0.59) and NSPRI indicated the applicability of the method used (r > 0.84, p < 0.01). Analysis on the impact of metrics of land use composition, landscape, and environmental settings on NSPRI indicated that the water quality was more significantly correlated with land use composition, landscape pattern and vegetation cover than with flow path distance, soil erodibility, and rainfall erosivity. Moreover, results of redundancy analysis revealed that nutrient loss risk was better explained by land use compositions than by landscape configuration. The assessment method provided scientific support for NPS pollution control from the perspective of source-sink landscape theory.

Hierarchical systems integration for coordinated urban-rural water quality management at a catchment scale

Managing river quality is important for sustainable catchment development. In this study, we present how catchment management strategies benefit from a coordinated implementation of measures that are based on understanding key drivers of pollution. We develop a modelling approach that integrates environmental impacts, human activities, and management measures as three hierarchical levels. We present a catchment water management model (CatchWat) that achieves all three hierarchical levels and is applied to the Cherwell Catchment, UK. CatchWat simulations are evaluated against observed river flow and pollutant data including suspended solids, total nitrogen, and total phosphorus. We compare three competing hypotheses, or framings, of the catchment representation (integrated, urban-only, and rural-only framings) to test the impacts of model boundaries on river water quality modelling. Scenarios are formulated to simulate separate, combined and coordinated implementation of fertiliser application reduction and enhanced wastewater treatment. Results show that models must represent both urban and rural pollution emissions to accurately estimate river quality. Agricultural activities are found to drive river quality in wet periods because runoff is the main pathway for rural pollutants. Meanwhile, urban activities are the key source of pollution in dry periods because effluent constitutes a larger percentage of river flow during this time. Based on this understanding, we identify a coordinated management strategy that implements fertiliser reduction measures to improve river quality during wet periods and enhanced wastewater treatment to improve river quality during dry periods. The coordinated strategy performs comparably to the combined strategy but with higher overall efficiency. This study emphasises the importance of systems boundaries in integrated water quality modelling and simulating the mechanisms of seasonal water quality behaviour. Our key recommendation is that incorporating these mechanisms is required to develop coordinated strategies for river water quality management, that can ultimately lead to more efficient and sustainable catchment management.

Water pollution characteristics of inflowing rivers under different land-use patterns in the Daye Lake basin: pollution mode and management suggestions

Land use/land cover (LULC) conditions can have a profound impact on the water quality of rivers, lakes, and other water bodies within a basin. Land use status of Daye Lake basin in 2019 has been shown by Landsat 8 OLI image, water quality of Daye Lake, and 12 inflowing rivers have been investigated once a month; this study provides a comprehensive analysis of the water pollution characteristics of the inflowing rivers and lake in the basin under different LULC patterns, and providing a reference for the scientific planning of land-use types in the basin and land use research in lake basins in subtropical areas. Pollutants are mainly introduced to Daye Lake from the west (such as Da Gang) and north (such as Linjiaju Gang), with concentrations gradually decreasing within the lake from west to east. Construction land is closely associated with the total nitrogen (TN), total phosphorus (TP), permanganate index (COD_Mn), and ammonia nitrogen (NH₃-N) inputs to the basin, which can be trapped by vegetation. Agricultural dryland can contribute acid and dissolved oxygen (DO) to water. Precipitation can influence the input of pollutants, with a stronger effect on TN and weaker effect on TP. Pollutants accumulate from the inlets to the centre of the lake, with longer retention times during the dry season.

Effects of Meteorological Parameters on Surface Water Loss in Burdur Lake, Turkey over 34 Years Landsat Google Earth Engine Time-Series

The current work aims to examine the effect of meteorological parameters as well as the temporal variation on the Burdur Lake surface water body areas in Turkey. The data for the surface area of Burdur Lake was collected over 34 years between 1984 and 2019 by Google Earth Engine. The seasonal variation in the water bodies area was collected using our proposed extraction method and 570 Landsat images. The reduction in the total area of the lake was observed between 206.6 km2 in 1984 to 125.5 km2 in 2019. The vegetation cover and meteorological parameters collected that affect the observed variation of surface water bodies for the same area include precipitation, evapotranspiration, albedo, radiation, and temperature. The selected meteorological variables influence the reduction in lake area directly during various seasons. Correlations showed a strong positive or negative significant relationship between the reduction and the selected meteorological variables. A factor analysis provided three components that explain 82.15% of the total variation in the data. The data provide valuable references for decision makers to develop sustainable agriculture and industrial water use policies to preserve water resources as well as cope with potential climate changes.

