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Soil erosion is one of the most common types of land degradation. To provide useful information for proper management, quantitative soil erosion evaluation and identification of effective factors are needed. However, rare studies have been reported on spatial modeling of soil erosion in connection with affective factors to prioritize the locality and the type of erosion control measures Hence, the aim of this study was to (1) assess erosion-prone areas in the Talar Watershed, Iran, using the Revised Universal Soil Loss Equation (RUSLE) model, and (2) investigate the relationship between soil erosion variability and land-use changes. Toward that, the ordinary least squares (OLS), geographically weighted regression (GWR) models, and Principal Component Analysis (PCA) were used to analyze spatial relationships between soil erosion, and land-use, and the RUSLE factors. The results of the OLS and GWR models indicated these relationships are spatially non-stationary and GWR models had a good predictive performance rather than OLS with lower Akaike's Information Criterion (from 254.31 to 276.81 in OLS, and from 247.87 to 269.42 in GWR) and higher adjusted R2 values (from 0.12 to 0.54 in OLS, and from 0.36 to 0.66 in GWR). Among the aforementioned variables, LS factor, P factor, forest, and irrigated land were the most effective variables in GWR models. The results of PCA showed PC1 and PC2 explained 66.2 % of the variation in soil erosion concerning land-use and the RUSLE factors. These results provided appropriate references for managers and experts in the proper planning of the study watershed.

Ephemeral gullies are widely distributed in the hilly and gully region of the Loess Plateau and play a unique role in the slope gully erosion system. Rapid and accurate identification of ephemeral gullies impacts the distribution law and development trend of soil erosion on the Loess Plateau. Deep learning algorithms can quickly and accurately process large data samples that recognize ephemeral gullies from remote sensing images. Here, we investigated ephemeral gullies in the Zhoutungou watershed in the hilly and gully region of the Loess Plateau in China using satellite and unmanned aerial vehicle images and combined a deep learning image semantic segmentation model to realize automatic recognition and feature extraction. Using Accuracy, Precision, Recall, F1value, and AUC, we compared the ephemeral gully recognition results and accuracy evaluation of U-Net, R2U-Net, and SegNet image semantic segmentation models. The SegNet model was ranked first, followed by the R2U-Net and U-Net models, for ephemeral gully recognition in the hilly and gully region of the Loess Plateau. The ephemeral gully length and width between predicted and measured values had RMSE values of 6.78 m and 0.50 m, respectively, indicating that the model has an excellent recognition effect. This study identified a fast and accurate method for ephemeral gully recognition in the hilly and gully region of the Loess Plateau based on remote sensing images to provide an academic reference and practical guidance for soil erosion monitoring and slope and gully management in the Loess Plateau region.

Landscape and quality attributes are major ecosystem characteristics closely associated with soil conservation service (SCS). However, the intrinsic mechanisms by which these two attributes influence SCS are still unclear. Therefore, this study quantitatively analyzed the landscape pattern, ecological quality, and SCS in the Lianshui River watershed (a typical soil and water loss area of red soil in southern China) and its sub-watersheds in 2019. The boosted regression tree model was used to explore the influence of 15 factors (i.e., landscape and quality attributes) on SCS at the sub-watershed scale. According to the results, compared with the landscape attribute, the quality attribute of the watershed ecosystem could better explain the spatial heterogeneity of SCS across 66 sub-watersheds. The overall degree of influence of five quality factors on SCS reached 57.81%, with the highest being the normalized differential build-up and bare soil index (NDBSI), at 25.11%. Among 10 landscape factors, aggregation had the greatest influence on SCS, at 28.64%. The relationships between key influencing factors and SCS were non-monotonic and non-linear, with threshold effects. For example, NDBSI values of 0.18–0.41 had a positive influence on SCS, while NDBSI values of 0.41–0.65 had a negative influence on SCS. The findings broaden our understanding of the response of SCS to changes in landscape and quality attributes at the sub-watershed scale, and could offer comprehensive support for soil erosion management in the watershed ecosystem.

Funding Information: We thank the organizers and funders of the ILTER Nitrogen Initiative Training Course and Workshop in Hokkaido, Japan in June 2016, which brought together many of the participants in this project. Templer was supported by a US National Science Foundation LTER grant NSF DEB 1637685. McDowell was supported by US National Science Foundation LTER grant NSF DEB 1831592. We are grateful to the EU Horizon 2020 funded eLTER PLUS project (Grand Agreement No. 871128) for financial support to Haase and Dirnböck. Dirnböck was also funded by the LTER-CWN project (FFG project number 858024). This study was partly supported by the Research Initiative Grants of the ILTER, Grants-in-Aid for Scientific Research (17H03833), and Research Institute for Humanity and Nature (RIHN; a constituent member of NIHU) Project No. 14200156. Sharif was supported by NRT-INFEWS: UMD Global STEWARDS (STEM Training at the Nexus of Energy, WAter Reuse and FooD Systems) that was awarded to the University of Maryland School of Public Health by the National Science Foundation National Research Traineeship Program, Grant number 1828910. The monitoring of the Svartberget site in Sweden was funded by the SITES program from the Swedish Research Council. The monitoring of the Volbu Nyhaga site in Norway was part of JOVA—The Norwegian Agricultural Environmental Monitoring Programme, financed by the Ministry of Agriculture and Food. Lajtha was supported by NSF grants DEB-1257032 and DEB-1440409 to the H. J. Andrews Long Term Ecological Research program. The data collection in the Wüstebach catchment was supported by TERENO (Terrestrial Environmental Observatories) funded by the Helmholtz-Gemeinschaft. We thank the “Hessisches Landesamt für Naturschutz, Umwelt und Geologie” for providing data from the Rhine-Main-Observatory. I.Kokorīte was supported by the University of Latvia grant No. AAp2016/B041//Zd2016/AZ03. We thank the Latvian Environment, Geology and Meteorology Center for providing the monitoring data for Latvian site. Anna Avila was supported by Spanish Ministry of Science projects CGL2017-84687-C2-2-R and CGL2009-13188-C03-01. We thank the Tyrolean Alps Long-Term Sociological Ecological and Research (LTSER, Austria) and R. Psenner and S. Morales for helping with data for Piburger See. Data from Hubbard Brook were supported by the National Science Foundation (DEB-1907683) and US Forest Service, Northern Research Station. A. Robison was supported by US National Science Foundation LTER grant NSF OCE 1637630. W. Dodds was supported by NSF DEB 2025849. Observations at Lange Bramke site were funded by the Ministry of Nutrition, Agriculture and Consumer Protection of Lower Saxony under the Permanent Soil Monitoring Programme. The Krofdorf site was funded by the Hessian Ministry of Environment, Climate Protection, Agriculture and Consumer Protection under the “Waldökosystemstudie Hessen”. SRM Lins was supported by the São Paulo Research Foundation—FAPESP, grant number 2012/20377-9. Long-term monitoring at Lake Maggiore (LTER site EU-IT08-001-A) was funded by the International Commission for the Protection of Swiss-Italian waters (CIPAIS). We thank Emma Conrad-Rooney for help with Fig. . Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG. Previous studies have evaluated how changes in atmospheric nitrogen (N) inputs and climate affect stream N concentrations and fluxes, but none have synthesized data from sites around the globe. We identified variables controlling stream inorganic N concentrations and fluxes, and how they have changed, by synthesizing 20 time series ranging from 5 to 51 years of data collected from forest and grassland dominated watersheds across Europe, North America, and East Asia and across four climate types (tropical, temperate, Mediterranean, and boreal) using the International Long-Term Ecological Research Network. We hypothesized that sites with greater atmospheric N deposition have greater stream N export rates, but that climate has taken a stronger role as atmospheric deposition declines in many regions of the globe. We found declining trends in bulk ammonium and nitrate deposition, especially in the longest time-series, with ammonium contributing relatively more to atmospheric N deposition over time. Among sites, there were statistically significant positive relationships between (1) annual rates of precipitation and stream ammonium and nitrate fluxes and (2) annual rates of atmospheric N inputs and stream nitrate concentrations and fluxes. There were no significant relationships between air temperature and stream N export. Our long-term data shows that although N deposition is declining over time, atmospheric N inputs and precipitation remain important predictors for inorganic N exported from forested and grassland watersheds. Overall, we also demonstrate that long-term monitoring provides understanding of ecosystems and biogeochemical cycling that would not be possible with short-term studies alone.