Spatiotemporal analysis of land use pattern and stream water quality in southern Alberta, Canada

Alberta has over 70% of total irrigated land in Canada and 13 irrigation districts are mainly located along the rivers in southern Alberta. The runoff and irrigation return flow can carry excess nutrients, pesticides, and sediments, which adversely affect the river water quality. In the present study, the comprehensive spatiotemporal analysis of land use pattern and stream water quality in southern Alberta was conducted. The water quality monitoring on the South Saskatchewan River watershed within Alberta showed that most water quality indicators did not significantly change between 2003 and 2017. Land use maps demonstrated significant urban expansion and cropland decline in the study area from 2005 to 2015, while the irrigation area increased. Correlation analysis and redundancy analysis revealed that cropland, built-up land, and native grassland were three land use types that were positively correlated with water quality indicators. Stronger correlations between nitrogen concentration and built-up land were found in dry seasons compared with wet seasons. According to the results of cluster analysis, higher water quality indicator concentrations could be observed in groups with a higher proportion of cropland and built-up land. Significant relationships between land use patterns and water quality were found in this study, which demonstrated that further investigation is needed to identify the sources of water pollutants at a smaller scale.

Spatio-seasonal variation of water quality influenced by land use and land cover in Lake Muhazi

Understanding the influence of land use/land cover (LULC) on water quality is pertinent to sustainable water management. This study aimed at assessing the spatio-seasonal variation of water quality in relation to land use types in Lake Muhazi, Rwanda. The National Sanitation Foundation Water Quality Index (NSF-WQI) was used to evaluate the anthropogenically-induced water quality changes. In addition to Principal Components Analysis (PCA), a Cluster Analysis (CA) was applied on 12-clustered sampling sites and the obtained NSF-WQI. Lastly, the Partial Least Squares Path Modelling (PLS-PM) was used to estimate the nexus between LULC, water quality parameters, and the obtained NSF-WQI. The results revealed a poor water quality status at the Mugorore and Butimba sites in the rainy season, then at Mugorore and Bwimiyange sites in the dry season. Furthermore, PCA displayed a sample dispersion based on seasonality while NSF-WQI's CA hierarchy grouped the samples corresponding to LULC types. Finally, the PLS-PM returned a strong positive correlation (+ 0.831) between LULCs and water quality parameters in the rainy season but a negative correlation coefficient (- 0.542) in the dry season, with great influences of cropland on the water quality parameters. Overall, this study concludes that the lake is seasonally influenced by anthropogenic activities, suggesting sustainable land-use management decisions, such as the establishment and safeguarding protection belts in the lake vicinity.

Catchment versus Riparian Buffers: Which Land Use Spatial Scales Have the Greatest Ability to Explain Water Quality Changes in a Typical Temperate Watershed?

Identifying the multi-scale spatial relationship between land use and water quality is critical for determining the priorities and key areas of river management. To more accurately identify the scale effect of land-use patterns on water quality and quantitatively distinguish the difference in the impacts of land-use composition and configuration on water quality, we used 94 sites to extract the upstream catchment and riparian buffer zone with different widths. The results showed that the ability of land use variables with different buffer widths to explain water quality differed slightly from the ability of these variables at the catchment scale, and the joint explanatory ability of land use composition and configuration was greater than that of each individually. The patch density and landscape shape index of cultivated land, shrubland, and built-up land in the buffer area close to the water bodies were the main factors for the increase in the concentration of total nitrogen, nitrate nitrogen, total phosphorus, and suspended solids. As the width of the buffer increased, the role of the percent of land use increased. Our research indicates that water quality management needs to adopt a multi-scale perspective and focus on key local areas while coordinating at a broader scale.

Scenario-Based Hydrological Modeling for Designing Climate-Resilient Coastal Water Resource Management Measures: Lessons from Brahmani River, Odisha, Eastern India

Widespread urban expansion around the world, combined with rapid demographic and climatic changes, has resulted in serious pollution issues in many coastal water bodies. To help formulate coastal management strategies to mitigate the impacts of these extreme changes (e.g., local land-use or climate change adaptation policies), research methodologies that incorporate participatory approaches alongside with computer simulation modeling tools have potential to be particularly effective. One such research methodology, called the “Participatory Coastal Land-Use Management” (PCLM) approach, consists of three major steps: (a) participatory approach to find key drivers responsible for the water quality deterioration, (b) scenario analysis using different computer simulation modeling tools for impact assessment, and (c) using these scientific evidences for developing adaptation and mitigation measures. In this study, we have applied PCLM approach in the Kendrapara district of India (focusing on the Brahmani River basin), a rapidly urbanizing area on the country’s east coast to evaluate current status and predict its future conditions. The participatory approach involved key informant interviews to determine key drivers of water quality degradation, which served as an input for scenario analysis and hydrological simulation in the next step. Future river water quality (BOD and Total coliform (Tot. coli) as important parameters) was simulated using the Water Evaluation and Planning (WEAP) tool, considering a different plausible future scenario (to 2050) incorporating diverse drivers and pressures (i.e., population growth, land-use change, and climate change). Water samples (collected in 2018) indicated that the Brahmani River in this district was already moderately-to-extremely polluted in comparison to the desirable water quality (Class B), and modeling results indicated that the river water quality is likely to further deteriorate by 2050 under all of the considered scenarios. Demographic changes emerged as the major driver affecting the future water quality deterioration (68% and 69% for BOD and Tot. coli respectively), whereas climate change had the lowest impact on river water quality (12% and 13% for BOD and Tot. coli respectively), although the impact was not negligible. Scientific evidence to understand the impacts of future changes can help in developing diverse plausible coastal zone management approaches for ensuring sustainable management of water resources in the region. The PCLM approach, by having active stakeholder involvement, can help in co-generation of the coastal management options followed by open access free software, and models can play a relevant cost-effective approach to enhance science-policy interface for conservation of natural resources.

Impacts of land use at multiple buffer scales on seasonal water quality in a reticular river network area

The assessment and prediction of regional water quality are fundamental inputs to environmental planning and watershed ecological management. This paper explored spatiotemporal changes in the correlation of water quality parameters (WQPs) and land-use types (LUTs) in a reticular river network area. Water samples of 44 sampling sites were collected every quarter from 2016 to 2018 and evaluated for dissolved oxygen (DO), total phosphorus (TP), ammonia nitrogen (NH₃-N), and permanganate index (COD_Mn). A redundancy analysis (RDA) and stepwise multiple linear regression (SMLR) were applied to analyze the land-use type impacts on seasonal WQPs at five buffer scales (100, 200, 500, 800, and 1000 m). The Kruskal–Wallis test results revealed significant seasonal differences in NH₃-N, TP, COD_Mn, and DO. The area percentages of farmland, water area and built-up land in the study area were 38.96%, 22.75% and16.20%, respectively, for a combined total area percentage of nearly 80%. Our study showed that orchard land had an especially favorable influence on WQPs. Land-use type impacts on WQPs were more significant during the dry season than the wet season. The total variation explained by LUTs regarding WQPs at the 1 km buffer scale was slightly stronger than at smaller buffer scales. Built-up land had a negative effect on WQPs, but orchard and forest-grassland had a positive effect on WQPs. The effects of water area and farmland on WQPs were complex on different buffer scales. These findings are helpful for improving regional water resource management and environmental planning.

Assessment of Drinking Water Sources for Water Quality, Human Health Risks, and Pollution Sources: A Case Study of the District Bajaur, Pakistan

The focus of the present study was to assess the quality of different drinking water sources, impacts of poor water quality on human health, and to apportion pollution source(s) of the district Bajaur, Pakistan. Drinking water samples (n = 331) were randomly collected from springs, hand pumps, open wells, and tube wells and analyzed for physicochemical parameters including toxic elements, and bacteriological contamination (i.e., Escherichia coli). Furthermore, a questionnaire survey was conducted to record the cases of waterborne diseases in the study area. The results showed that total suspended solids and bacteriological contamination exceeded the permissible limits of the WHO in all four of the water sources. Among the potentially toxic elements, Cd, Pb, and Mn were above the permissible limits of the WHO in some samples. The hazard index for spring water was found to exceed the toxicity level (i.e., HI > 1) set by US EPA for both adults and children, while the sources from hand pumps, open wells, and tube wells were within the safe limit. The order for the overall safety level for water quality in the study area was tube wells > open wells > hand pumps > springs. The pollution source apportionment statistics revealed that both geogenic and anthropogenic activities are the sources of drinking water contamination. The results of the questionnaire survey indicated that reports of waterborne diseases were highest in respondents who took their drinking water from springs, whereas reports of diseases were moderate in respondents taking their water from open wells and hand pumps and lowest in respondents taking their water from tube wells. Based on the findings of the study, the tube well source of water is recommended for drinking water purposes.

Water Quality Pollution Control and Watershed Management Based on Community Participation in Maros City, South Sulawesi, Indonesia

Increases in the number of urban residents have significant impacts on spatial pressure, affecting the utilization of river basins. The purpose of this study is to analyze (1) the increase in population and changes in spatial use as determinants of the complexity of the watershed ecosystem; (2) the effect of housing development, urban activity systems, and land use changes on the degradation of the environmental quality of the watershed; and (3) the direct and indirect effects of changes in spatial use, land reclamation, and community behavior on water pollution and the sustainability of watershed management in Maros City. The research method used is a sequential explanatory design combining quantitative and qualitative research methods. Data were obtained through observation, in-depth interviews, surveys, and documentation. The study findings show that land use change, complexity of spatial use, and community behavior have a negative impact on the environmental quality of the watershed. Housing development, urban activity systems, and changes in land use had a significant effect on environmental quality degradation, with a coefficient of determination of 73.9%. Furthermore, the influence of spatial use, land reclamation, and community behavior on water pollution in the watershed was 72.82%. This study may serve to assist the decision-making of and policy formation by the Maros Regency Government in the framework of controlling the use of watersheds, working towards their social, economic, and environmental sustainability.