Our work focuses on the assessment of trends, erosion states and causal risk factors for soil erosion of the Asfalou watershed through the use of the Priority Actions Program/Regional Activity Center (PAP/RAC). This qualitative study model for water erosion makes it possible to assess susceptibility and determine potential fragile areas in order to diagnose the state of soil degradation. We adopted the PAP/RAC crossed matrices, the geographic information system (GIS) and remote sensing (RS) to develop the classical modelling. This method is based on three main approaches: predictive, descriptive and integration. Introducing soil types, slope length (LS) and climatic factors into our model, including rainfall erosivity (R), slope exposure, soil moisture index (SMI) and land surface temperature (LST), improved the reliability of our model. The correlation analysis identified these factors that explain erosion states and the risk of soil erosion. The coefficients of determination (R2) of the various erosive states resulting from the modified PAP/RAC approach explain respectively 98.30%, 77% and 49.3% of the observed variability of the erosive states. These factors provide information on the current state of soil degradation depending on the degree of influence of the different factors that control erosion. The descriptive approach has shown that soil loss manifests itself in different forms, whether for sheet erosion (L) and ravines (C1) successively affecting 79.95% and 17.84% of the land. The integration approach identifies factors and areas requiring intervention to counter the effects of soil erosion in the Asfalou watershed effectively and sustainably.

Hydrologic response in a watershed is driven by precipitation. Multi-site rainfall generators can be used to model watersheds using spatially varied rainfall inputs to better analyze how the rainfall variability affects runoff generation. This study adopted both a single-site rainfall generator (CLIGEN) and a multi-site rainfall generator to generate two rainfall data sequences, which were then used to drive the Soil and Water Assessment Tool (SWAT) for runoff simulation. The 148-km2 Walnut Gulch Experimental Watershed and its two sub-watersheds were selected to evaluate the hydrologic response. Runoff calibration was done against measured runoff in the watershed. Statistics showed that the single-site and multi-site rainfall generators gave similar results regarding annual precipitation. However, the multi-site generator performed much better than the single-site generator in both mean summer flow and for the different return period flows. The runoff derived from the single-site generator was significantly over-estimated in all three watersheds. As for the multi-site generator, the derived runoff was satisfactorily predicted in the smaller watersheds but only overestimated in the largest watershed. This indicated that in small to medium sized watersheds, the spatial variability of rainfall could play an important role for hydrologic response because of the heterogeneity of convective rainfall in this semi-arid region, which makes the application of multi-site rainfall generator a better option than the single-site generator.

This paper presents the results of one of the hydrological models, the InVEST “Annual Water Yield” (InVEST–AWY), applied to the Meta River basin in Colombia, which covers an area of 113,981 km². The study evaluates the performance of the model in different subbasins of the Meta River basin. The model’s accuracy was assessed using different statistical measures, including Nash–Sutcliffe Efficiency (NSE) coefficient, Root Mean Square Error (RMSE), correlation coefficients for the calibration (rcal) and validation (rval) periods. The overall performance of the model in the Meta River basin is relatively poor as indicated by the low NSE value of 0.07 and high RMSE value of 1071.61. In addition, the model explains only a 7% of the variance in the observed data. The sensitivity analysis revealed that a 30% reduction in crop coefficient (Kc) values would result in a 10.7% decrease in water yield. The model estimated, for example, the annual average water yield of the river in 2018 as 1.98 × 1011 m3/year or 6273.4 m3/s, which is 1.3% lower than the reported value. The upper Meta River subbasin shows the highest NSE value (0.49), indicating a good result between observed and simulated water discharge. In contrast, the South Cravo River subbasin shows a negative NSE value of −1.29, indicating poor model performance. The Yucao River subbasin and the upper Casanare River subbasin also show lower NSE values compared to the upper Meta River subbasin, indicating less accurate model performance in these subbasins. The correlation coefficients in calibration (rcal) and validation (rval) for the upper Meta River, Yucao River, South Cravo River, and upper Casanare River subbasins were 0.79 and 0.83, 0.4 and 0.22, 0.5 and −0.25, and 0 and 0.18, respectively. These results provide useful insights into the limitations for the proper use of the InVEST–AWY model in Colombia. This study is the first to use the InVEST–AWY model on a large scale in the territory of Colombia, allowing to evaluate its effectiveness in hydrological modeling for water management.

A compound perspective on hydrological extreme events is of paramount significance as it may lead to damages with larger losses. In this study, an integrated framework, based on downscaled climate variables and hydrological model, i.e. the Soil and Water Assessment Tool, was applied to generate extreme precipitation (Rx1day) and extreme streamflow (Sx1day) series under historical and future climate conditions. Then the potential impacts of climate change for univariate and bivariate joint frequency of extreme precipitation and flood in Xitiaoxi River Basin (XRB), a representative watershed of the Yangtze River Delta, is detected. The compound risk of extreme precipitation and flood under different levels of joint return period for historical and projected periods are estimated by copula‐based two-dimensional approaches. Major findings can be summarized: (1) The Rx1day and Sx1day under future scenarios increased by -0.4 ~ 11.7% and 0.7 ~ 20.4%, respectively, compared to historical period based on univariate frequency analysis, indicating the increasing magnitude of the flood in the future. (2) Climate change with different emission scenarios all have a driving effect on the rising coactivity of extreme precipitation and flood under compound flooding frequency analysis. In addition, the enhancement of climate change to extreme events is more apparent for extremes with higher return period and under the periods of 2080s. (3) Moreover, the flood frequency designs are deduced by bivariate joint distribution are safer than that by univariate distribution. This study may provide actionable insights to formulate the planning scheme of flood control and disaster reduction under the changing environment.

Soil erosion is a serious environmental problem arising from agricultural intensification and landscape changes. Improper land management coupled with intense rainfall has intricated the problem in most parts of the Ethiopian highlands. Soil loss costs a profound amount of the national GDP. Thus, quantifying soil loss and prioritizing areas for conservation is imperative for proper planning and resource conservation. Therefore, this study has modeled the mean soil loss and annual sediment yield of the Gumara watershed. Landsat 5 TM, Landsat 7ETM+, and Landsat 8 OLI were used for land use land cover (LULC) change analysis. Besides these, other datasets related to rainfall, digital soil map, Digital Elevation Model, reference land use, and cover (LULC) ground truth points were used to generate parameters for modeling soil loss. The watershed was classified into five major land-use classes (water body, cultivated land, grazing land, built-up and forest and plantation) using a maximum likelihood algorithm covering a period of the last 30 years (1988–2019). The mean annual soil loss and sediment yield were quantified using RUSLE, Sediment delivery ratio (SDR), and Sediment Yields models (SY). The analysis result unveils that within the past 30 years, the watershed has undergone significant LULC changes from forest & plantation (46.33%) and grazing land to cultivated land (31.59%) with the rate of −1.42km2yr-1 and -2.80km2yr-1 respectively. In the same vein, the built-up area has expanded to cultivated and grazing land. Subsequently, nearly 15% (207 km2) of the watershed suffered from moderate to very severe soil loss. On average, the watershed losses 24.2 t ha−1 yr−1 of soil and yields 2807.02 t ha−1 yr−1 sediment. Annually, the watershed losses 385,157 t ha−1 yr−1 soil from the whole study area. Among the admirative districts, Farta (Askuma, Giribi, Mahidere Mariam and Arigo kebeles), Fogera (Gazen Aridafofota and Gura Amba kebeles), East Este (Witimera kebele), and Dera (Gedame Eyesus and Deriana Wechit kebeles) districts which cover 50% of the watershed were found severely affected by soil erosion. Thus, to curve back this scenario, soil and water conservation practices should prioritize in the aforementioned districts of the watersheds.

Lack of appropriate agronomic practices is one of the major causes for soil erosion and low yields in teff (Eragrostis tef [Zucc.]) production in Ethiopia. A 3-yr study was conducted at the Aba Gerima watershed in northwestern Ethiopia, to investigate the effects of two tillage practices (reduced tillage [RT] and conventional tillage [CT]), two planting methods (row planting [RP] and broadcast planting [BP]), and two compaction options (with [+T] and without [–T] trampling) on soil loss and teff yields in a split-split plot arrangement. Sediment concentration ranged from 0.01 to 5.37 g L⁻¹ (mean, 0.25 g L⁻¹) in our study. Accordingly, the estimated total (August–October) soil loss ranged from 0.2 to 0.5 t ha–¹ (mean, 0.3 t ha–¹). The sediment concentration and total soil loss were significantly influenced (P

More frequent extreme rainfall events associated with global climate change cause greater challenges for soil conservation. Severe erosion occurs on many unpaved roads since these structures create important water flow paths during heavy storms. The present research aimed to investigate the intensity and influencing factors of unpaved road erosion under varied land use and management conditions (sloping cropland, terraced cropland, forest & grass). The erosion occurred in the watersheds contributing runoff water to roads after the greatest rainfall event recorded in the mountain area of northern China caused by Typhon Lekima. The research was conducted in an agricultural-forest-dominated watershed based on field investigation and UAV-based image analysis. A road erosion level classification standard was given according to the occurrence of rills, ephemeral gullies, and gullies. Significant erosion happened on 67% of the unpaved roads; 42% of them suffered moderate to severe erosion in which ephemeral gullies or gullies developed. The average erosion amount from these roads was 2280.75 t ha-1 and was significantly influenced by the watershed land use type and management. The dominant factor governing unpaved road erosion associated with terraced cropland was vegetation coverage on roads. Drainage area was the most important factor for road erosion in sloping cropland and forest & grass land, and road gradient was also a critical factor. Terraces, and forest & grass in drainage areas significantly reduced unpaved road erosion by 85% and, 47%, respectively, compared to sloping cropland. More integrated measures should be used to prevent unpaved road erosion. The results of this research can be applied to road protection against erosion in heavy storms.

As an important soil and water conservation engineering measure, more than 100,000 check dams are constructed across the Loess Plateau; these dams play a vital role in reducing floods and sediment in the region. However, the effects of check dams on hydrologic process are still unclear, particularly when they are deployed as a system for watershed soil and water management. This study examined the watershed hydrologic process modulated by the check dam system in a typical Loess Plateau catchment. By simulating scenarios with various numbers of check dams using a distributed physically-based hydrological model, the effects of the number of check dams on runoff generation and concentration were analyzed for the study catchment. The results showed that the presence of check dams reduced the peak discharge and the flood volume and extended the flood duration; the reduction effect on peak discharge was most significant among the three factors. The system of check dams substantially decreased the runoff coefficient, and the runoff coefficient reduction rate was greater for rainstorms with shorter return periods than for rainstorms with longer return periods. The check dams increased the capacity of the catchment regulating and storing floods and extended the average runoff concentration time in the catchment that flattened the instantaneous unit hydrograph. This study reveals the influencing mechanism of check dam system on the watershed hydrological process under heavy rainstorm conditions and provides a theoretical basis for evaluating the effects of numerous check dams on regional hydrology and water resources on the Loess Plateau.

Modelling the hydrological characteristics of watershed is a method of understanding behavior and simulating the water balance components of watershed for planning and development of integrated water resources management. The soil and water assessment tool (SWAT) physically based hydrological modelling was used for modelling hydrologic characteristics of the Hangar watershed. The data used for this study were digital elevation model (DEM), land use land cover data, soil map, climatological and hydrological data. The model calibrated and validated using measured streamflow data of 13 years (1990-2002) and 9 years (2003-2011) respectively including warm-up period. The SWAT model performs well for both calibration (R2 = 0.87, NSE = 0.82 and PBIAS = +1.4) and validation (R2 = 0.89, NSE = 0.88 and PBIAS = +1.2). The sensitivity analysis, which was carried out using 18 SWAT parameters, identified the 13 most sensitive parameters controlling the output variable and with which goodness-of-fit was reached. The analysis results indicated that the watershed receives around, 9.6%, 59.9%, and 30.5% precipitation during dry, wet and short rainy seasons respectively. The received precipitation was lost by 9.6 %, 40.5%, and 41.3% in the form of evapotranspiration for each seasons correspondingly. The surface runoff contribution to the Watershed were 3.8%, and 79.2% during dry and wet seasons respectively, whereas, it contributes by 17.0% during short rainy seasons.