Trophic state and limiting nutrient evaluations using trophic state/level index methods: a case study of Borçka Dam Lake

The relationships between nutrients and the trophic state of Borçka dam reservoir in the Çoruh River Basin, which is located in the Eastern Black Sea region of Turkey, were evaluated using the trophic state index (TSI), trophic level index (TLI), and statistical analysis. The samples data were analyzed for chlorophyll-a (Chl-a), total phosphorus (TP), total nitrogen (TN), and secchi disk (SD). In the evaluation, according to the TSI' TLI and Turkish legislation, the reservoir is assessed as mesotrophic in terms of TP, TN data of the water quality. The measurement results of these parameters are higher at the depth points and lower on the surface. The Chl-a parameter is evaluated mesotrophic with 2013 data at the depth, and oligotrophic with 2016 data. The result of TSI (Chl-a) < TSI (SD), TSI (Chl-a) < TSI (TP), and TSI (TN) indicate non-algal turbidity. At the same time, this was verified by calculating the non-algal turbidity coefficient (Kna). It is observed that there is a low correlation between Chl-a and Kna, however a low correlation with TN, and a high correlation with TP. Non-algal particles in the dam lake may occur due to surface runoff and soil erosion from the agricultural area and human settlements. Regression analysis was conducted to determine the relationship between nutrients and Chl-a. The relationship of Chl-a concentration with TN, TP, and TN/TP concentrations is weak. This supports that there are inorganic suspended solids (non-volatile suspended solids) with high underwater light availability.Graphical abstract.

Effects of Land Cover Changes on Sediment and Nutrient Balance in the Catchment with Cascade-Dammed Waters

It is commonly believed that changes in the use of the catchment area have a direct impact on the quality of the water environment. Rivers with dams and reservoirs are characterized by a disturbed outflow of sediments and nutrients from the catchment area. The research was based on indicating the variation in time and space of loads of selected parameters of the water quality of the Brda River (Northern Poland) against the land cover changes based on the CORINE Land Cover (CLC) data for the 1990–2018 period. In the lower part of the Brda catchment area, there are three hydropower dams with reservoirs in the form of a cascade, whose work clearly affects the hydrological regime of the river. The analysis of the dependence of the dynamics of water quality changes on the usage of CLC was based on indicators such as sediments (suspended sediment load) and nutrients (total phosphorus load and total nitrogen load). The use of hydrological data on the Brda discharge above and below the reservoirs made it possible to calculate sediment and nutrient trapping efficiency. Linking the CLC data with the indices responsible for the mechanical denudation of the catchment area made it possible to show the strength of changes taking place in the catchment area. The results of the research do not indicate any direct correlation between land cover changes and the dynamics of the denudation process and matter transport in the Brda catchment area. As our research shows, the strong influence on the hydrological regime of the catchment points out the necessity to search for still other research methods supporting the decision-making cycle in the field of water management in the face of climate change.

Water quality impacts of urban and non-urban arid-land runoff on the Rio Grande

Urban surface runoff from storms impacts the water quality dynamics of downstream ecosystems. While these effects are well-documented in mesic regions, they are not well constrained for arid watersheds, which sustain longer dry periods, receive intense but short-lived storms, and where stormwater drainage networks are generally isolated from sewage systems. We used a network of high-frequency in situ water quality sensors located along the Middle Rio Grande to determine surface runoff origins during storms and track rapid changes in physical, chemical, and biological components of water quality. Specific conductivity (SpCond) patterns were a reliable indicator of source, distinguishing between runoff events originating primarily in urban (SpCond sags) or non-urban (SpCond spikes) catchments. Urban events were characterized by high fluorescent dissolved organic matter (fDOM), low dissolved oxygen (including short-lived hypoxia <2 mg/L), smaller increases in turbidity and varied pH response. In contrast, non-urban events showed large turbidity spikes, smaller dissolved oxygen sags, and consistent pH sags. Principal component analysis distinguished urban and non-urban events by dividing physical and biogeochemical water quality parameters, and modeling of DO along the same reach demonstrated consistently higher oxygen demand for an urban event compared to a non-urban event. Based on our analysis, urban runoff poses more potential ecological harm, while non-urban runoff poses a larger problem for drinking water treatment. The comparison of our results to other reports of urban stormwater quality suggest that water quality responses to storm events in urban landscapes are consistent across a range of regional climates.

Climatic seasonality and water quality in watersheds: a study case in Limoeiro River watershed in the western region of São Paulo State, Brazil

Applying the climatological water balance (WB) concept to describe the relationship between climatic seasonality and surface water quality according to different forms of land use and land cover (LULC) is an important issue, but little explored in the literature. In this paper, we evaluate the influence of WB on surface water quality and its impacts when interacting with LULC. We monitored 11 sampling points during the four seasons of the year, from which we estimate WQI (water quality index) and TSI (trophic state index). We found an effect of the seasonality factor on both WQI values (F(3,30) = 12.472; p < 0.01) and in TSI values (F(3,30) = 6.967; p < 0.01). We noticed that LULC interferes in the way that the water balance influences the WQI and TSI values since in sampling points closest to higher urban density, with little or no riparian protection, the correlation between water balance and water quality was lower. In the stations that had the lowest water surplus and deficit, there was positive linearity between water balance and WQI. However, in the seasons when the surplus and water deficit recorded were extreme, there was no linearity. We conclude that water deficiency impairs the quality of surface water. In the extreme surplus water season, the homogeneity of WQI samples was lower, suggesting a higher interaction between rainwater and LULC. This study contributes to design management strategies of water resources, considering the climatic seasonality for optimization.

Effects of Land Use on Stream Water Quality in the Rapidly Urbanized Areas: A Multiscale Analysis

The land use and land cover changes in rapidly urbanized regions is one of the main causes of water quality deterioration. However, due to the heterogeneity of urban land use patterns and spatial scale effects, a clear understanding of the relationships between land use and water quality remains elusive. The primary purpose of this study is to investigate the effects of land use on water quality across multi scales in a rapidly urbanized region in Hangzhou City, China. The results showed that the response characteristics of stream water quality to land use were spatial scale-dependent. The total nitrogen (TN) was more closely related with land use at the circular buffer scale, whilst stronger correlations could be found between land use and algae biomass at the riparian buffer scales. Under the circular buffer scale, the forest and urban greenspace were more influential to the TN at small buffer scales, whilst significant positive or negative correlations could be found between the TN and the areas of industrial land or the wetland and river as the buffer scales increased. The redundancy analysis (RDA) showed that more than 40% variations in water quality could be explained by the landscape metrics at all circular and riparian buffer scales, and this suggests that land use pattern was an important factor influencing water quality. The variation in water quality explained by landscape metrics increased with the increase of buffer size, and this implies that land use pattern could have a closer correlation with water quality at larger spatial scales.

Advancing Understanding of Land Use and Physicochemical Impacts on Fecal Contamination in Mixed-Land-Use Watersheds

Understanding mixed-land-use practices and physicochemical influences on Escherichia (E.) coli concentrations is necessary to improve water quality management and human health. Weekly stream water samples and physicochemical data were collected from 22 stream gauging sites representing varying land use practices in a contemporary Appalachian watershed of the eastern USA. Over the period of one annual year, Escherichia (E.) coli colony forming units (CFU) per 100 mL were compared to physicochemical parameters and land use practices. Annual average E. coli concentration increased by approximately 112% from acid mine drainage (AMD) impacted headwaters to the lower reaches of the watershed (approximate averages of 177 CFU per 100 mL vs. 376 CFU per 100 mL, respectively). Significant Spearman’s correlations (p < 0.05) were identified from analyses of pH and E. coli concentration data representing 77% of sample sites; thus highlighting legacy effects of historic mining (AMD) on microbial water quality. A tipping point of 25–30% mixed development was identified as leading to significant (p < 0.05) negative correlations between chloride and E. coli concentrations. Study results advance understanding of land use and physicochemical impacts on fecal contamination in mixed-land-use watersheds, aiding in the implementation of effective water quality management practices and policies.

Emission and fate of antibiotics in the Dongjiang River Basin, China: Implication for antibiotic resistance risk

Antibiotics used for human and veterinary purposes are released into the environment, resulting in potential adverse effects, including the development and spread of antibiotic resistant bacteria. Here we investigated the dynamic fate of 36 antibiotics in a large river basin Dongjiang in South China, and discussed their potential antibiotic resistance selection risk. Based on the usage, excretion rate, wastewater treatment rate, human population and animal numbers the emissions of 36 frequently detected antibiotics were estimated for the Dongjiang River Basin. The total usage of the 36 antibiotics in the basin was 623.4 tons, which included 37% for human use and the rest for veterinary purposes. After being metabolized and partially treated, the amount of antibiotics excreted and released into the environment decreased to 267.6 tons. By allocating the high-precision antibiotic discharge inventory to 42 sewage plants and 17 livestock farms, an improved GREAT-ER (Geography referenced Regional Exposure Assessment Tool for European Rivers) model for the Dongjiang River Basin, with a well calibration river flow network based on the SWAT (Soil and Water Assessment Tool), was established to simulate the dynamic fate of 36 antibiotics. The simulation results showed that antibiotics contaminated >50% of the river sections. The modelled concentrations in water were almost within an order of magnitude of the measured concentrations. Antibiotic contamination in the dry season was obviously higher than that in the wet season. The concentrations of the antibiotics were always higher at the discharge zones and lower reaches of the river basin than the other reaches. The antibiotic resistance risk assessment showed that 23 out of the 36 antibiotics (nearly 65%) could pose high risks in the river basin. For those river reaches with high risks, the risk levels could mostly be reduced to low risk levels with a certain distance (15 km) from the pollution source. Therefore, more attention should be paid to those impact zones in term of antibiotic resistance.