Advances have been made in water resource investigation due to the implementation of mathematical models, the development of theoretical frameworks, and the evaluation of sustainability indices. Together, they improve and make integrated water resource management more efficient. In this paper, in the study area of the Duero River Basin, located in Michoacan, Mexico, we schematize a series of numerical indices of the Watershed Governance Prism to determine the quantitative status of water governance in a watershed. The results, presented as axes, perspectives, and prisms in the Axis Index, Water Governance Index, and Watershed Governance Prism Index, provide the conclusion that it is possible to establish and evaluate the Watershed Governance Prism Index using our numerical implementation of the Watershed Governance Prism theoretical framework. Thus, it is possible to define a quantitative status and evoke how water governance is being designed and implemented in a watershed.

Most studies of land use effects on solute concentrations in streams have focused on smaller streams with watersheds dominated by a single land-use type. Using land cover as a proxy for land use, the objective of this study was to determine whether the hydrologically-driven response of solutes to land use in small streams could be scaled up to predict concentrations in larger receiving streams and rivers in the rural area of the Little Tennessee River basin. We measured concentrations of typically limiting nutrients (nitrogen, phosphorus), abundant anions (chloride, sulfate), and base cations in 17 small streams and four larger river sites. In the small streams, total solute concentration was strongly related to land cover -- highest in streams with developed watersheds, lowest in streams with forested watersheds, and streams with agricultural watersheds were in between. In general, the best predictor of solute concentrations in the small streams was forest land cover. We then predicted solute concentrations for the river sites based on the solute--land cover relationships of the small streams using multiple linear regressions. Results were mixed -- some of the predicted river concentrations were close to measured values, others were greater or less than measured concentrations. In general, river concentrations did not scale with land cover-solute relationships found in small tributaries. Measured values of nitrogen solutes in the river sites were greater than predicted, perhaps due to the presence of waste water treatment plants. We attributed other differences between measured and predicted river concentrations to the heterogeneous geochemistry of this mountainous region. The combined complexity of hydrology, geochemistry, and human land-use of this mountainous region make it difficult to scale up from small streams to larger river basins. National Science Foundation [DEB0823293, DEB9632854, DEB0218001] Published version National Science Foundation, Grant/Award Numbers: DEB0823293, DEB9632854,DEB0218001 Public domain – authored by a U.S. government employee

International audience; The critical zone (CZ) includes natural and anthropogenic environments, where life, energy and matter cycles combine in complex interactions in time and space. Critical zone observatories (CZOs) have been established around the world, yet their limitations in space and duration of observations, as well as the oft-existing dominant disciplinary research field(s) of each CZO may limit the transferability of the local knowledge to other settings or hinder integrative CZ understanding. In this regard, this review advocates for cross-site cross-network collaborations in CZ sciences. We posit that this type of collaboration is becoming indispensable for understanding past trends and future trajectories of the CZ, in the context of fast-developing and widespread environmental changes. Aided by a series of cyberseminars and a community survey, we highlight some of the existing cross-site initiatives, tools and techniques, and the cross-cutting science questions that could benefit from such cross-network syntheses, in various types of CZ settings (montane, alpine, arctic, managed and agricultural environments, lakes, wetlands, streams, landscapes disturbed by drought and/or wildfire, etc.). This review also identifies and discusses the major and legitimate concerns and obstacles for a collaborative CZ approach, including data harmonization and integration of social sciences, and proposes tentative ways forward. © 2023 The Authors

Soil and water conservation practices have been extensively used in effective watershed management. The impact of each conservation practice is site specific and dependent on the implementation site in the watershed. In order to select cost effective placement of conservation practices with high impact, a large number of spatial combinations is needed to be compared. In this study, an optimization model framework is presented to find cost effective solutions for sediment yield and runoff control in the Fariman dam watershed in the Northeast of Iran. This was accomplished by integrating soil and water assessment tool (SWAT) for simulation of watershed hydrology and multi objective genetic algorithm (NSGA-II) for spatial optimization of soil and water conservation practices. The optimized solutions provided a trade-off between the two objective functions. The final Pareto-optimal shows that the impact of soil and water conservation practices on sediment yield is more than stream flow. The trade-offs between the objective functions show that the implementation of the median cost can lead to a significant decrease of 22.1% in the amount of sediment yield, and 10% in stream flow. Also, percent change achieved through median cost is very close to percent reduction with the highest cost. Results of low cost solution show that the vegetative practices are a suitable economic scenario for soil and water conservation. The introduced framework can be adapted as a suitable tool for selecting cost effective conservation practices in different regions.

China suffers from frequent water crisis events caused by ecological pollution in watersheds. The river chief system policy is an institutional innovation by the government to deal with the ecological environmental crisis in the river basin. This study focuses on China's watershed environmental governance policy and describes the origin, operation mode, and governance effect of its river chief system policy. This study comparatively analyses the advantages of the policy in basin environmental governance, such as clear government responsibility, enhanced coordination among government departments, the accountability mechanism of the one-vote veto system, and the disadvantages of the policy in terms of high costs, information asymmetry, and lack of public participation. Furthermore, this study proposes suggestions on the sustainable development of watershed environmental governance from three aspects: regional characteristics, investment, and institutional innovation of policy implementation. HIGHLIGHTS The innovation system of river management in China is introduced.; The Chinese experience was discussed.; The advantages of the Chinese system are analyzed.; The disadvantages of the Chinese system are analyzed.; The corresponding policy suggestions are put forward.

Morphometric analysis is a pertinent scientific approach in any hydrological analysis, and it is necessary in the progress and management of drainage basin. Identification of areas at risk of erosion, and the prioritization of 48 sub-watersheds of Inaouene basin, was done by using linear, relief and areal aspects of watershed. The research carried out the use of geographic information system spatial data. The linear aspects include stream number, stream sequence, stream length, and bifurcation ratio, mean length of stream order, stream length ratio, mean stream length ratio, and form factor. The areal aspect includes frequency of stream, drainage density, texture ratio, channel length constant, and overland flow maintenance length. Ultimately, the relief dimensions included relief proportion, relief and ruggedness number. The array of compound (Cp) values computed allow us to set the priority ranks and classify the sub-watershed into three priority ranks groups: low, moderate, and high priority. Such morphometric analyses can be used therefore as a watershed erosion status estimator to prioritize land and water conservation initiatives and natural resources management.