Surface Water Quality Analysis Using CORINE Data: An Application to Assess Reservoirs in Poland

Reservoirs are formed through the artificial damming of a river valley. Reservoirs, among others, capture polluted load transported by the tributaries in the form of suspended and dissolved sediments and substances. Therefore, reservoirs are treated in the European Union (EU) as “artificial” or “heavily modified” surface water bodies. The reservoirs’ pollutant load depends to a large extent on the degree of anthropogenic impact in the respective river catchment area. The purpose of this paper is to assess the mutual relation between the catchment area and the reservoirs. In particular, we focus on the effects of certain land use/land cover on reservoirs’ water quality. For this study, we selected twenty Polish reservoirs for an in-depth analysis using 2018 CORINE Land Cover data. This analysis allowed the identification of the main triggering factors in terms of water quality of the respective reservoirs. Moreover, our assessment clearly shows that water quality of the analysed dam reservoirs is directly affected by the composition of land use/land cover, both of the entire total reservoir catchment areas and the directly into the reservoir draining sub-catchment areas.

Spatially Varying and Scale-Dependent Relationships of Land Use Types with Stream Water Quality

Understanding the complex relationships between land use and stream water quality is critical for water pollution control and watershed management. This study aimed to investigate the relationship between land use types and water quality indicators at multiple spatial scales, namely, the watershed and riparian scales, using the ordinary least squares (OLS) and geographically weighted regression (GWR) models. GWR extended traditional regression models, such as OLS to address the spatial variations among variables. Our results indicated that the water quality indicators were significantly affected by agricultural and forested areas at both scales. We found that extensive agricultural land use had negative effects on water quality indicators, whereas, forested areas had positive effects on these indicators. The results also indicated that the watershed scale is effective for management and regulation of watershed land use, as the predictive power of the models is much greater at the watershed scale. The maps of estimated local parameters and local R² in GWR models showcased the spatially varying relationships and indicated that the effects of land use on water quality varied over space. The results of this study reinforced the importance of watershed management in the planning, restoration, and management of stream water quality. It is also suggested that planners and managers may need to adopt different strategies, considering watershed characteristics—such as topographic features and meteorological conditions—and the source of pollutants, in managing stream water quality.

Influences of Land-Use Dynamics and Surface Water Systems Interactions on Water-Related Infectious Diseases—A Systematic Review

Human interactions with surface water systems, through land-use dynamics, can influence the transmission of infectious water-related diseases. As a result, the aim of our study was to explore and examine the state of scientific evidence on the influences of these interactions on water-related infectious disease outcomes from a global perspective. A systematic review was conducted, using 54 peer-reviewed research articles published between 1995 and August 2019. The study revealed that there has been an increase in the number of publications since 2009; however, few of these publications (n = 6) made explicit linkages to the topic. It was found that urban and agricultural land-use changes had relatively high adverse impacts on water quality, due to high concentrations of fecal matter, heavy metals, and nutrients in surface water systems. Water systems were found as the common “vehicle” for infectious disease transmission, which in turn had linkages to sanitation and hygiene conditions. The study found explicit linkages between human–surface water interaction patterns and the transmission of water-based disease. However, weak and complex linkages were found between land-use change and the transmission of water-borne disease, due to multiple pathways and the dynamics of the other determinants of the disease. Therefore, further research studies, using interdisciplinary and transdisciplinary approaches to investigate and enhance a deeper understanding of these complexities and linkages among land use, surface water quality, and water-related infectious diseases, is crucial in developing integrated measures for sustainable water quality monitoring and diseases prevention.

Evidence and impact of map error on land use and land cover dynamics in Ashi River watershed using intensity analysis

Previously, applications of intensity analysis (IA) on land use and land cover change (LULCC) studies have focused on deviations from uniform intensity (UI) and failed to quantify the reasons behind these deviations. This study presents the application of IA with hypothetical errors that could explain non-uniform LULCC in the context of IA at four-time points. LULCC in the Ashi watershed was examined using Landsat images from 1990, 2000, 2010 and 2014 showing the classes: Urban, water, agriculture, close canopy, open canopy and other vegetation. Matrices were created to statistically examine LULCC using IA. The results reveal that the seeming LULCC intensities are not uniform with respect to the interval, category and transition levels of IA. Error analysis indicates that, hypothetical errors in 13%, 19% and 11.2% of the 2000, 2010 and 2014 maps respectively could account for all differences between the observed gain intensities and the UI; while errors in 12%, 21%, and 11% of the 1990, 2000 and 2010 maps respectively could account for all differences between the observed loss intensities and the UI. A hypothetical error in 0.6% and 1.6% of the 1990 map; 1.5% and 4% of the 2000 map; 1.2% and 2.1% of the 2010 map could explain divergences from uniform transitions given URB gain and AGR gain during 1990-2000, 2000-2010 and 2010-2014 respectively. Evidence for a specific deviation from the relevant hypothesized UI is either strong or weak depending on the size of these errors. We recommend that users of IA concept consider assessing their map errors, since limited ground information on past time point data exist. These errors will indicate strength of evidence for deviations and reveals patterns that increase researcher's insight on LULCC processes.