Identification of critical source areas (CSAs) is pivotal for the management of nonpoint source (NPS) pollution of watersheds. Most studies focus on source (S) factors and ignore the driving (D) factors of such pollution. The Soil and Water Assessment Tool (SWAT) model and the export coefficient method (ECM) were incorporated to quantify the S factors of ammonia nitrogen (NH4-N) and total phosphorus (TP) as NPS pollution. Specifically, S factors coupled with D factors, including precipitation, slope, soil and land use, were regarded as multi-factors. Moreover, the analytical hierarchy process (AHP) method was adopted to determine the respective weights of multi-factors after overlaying the factor maps to identify the CSAs. These CSAs accounted for 23.86% of the total area, and generated 54.94% of NH4-N and 42.59% of the TP loads. In contrast with single and multi-factors, we found that using multi-factors having differing weights was more accurate for identifying CSAs. Our study results indicate this approach is reasonable for CSAs' identification in watersheds, and it can provide insights into different pollution sources and migration, thus providing a sounder basis for future decision-making. HIGHLIGHTS SWAT-ECM was incorporated to quantify nutrient loads in the watershed.; Both source and driving factors were used to identify CSAs.; AHP method can calculate the weight of different factors.; Considering multi-factors can improve the accuracy of CSAs identification.

Study region This research is carried out in the Kabompo Basin, a headwater catchment of the Zambezi Basin which has an area of 67,261 km2. Kabompo River originates in North-Western Province of Zambia between the Zambezi and Congo River Basins. Study focus This study focuses on error propagation of the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center-MORPHing (CMORPH) rainfall product on simulated streamflow. Assessments are based on automated multi-objective calibration of the Representative Elementary Watershed (REW) model (2006–2012). Parameters of the model were optimized using the ɛ-NSGAII algorithm. Assessments on error propagation targeted streamflow modelling for hydrograph shape and volume, specific hydrograph characteristics, and water balance composition. New hydrological insights for the region By use of multiple objective functions, this study shows that uncorrected CMORPH results in substantial augmentation of rainfall error to streamflow simulation mismatch whereas bias corrected estimates result in attenuation of error. This study shows that analysis for water balance composition has great potential to improve application of satellite precipitation products in water management and decision making in the Zambezi basin. This study advises optimization of model parameters for each respective rainfall input data source so to identify outcomes and effects of respective rainfall data sources on the simulated water balance. Optimization of parameter sets by ɛ -NSGAII results in optimal parameter sets that attributes to findings on the water balance composition and closure.

Recreational water use is an important source of human enteric illness. Enhanced (episodic) surveillance of natural recreational waters as a supplement to beach monitoring can enrich our understanding of human health risks. From 2011 to 2013, water sampling was undertaken at recreational sites on a watershed in eastern Canada. This study compared the prevalence and associations of human enteric pathogens and fecal indicator organisms. Beach water samples had lower pathogen presence than those along the main river, due to different pollution sources and the hydrological disposition. Pathogen profiles identified from the beach sites suggested a more narrow range of sources, including birds, indicating that wild bird management could help reduce public health risks at these sites. The presence and concentration of indicator organisms did not differ significantly between beaches and the river. However, higher concentrations of generic Escherichia coli were observed when Salmonella and Cryptosporidium were present at beach sites, when Salmonella was present at the river recreational site, and when verotoxigenic E. coli were present among all sites sampled. In this watershed, generic E. coli concentrations were good indicators of potential contamination, pathogen load, and elevated human health risk, supporting their use for routine monitoring where enhanced pathogen testing is not possible. HIGHLIGHTS Enhanced surveillance of recreational waters can supplement water quality monitoring and inform our understanding of what contributes to the risk of human illness.; Water collected at reservoir beaches was less contaminated than sites along the main river.; Subtyping of pathogens at the beach sites suggested a narrow range of sources.; The nature of the sampling site influenced the prevalence and types of pathogens.

The present study aims to propose an integrated watershed development plan for the Wainganga basin situated in Maharashtra, India. Also, the study involves evaluating the performance and applicability of SWAT (Soil and Water Assessment Tool) as a runoff model along with the trend analysis of rainfall for the above mentioned study area. The decadal land-use/land-cover (LULC) variation from 1985 to 2005 has been studied using data procured from Goddard Earth Sciences Data and Information Services Center (GES-DISC) and the groundwater table level of the study area was monitored using dug/bore well data collected from the Central Ground Water Board (CGWB). Rainfall trend analysis for a period of 101 years using historic rainfall data procured from the India Meteorological Department (IMD) has been analyzed to foresee the future scenario. It was observed that the rainfall-runoff relationship of the area is getting affected by the LULC variation and is thereby affecting the groundwater regime. There is a significant deterioration in the forest cover and water bodies which is alarming. The study devises the importance of an immediate master plan to be implemented in the basin to avoid any future crisis. Also, the study emphasizes the advancement of remote sensing in the use of hydrologic models like SWAT more realistically.

Multiple rivers flowing into the same bay can be correlated in water quality management and together determine the environmental status of the bay. Nonpoint source pollution management for multi-watershed aiming to alleviate environmental contamination as well as yield considerable economic and environmental benefits can be under additional challenges. In this study, a Bayesian simulation-based multi-watershed effluent trading designing model (BS-METM) is established for multi-watershed nonpoint source pollution management through incorporating techniques of water quality simulation, uncertainty analysis with Bayesian inference, optimal design for effluent trading, as well as mechanism analysis. BS-METM is capable of reflecting parameter uncertainties in nutrient simulation, disclosing the detailed optimal trading schemes under the impact of uncertainties and vital factors, and identifying optimal effluent trading mechanisms through revealing interaction among trading processes of multiple watersheds. BS-METM is applied to a real case of adjacent coastal watersheds (i.e. Daguhe and Moshuihe watersheds), which are identified as major sources of total phosphorus and ammonia nitrogen loadings to Jiaozhou Bay, China. Effluent trading optimization under multiple mechanisms, including intra-watershed trading, cross-watershed trading and non-trading, are conducted. The optimized industry scales and trading processes are obtained. The effects of vital factors on the trading process (i.e. environmental allowance-violation risk level and water availability level) are investigated. The interactions between water availability level and trading mechanism are also analyzed. It is proved that non-trading mechanism would be recommended under low water availability level and cross-watershed trading mechanism would be recommended under medium and high water availability level. The results provide a solid scientific basis for nonpoint source pollution management as well as effective sustainable development for multi-watershed region.

The hydrology of mountainous watersheds in the western United States is significantly influenced by snow year-round. It is widely known that topography affects precipitation; however, the knowledge of how watershed rainfall designation methods affect streamflow is not well understood for high-relief areas. The objectives of this study were to assess the predictive capability of the Agricultural Policy/Environmental eXtender (APEX) model to simulate streamflow in a snowmelt-dominated watershed with high spatial rainfall variability through (a) allocating weather stations to sub-basins based on a conventional Thiessen polygon method (CM) or a rainfall-elevation-based input (RE) and using an areal average Parameter-Elevation Regression on Independent Slopes Model (PRISM) rainfall designation and (b) improving the snowmelt processes in the Price River watershed, Utah. The updated APEX model with snowmelt parameters significantly improved spring flood simulation. The RE was the most robust method in snowmelt and seasonal streamflow simulations compared with the CM and PRISM rainfall designations. Adapting the APEX model to simulate snow-dominant complex terrains will provide crucial water quantity and quality predictions for reliable environmental and watershed management assessment.