Effect of Hyporheic Exchange on Macroinvertebrate Community in the Weihe River Basin, China

The effect of hyporheic exchange on macroinvertebrates is a significant topic in ecohydraulics. A field study was conducted during May and June 2017 to investigate the impacts of magnitude and patterns of hyporheic exchange on the sediment macroinvertebrate community in the Weihe River basin. The results demonstrate that upwelling flows cause resuspension of riverbed sediment, increasing the proportion of swimmer groups (such as Baetidae) in the macroinvertebrate community. However, large resuspension of river bed sediment results in a reduced abundance of macroinvertebrates. By controlling the transport processes of dissolved oxygen (DO), dissolved organic carbon (DOC), nutrients, temperature, and different patterns of hyporheic exchange strongly influence the structure of macroinvertebrate communities. Downwelling is more likely to produce rich invertebrate communities than upwelling. The magnitude for the hyporheic flux of 150–200 mm/d was optimal for the macroinvertebrate community in the Weihe River Basin. Above or below this rate results in a decline in community abundance and diversity. We suggest that research is conducted to better understand the effects of hyporheic exchange across bedforms on macroinvertebrate communities. The study supports any activities to preserve the ecological functions and health of rivers dominated by fine-grained sediments.

Impacts of Landscapes on Water Quality in A Typical Headwater Catchment, Southeastern China

The relationship between land landscape and water quality has been a hot topic, especially for researchers in headwater catchment, because of drinking water safety and ecological protection. In this study, Lita Watershed, a typical headwater catchment of Southeast China, was selected as the study area. During 2015 and 2016, water samples were collected from 18 sampling points every month, and 19 water quality parameters were tested such as nutrients and heavy metals. Through multistatistics analysis, the results show that the most sensitive water quality parameters are Cr, NO3, NO2, and COD. The type and scale of water body have direct effects on water quality, while the land-use patterns in the surrounding areas have an indirect impact on the concentration and migration of pollutants. This effect is sensitive to seasonal change because heavy metals are mainly from atmospheric deposition, but nutrients are mainly from agricultural nonpoint source pollution. According to the results, increasing the proportion of forest land and paddy field is effective to the reduction of water nutrients. Besides, balancing the configuration of water bodies, especially increasing the capacity of the pond, can significantly alleviate the water pollution in the dry season. This study is useful to provide policy suggestion for refined watershed management and water source planning basing on seasons and pollution sources.

New ecological dam for sediment and overlying water pollution treatment based on microbial fuel cell principle

In this study, a new ecological dam based on the microbial fuel cell principle (MFCED) was designed to remove pollutants from river sediments and water bodies. Sediment organics were better removed in the MFCED mode in comparison with the other two modes (ecological dam with open circuit (OCED) and ecological dam filled with gravel in cathode chamber (GMFCED)). The difference of nitrogen source in water had little effect on the removal of chemical oxygen demand (COD) (70-80%), while nitrate was more readily removed in the MFCED. The voltage curve and power curve were measured to understand the bioelectricity generation of MFCED. During the stable operation phase of MFCED, the voltage was stabilized between 0.09-0.15 V. The results of high-throughput sequencing indicated that the anode and cathode diversities of MFCED were more than the other systems, and the species diversity of the anode was more than that of the cathode in the MFCED. Graphical abstract.

Integrated Urban Water Management and Water Security: A Comparison of Singapore and Hong Kong

Integrated Urban Water Management (IUWM) has emerged in the past two decades as a promising approach to the application of Integrated Water Resources Management (IWRM) principles at the city-level. IUWM is expected to contribute to the achievement of multiple policy objectives, often including increased water security. This paper uses a case-based approach to study the impact of IUWM on water security, focusing on the influence of the level of institutionalization of IUWM within water governance at the city-level. Process tracing is applied to the cases of Singapore and Hong Kong, in which IUWM has been adopted but implementation and outcomes have diverged. We find that the depth of institutionalization, a difference between the two cases identified at the outset, has contributed to the achievement of better water security outcomes in Singapore as it has facilitated the development and implementation of a more far-reaching strategy. A supportive governance framework appears to amplify the impact of IUWM on progress towards water security and other policy targets.