The impact of land-use land-cover (LULC) change on soil resources is getting global attention. Soil erosion is one of the critical environmental problems worldwide with high severity in developing countries. This study integrates the Revised Universal Soil Loss Equation model with a geographic information system to estimate the impacts of LULC conversion on the mean annual soil loss in the Temeji watershed. In this study, LULC change of Temeji watershed was assessed from 2000 to 2020 by using 2000 Landsat ETM+ and 2020 Landsat OLI/TIRS images and classified using supervised maximum likelihood classification algorithms. Results indicate that the majority of the LULC in the study area is vulnerable to soil erosion. High soil loss is observed when grassland and forest land were converted into cultivated land with a mean soil loss of 88.8 and 86.9 t/ha/year in 2020. Results revealed that about 6,608.5 ha (42.8%) and 8,391.8 ha (54.4%) were categorized under severe classes in 2000 and 2020, respectively. Accordingly, the soil loss severity class is directly correlated with the over-exploitation of forest resources and grasslands for agricultural purposes. These results can be useful for advocacy to enhance local people and stakeholder's participation toward soil and water conservation practices. HIGHLIGHTS The integration of the Revised Universal Soil Loss Equation model and geographic information system is highly applicable to estimate the impacts of LULC conversion on the mean annual soil loss.; LULC and topography are the main key factors that influence soil erosion in the highland areas.; Agricultural encroachment to forest and grassland is the major factor that aggravates soil erosion.; There is a direct relationship between slope length and erosion rate.

This study assessed the applicability of Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) as rainfall input in watershed modeling using the Soil and Water Assessment Tool (SWAT). The CHIRPS and ground-based rainfall data were used to calibrate and validate the SWAT model in four selected watersheds from each of the four Climate Types in the Philippines. The SWAT performed adequately with CHIRPS across sites during calibration (R2 > 0.74, NSE > 0.71, PBIAS between −6.92 and +12.92, and RSR 0.68, NSE > 0.67, PBIAS between −4.24 to 13.13, and RSR < 0.57). The SWAT models of small watersheds with rainfall inputs from both weather stations and CHIRPS exhibited almost similar results. The ground-based rainfall from one station was not enough to achieve reliable SWAT simulations of streamflow in relatively large watersheds. The CHIRPS proved to be an adequate rainfall source for watershed modeling and can be used as an alternative or supplementary SWAT input in small and large watersheds. This study may serve as a useful reference for water resources managers, policy, and decision-makers in dealing with sparse rainfall monitoring network that is of utmost importance in water resources planning.

The study is carried out to understand the impact of the land-use change in terms of alteration in flow regimes, which are understood to be a leading cause of ecological and environmental deterioration in riverine systems. Meenachil river in the humid tropical region of Kerala, India, is one of a kind river with human settlement along the banks for all its 78 kms of flow through the Kottayam District. The analysis of streamflow from four stream gauge stations was done using Range Variability Approach. The analysis was down as a two-time period analysis with the parametric approach with the period separation taken according to prior studies on land-use change. The analysis shows a high degree of alteration, which can be attributed to the land-use change and can be understood as the root cause for the deterioration of water quality and also the ecological distress, which is well documented in the downstream and watershed regions of the river. HIGHLIGHTS Anthropogenic changes in tropical river basins.; Extreme water conditions.; Modification Indicators Hydrological study.; Environmental flow components.; Flooding and its repercussions.

Understanding the spatiotemporal characteristic of flash floods is significant for the reasonable and accurate identification of high-risk regions of disasters as well as future prediction of hydrological regimes. Therefore, this study collected time-series datasets (1979-2015) of historical flash flood events, rainfall, and land-use in the Hengduan Mountains region, China to characterize the spatiotemporal variation in flash floods affected by the change in rainfall and land-use. Using linear trend, a significant increase with 12 times/10a for flash flood events was found while 82% of events occurred in the flood season (June–August). They were closely related to the increase in frequency (3.5 d/10a) and magnitude (215.55 mm/10a) of heavy rainfall as well as the amplified artificial (999 km2). Affected by heavy rainfall due to climate change and human activity, significant periodic variations on the scales of 3-7a, 8-15a, and 21-31a were derived based on the Morlet wavelet analysis. Meanwhile, utilizing the standard elliptical difference, we identified the moving route of the gravity center of flash floods, with the direction from northwest to southeast. More recorded disasters generally were found in the south of the Hengduan Mountain region, where was mainly controlled by frequent rainstorms and the formation of more cropland and artificial with higher runoff potential. These findings can be an appropriate supplement for lack of understanding of the spatiotemporal dynamics of flash floods in the Hengduan Mountains region and could provide policymakers with evidence to identify high-risk areas which is difficult to cope with in the mountainous watershed.

The lahars generated at the active Tacana Volcanic Complex (Mexico–Guatemala) can be particularly dangerous for three reasons: (1) the high altitudinal gradient between the volcano (4080 m asl) and the surrounding areas (sea level); (2) its location within one of the regions with the highest annual precipitation in Mexico (exceeding 4000 mm) prone to extreme rainfall events; and (3) its capability of ejecting large amounts of pyroclastic material as revealed by its past eruptive activity. In order to estimate the risk, eruptive, climatic, and spatial analyses were carried out at the watershed level associated with the TVC (Coatan, Cahoacan and Suchiate), which constitutes the basis for 89 simulations with nine volumes of lahar (from 3 × 105 m3 to 4.0 × 107 m3) using the numerical model TITAN2D (Two Phase Pitman-Le), considering debris and hyperconcentrated flows. The results show that lahars with volumes greater than 1.0 × 107 m3 and 2.0 × 107 m3 in the Coatan and Cahoacan watersheds, respectively, can reach distances greater than 30 km downstream along the main rivers, affecting Tapachula city and more than 100,000 thousand inhabitants. The threatened areas were spatially correlated with the physical vulnerability associated with the infrastructure (houses, bridges) of the different exposed localities in order to determine the risk level. The risk maps indicate that the localities at the high-risk level represent 25, 6.8 and 5.5% of the communities in the San Rafael Caldera (Guatemala), Cahoacan, and Suchiate (Mexico) watersheds, respectively. The localities at the medium-risk level represent 27.7% in the San Rafael Caldera, and a range of 2.2–2.8% in the rest of the watersheds. Some localities might be affected by lahars originating in different watersheds. This work represents a very valuable instrument for risk management and for preparing mitigation plans for this hazard.