Effect of Land Use Changes on Water Quality in an Ephemeral Coastal Plain: Khambhat City, Gujarat, India

Rapid changes in land use and land cover pattern have exerted an irreversible change on different natural resources, and water resources in particular, throughout the world. Khambhat City, located in the Western coastal plain of India, is witnessing a rapid expansion of human settlements, as well as agricultural and industrial activities. This development has led to a massive increase in groundwater use (the only source of potable water in the area), brought about significant changes to land management practices (e.g., increased fertilizer use), and resulted in much greater amounts of household and industrial waste. To better understand the impacts of this development on the local groundwater, this study investigated the relationship between groundwater quality change and land use change over the 2001–2011 period; a time during which rapid development occurred. Water quality measurements from 66 groundwater sampling wells were analyzed for the years 2001 and 2011, and two water quality indicators (NO3− and Cl− concentration) were mapped and correlated against the changes in land use. Our results indicated that the groundwater quality has deteriorated, with both nitrate (NO3−) and chloride (Cl−) levels being elevated significantly. Contour maps of NO3− and Cl− were compared with the land use maps for 2001 and 2011, respectively, to identify the impact of land use changes on water quality. Zonal statistics suggested that conversion from barren land to agricultural land had the most significant negative impact on water quality, demonstrating a positive correlation with accelerated levels of both NO3− and Cl−. The amount of influence of the different land use categories on NO3− increase was, in order, agriculture > bare land > lake > marshland > built-up > river. Whereas, for higher concentration of Cl− in the groundwater, the order of influence of the different land use categories was marshland > built-up > agriculture > bare land > lake > river. This study will help policy planners and decision makers to understand the trend of groundwater development and hence to take timely mitigation measures for its sustainable management.

Influence of land use on trophic state indexes in northeast Brazilian river basins

Eutrophication is a natural process within the ecological succession of aquatic ecosystems that results from nutrient inputs to water bodies, especially limiting elements such as phosphorus and nitrogen. However, the anthropogenic activities in river basin influence areas accelerate the eutrophication process of water bodies. Eutrophication is a global problem and considered one of the most relevant reasons of aquatic environments' degradation. In this context, watercourses that make up the Eastern Water Planning and Management Region (RPGA) receive high pollutant contributions due to release of wastewater and agriculture diffuse sources from cities located in influence area. The present study aims to evaluate the land use effect in trophic state of the water bodies in Eastern RPGA basins. The Carlson Trophic State Index in 1977, adjusted by Lamparelli 2004, was used to determine the eutrophication degree of the three river basins (Almada, Cachoeira, and Una) located in the Eastern RPGA. The nutrient and chlorophyll a data were obtained from the Monitoring Program (Monitora) of Environment and Water Resources Institute of Bahia (INEMA), covering the period from 2008 to 2015, at thirteen (13) sampling sites, with quarterly collections. The results showed that, among three basins analyzed, Cachoeira River basin presented the worst values for trophic state index (TSI) due to the high level of anthropization, while best results were found in Una basin. It was verified that land use exerted a significant influence on the water quality of bodies of water evaluated.

Effect of watershed land use on tributaries' water quality in the east African Highland

A study was carried out on four tributaries of Gilgel Gibe Reservoir to identify water physicochemical characteristics in different land use categories (farmland, naturally vegetated land, and settlement). Water samples were collected from 12 sampling sites along four permanent streams flowing into Gilgel Gibe Reservoir. Data sets were evaluated using nonparametric statistical techniques. Dissolved oxygen (DO), temperature, biochemical oxygen demand (BOD₅), total phosphorus (TP), soluble reactive phosphorus (SRP), total nitrogen (TN), turbidity, total dissolved solids (TDS), and total suspended solids (TSS) spatially showed significant differences in the wet season and DO, temperature, and BOD₅ varied significantly during the dry season. When excluding DO, electrical conductivity (EC), and TP during the wet and dry seasons, the remaining variables showed significant differences. During the wet season, concentrations of most water quality parameters were greatest in influents from agricultural land. Pollution and eutrophication risk is closely associated with drainage from agricultural land, requiring that emphasis and priorities be given to land use management and conservation.

Impact of Changes of Land Use on Water Quality, from Tropical Forest to Anthropogenic Occupation: A Multivariate Approach

Worldwide, it is acknowledged that changes of land use influence water quality; however, in tropical forests, the relationship between land use and water quality is still poorly understood. This study assessed spatial and seasonal variations in water quality, and the relationship between water quality and changes of land use in the Bobos-Nautla River, whose upper course runs across a patch of a tropical cloud forest. Spatial and seasonal variations in water quality and land use were assessed with multivariate tools. A cluster analysis, as well as a Principal Component Analysis (PCA-3D), identified three groups of sites: (1) an upper portion, which showed the best water quality and the broadest natural vegetation coverage; (2) a middle course, with high nitrogen and phosphorus concentrations associated with extensive agricultural uses; and (3) a lower course, characterized by the highest levels of total and fecal coliforms, as well as ammonia nitrogen, associated with the highest percentage of urbanization and human settlements. Our findings demonstrate the impact of changes of land use on water quality of rivers running through cloud forests in tropical zones, which are currently endangered ecosystems.