The Soil Conservation Service Curve Number (SCS-CN) model is widely used to estimate the watershed runoff. However, the model may result in inaccurate estimations when assuming a tabulated CN value...

In today's conditions, where the frequency of events related to global climate change is increasing, it is important to employ water science to utilize water with maximum efficiency and to keep water under control in the areas close to its consumption zone. It is also important to determine how much of the flow in the stream during dry periods is the baseflow and how much of it is direct flow. This study designed a model of the baseflow index (BFI) and the baseflow rate (Qb) in one of the watersheds in Turkey. The smoothed minima method designed by the United Kingdom Institute of Hydrology (UKIH) was used to calculate the BFI and Qb at 10 flow observation stations in the Çoruh watershed. The Çoruh Watershed Baseflow Model was designed using BFI and Qb values with watershed characteristics and other variables. The determination coefficient of the BFI model was calculated as R² = 0.842, and the Qb model determination coefficient was calculated as R² = 0.99. The usability of the Çoruh model was proven by using the UKIH's smoothed minima method and comparing its relative errors with the BFI and Qb in the Çoruh model.

Wildfire is a major driver of nitrogen (N) cycling and export from terrestrial to aquatic systems. While fire is a natural process in many watersheds, it can still degrade water quality by rapidly flushing N to streams. This can be particularly problematic in watersheds that experience high levels of N deposition or where climate change is promoting larger and more severe fires. The extent and duration of postfire N export, and the potential consequences for downstream water quality, depend on how N inputs, internal cycling, and outputs vary before, during, and after fire. Here we review the major factors controlling N cycling and retention in forests and adjacent shrublands, and how fire modifies these controls. We connect burned slopes to streams to describe how fire exports N to aquatic environments. We also consider the implications for municipal watersheds and water resources management. We close by identifying critical knowledge gaps in projecting how fire will affect watershed N cycling and retention in the future.

Watershed morphometry refers to the connections between systems of a watershed, such as hydrology, geology, vegetation, and topographic structure. The topographic and hydrological characteristics o...

The conjunction of heavy snowfall during winters and intensive rainfall during monsoons along with the mountainous topography expose the Lidder watershed to serious erosion and flood aggravation issues. Barely any attempts have been made for an in-depth examination of the Lidder watershed for precise estimation of sub-basin level runoff and erosion. In this study, the Soil and Water Assessment Tool (SWAT) was calibrated using the Sequential Uncertainty Fitting algorithm (SUFI-2) for modelling streamflow and sediment yield of the Lidder watershed. Daily runoff and sediment event data from 2003–2013 were used in this study; data from 2003–2008 was used for calibration and 2009–2013 for validation. Model performance was evaluated using various statistical tools, which showed good results revealing excellent potential of the SWAT model to simulate streamflow and sediment yield for both calibration and validation periods. The annual rate of average upland sediment drawn from the watershed was approximately 853.96 Mg/ha for an average surface runoff of 394.15 mm/year. This study identifies the vulnerable areas of the Lidder watershed, which can be thoroughly examined by decision-makers for effective management and planning. Further, the calibrated model can be applied to other watersheds with similar characterization to influence strategies in the management of watershed processes. HIGHLIGHTS Kashmir valley is vulnerable to natural hazards.; Assessment of hydrological processes is a significant test for watershed planning.; SWAT model has proven to be an effective tool for prediction of streamflow and sediment yield of mountainous watersheds with complex topography.; Increased degree of soil erosion in the Lidder watershed may be attributed to steep slopes and atrocious land use of its upland sub-basins.

Evaluating the hazards of debris flows is necessary for risk assessment. The May 12, 2008 earthquake in Wenchuan County, China caused many landslides and loose slopes. Under continuous or heavy rainfall, the landslides and loose slopes are easily destabilized and provide huge amounts of material source for debris flows, significantly increasing the hazard level of associated disasters. Moreover, the hazard of debris flows is not always constant, but variable over time because of the changes in influencing factors (e.g., geomorphology, rainfall conditions, and earthquakes). This study proposes a coupled model based on the TRIGRS (Transient Rainfall Infiltration and Grid based Regional Slope-stability Model) and Flow-R (Flow path assessment of gravitational hazards at a Regional scale) models for a dynamic hazard assessment of debris flows applied in a small watershed, Bayi Gully. This coupled model considers the impact of the actual rainfall process, potential debris sources on slope surfaces, and existing loose sources in the debris flow channel. The results indicate that (1) the hazard assessment by the coupled model is superior to that by the static Flow-R model; (2) the spatial distribution of landslides, debris flow sources, debris flow hazard areas, hazard probability, and debris flow energy vary with rainfall duration; and (3) the debris flow hazard area is strongly affected by topographic and geomorphic factors. Thus, the coupled model provides a powerful and robust tool for the hazard assessment and disaster prevention and mitigation of debris flows.

This paper explores how spatial judgments impacted planning and policy-making by studying how stakeholders on Cape Cod, Massachusetts considered cross-scale relationships between local, regional, a...

One of the most influential environmental variables is rainfall which has significant effect on water resources management, agricultural development, hydrology, and climate change studies. Due to high spatiotemporal variability of rainfall, its monitoring network design can be considered as a useful tool to improve the efficiency of recorded rain gauge stations within the study area. In this study, a new methodology of augmentation of rain gauge network is developed using coupled Block Kriging (BK) and entropy theory methods. In the proposed method, a nested approach of a two-stage positioning of rain gauge stations has been demonstrated. In the first stage, large-scale or fast positioning was done in which the optimal number of candidate blocks was identified. Then, local scale or fine-tuned positioning was done in the second stage. In this stage, to develop the network, accurate locations of rain gauge stations in each block are determined. Besides the main point of this paper, the effect of two kriging estimators, BK and Ordinary Kriging (OK), on the developed network has been investigated and compared. The study area is the Namak Lake watershed with various climates and altitudes. To assess the performance of the optimal rainfall network, three diagnostics were utilized; spatial distribution of annual precipitation, Estimation Error Variance (EEV) maps and histograms. Based on the results, 30 (more than 30% percent of the current stations) rain gauge stations have been proposed scattered over the watershed. Evaluation of the results has shown that the augmented rain gauge network proposed by the BK method outperformed dramatically that of the OK method. EEV maps and also statistical analysis of EEV values confirms the EEV value reduction of almost 25% in augmented network, as well.

Glacier-dependent streams and irrigation systems in the Hood River Watershed (HRW) are particularly vulnerable to climate change, as glaciers retreat and snowpack declines. We developed a system dy...

Protection areas are commonly delineated in water supply watersheds to manage anthropogenic activities that pose pollution risks. These areas are frequently determined based on geographical distanc...

We investigated the potential influence of land-use and climate change on urban hydrology for an urbanized watershed located in Columbia, South Carolina (USA). The Personal Computer Storm Water Man...

Soil erosion is one of the most critical hazards adversely affecting both environment and economy. Assessment of the annual soil erosion rate provides information on soil erosion risk zones indicating the areas with high, severe and low risks. Modelling and prediction of soil erosion has a long history of more than seven decades. It becomes imperative to be familiar with the quantum of studies conducted and methods employed across the world to assess vulnerability of ecosystems to soil erosion to plan strategies for their conservation. There are several methods based on various factors like land use, soil quality, topography etc. available to assess the susceptibility of a region to soil loss. With time the gap in understanding of such models and their use around the world has increased. Numerous models for assessing soil erosion exist but there is a lack of knowledge on spatial distribution of the methods being used. Academic papers related to assessment of soil erosion vulnerability published during the past three decades (1991–2019) were reviewed. Total 160 studies were reviewed to understand advances in the methods used to assess soil erosion vulnerability worldwide, identification of the most popular methods and proportion of studies conducted in the fragile region of Himalayas. The results show that 18 different methods have mainly been used to assess soil erosion risk in different regions. These methods include statistical, physical, process based and empirical models. The use of few physical methods like ANSWERS and SHE has decreased with time while that of physical and process methods like RUSLE, SWAT, WEPP and PESERA has increased with time. The review highlighted that various models being used worldwide are based on their suitability to the region. It also brings to attention that few models like PESERA, EUROSEM and WEPP are mostly being used concentrated in a particular region. Models like PESERA and EPM are mostly used in European region and may be encouraged to estimate soil erosion in Himalayan region. The review also highlights lack of studies with inclusion of water quality as an important parameter while assessing soil erosion vulnerability in the region. The review suggests that in case of lack of data, various statistical methods like PCA, CF, FUZZY etc. can be preferred for qualitative assessment over quantitative assessment. Considering availability of accurate input, researchers need to attempt more methods and perform comparative studies to attain accurate results for assessing soil erosion vulnerability leading to strategizing soil conservation in fragile regions.

Due to the fact that one of the important ways of describing the performance of basins is to use the hydrological signatures, the present study investigates the effects of climate change using the hydrological signatures in Azarshahr Chay basin, Iran. To this end, the Canadian Earth system model (CanESM2) is first used to predict future climate change (2030–2059) under two Representative Concentration Pathways (RCP2.6 and RCP8.5). Six signature indices were extracted from flow duration curve (FDC) as follows: runoff ratio (RR), high-segment volume (FHV), low-segment volume (FLV), mid-segment slope (FMS), mid-range flow (FMM), and maximum peak discharge (DiffMaxPeak). These signature indices act as sorts of fingerprints representing differences in the hydrological behavior of the basin. The results indicate that the most significant changes in the future hydrological response are related to the FHV and FLV and FMS indices. The BiasFHV index indicates an increase in high discharge rates under the RCP8.5 scenario, compared to the baseline period, and also the RCP2.6 scenario. The mean annual discharge rate, however, is lower than the discharge rate under this scenario. Generally, for the RCP8.5 scenario, the changes in the signature indices in both high discharges and low discharges are significant. HIGHLIGHTS Prediction of future runoff under two RCPs using SDSM and SWAT models.; Six signature indices were used to investigate the hydrological behavior of the basin.; Annual precipitation, temperature, streamflow and six signature indices of the RCPs were compared.; The most significant changes in the future of hydrological response are related to high flows.

The Precipitation-Runoff Modeling System (PRMS) was used to develop a simulation of watershed hydrology on the island of Puerto Rico for the period 1981–2017, concentrating on the Río Grande de Arecibo, a river with some of the highest streamflows on the island. This development is part of the U.S. Geological Survey’s (USGS) National Hydrologic Model (NHM) infrastructure which supports coordinated, comprehensive, and consistent hydrologic modeling at the watershed scale for the coterminous United States (CONUS). A goal of the NHM program is to expand the domain outside of CONUS, leading to a PRMS application in Puerto Rico. This model was used to simulate the effects of Hurricane Maria on daily streamflow and provide information at locations where streamgages were damaged by the hurricane. Comparisons with streamflow estimates made by indirect methods in the field, up to ten times higher than simulated values, lends insight into the uncertainties in both the indirect methods and model simulated values and helps to identify potential error in the daily streamflow estimates. The PRMS can be applied to look at the effects of changes in climate and land use, water management, industrial and public water usage, and many other factors that affect hydrology on the island of Puerto Rico. The model is also designed as a support tool for the USGS National Water Census which provides comprehensive reporting of national information on withdrawal, conveyance, consumptive use, and return flow by water-use category.

The present study aimed to analyze the spatial–temporal variation of water streams using Quality Indexes of the Minas Gerais Institute of Water Management (WQI-IGAM), compared with physical–chemical and biological variables established by the CONAMA Resolution 357/2005 employed for water classification. A water stream in the city of Cachoeira-Alta, State of Goiás, Brazil was used as a case study. Four sampling points along the water course were planned; at each point, the variables of dissolved oxygen (DO), temperature (T) and hydrogen potential (pH) were analyzed, using portable equipment, and samples were collected for laboratory analyses of the variables total phosphorus (TP), biochemical oxygen demand (BOD), total nitrogen (TN), turbidity (Turb), total residues (TR) and thermotolerant coliforms (TC). The waters were classified as of poor quality in relation to the variables TP and TC. The water course was classified as class 3 for the results of TP, class 2 for the results of BOD and TC and class 1 for the results of the other variables, according to CONAMA Resolution 357/2005. It is expected that the watershed management bodies will have a greater concern in the supervision of these resources, requiring greater protection of riparian forests and adequate management of watersheds.

In order to identify the seasonal variations and dominant driving factors of NO3-N in rivers, investigations of five consecutive years were conducted in seven rivers of the Miyun Reservoir Watershed. Significant seasonal variation of NO3-N in rivers was separately found in the dormant season (non-growing season) and the growing season. Furtherly, the V-shaped, W-shaped, and indistinct seasonal patterns of NO3-N accounted for 53.0%, 38.7%, and 8.3%, respectively. They were remarkably affected by stream flow, and their significant quadratic function was discovered. The annual maxima and minima of NO3-N corresponded to medium flow in the dormant season and low flow or flood in the growing season, respectively. On one hand, flood mainly played a role in the diluent for the Chao River with high NO3-N, and on the other hand, it acted as a nitrogen source for the Bai River with low NO3-N. The NO3-N was closely correlated with human activities, and this correlation had obvious seasonal change trend. In the dormant season, significant and mostly extremely significant high correlation coefficient (R) values were determined, while partly non-significant with low R values were found in July, August, September, and October. Increasing seasonal variation index of NO3-N from upstream to downstream was found that was gentle for large rivers and sharp for small tributaries. The seasonality of NO3-N was more affected by natural factors, especially flood, than human factors.