Watershed Assessment Research Articles

Soil erosion risk assessment of the Lakhmess watershed (northwestern Tunisia) via the SEAGIS model: Inferred prioritization of risky sub-watersheds

Water erosion in Tunisian semi-arid regions causes harmful effects by silting reservoirs and reducing agricultural lands and soil fertility. Several factors are involved in the erosion process: rain erosivity, soil fragility, and degraded land cover on steep slopes associated with the intensification of inappropriate human practices. Thus, identifying erosion vulnerable sub-watersheds based on the assessed soil loss rate is very important to apply suitable conservation measures. The current research aimed to prioritize risky areas in the Lakhmess watershed, north-west Tunisia via the Soil Erosion Assessment using Geographical Information System (SEAGIS) model. To prioritize sub-watersheds vulnerable to soil erosion and sediment yield, the Lakhmess watershed, covering an area of 162 km2, was divided into 16 sub-watersheds (L1–L16), according to the hydrographic network. Then, the mean annual soil erosion rate and the mean annual sediment yield in the watershed were estimated by integrating the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) in the SEAGIS model and their spatial distribution was determined. The obtained results indicate that the estimated average annual soil erosion rate is 4.2 t/ha/y and the annual sediment yield is 2.6 t/ha/y. Maner's SDR model was selected as the best model for estimating SY, with standard error, standard deviation, and coefficient of variation values of 0.75%, 0.01, and 0.45%, respectively. The prioritization of the Lakhmess sub-watersheds based on the estimated soil loss rate reveals that among the 16 sub-watersheds, three sub-watersheds (L10, L12, and L15) were identified as being in a very high priority soil erosion class. The high soil erosion rate and sediment yield in these sub-watersheds is explained by the steep slope and a high rainfall erosivity factor. Six sub-watersheds (L2, L4, L5, L6, L7, and L16) were found to belong to a very low priority soil erosion class, as they are characterized by a very gentle slope, which appears to be an extremely determining factor. These findings constitute a basis for decision makers to plan effective conservation measures to conserve agricultural lands, soil, and water resources in northwestern Tunisia.

Integration of Watershed eco-physical health through Algorithmic game theory and supervised machine learning

The eco-physical health assessment of watersheds is crucial for sustainable water resource management and ecosystem services. This study quantifies the eco-physical health of the Talar watershed in Iran using the geometric mean method (GMM), game-theoretic algorithm (GTA), and machine learning algorithms including Random Forest (RF), Support Vector Machine (SVM), Simple Linear Regression (SLR), and K-Nearest Neighbor (KNN) for distributed and semi-distributed monitoring. The results show that the RF algorithm performed better than other models, as indicated by MAE, MSE, RMSE, and AUC statistics with values of 0.032, 0.003, 0.058, and 0.940, respectively. The watershed health index prioritization with different approaches showed that the pattern of watershed health changes positively from upstream to downstream. Based on the watershed health prioritization using GMM, it can be said that sub-watersheds Int6 and Int5 are the healthiest sub-watersheds in the studied watershed, with values of 0.93 and 0.90, respectively. Based on the watershed prioritization using the GTA approach, it can also be said that sub-watersheds Int6, Int5, and Int01 are the healthiest ones. In the case of the RF algorithm, the average values of the pixels in each sub-watershed showed that sub-watersheds Int6 and Int01 were recognized as the healthiest sub-watersheds with values of 0.91 and 0.88, respectively. Int6 consistently emerged as the healthiest sub-watershed across all methods, attributed to high TWI and NDVI values and low slope, DEM, erosion, and CN values. In general, it can be said that the watershed health index in the studied catchment fully followed the factors affecting the catchment's health and that the spatial patterns of change of this index were consistent with the physiographic and hydroclimatic conditions in all three semi-distributed and distributed approaches. The study's implications underline the importance of multi-criteria and multi-algorithm approaches in accurately assessing and managing watershed health for sustainable development.

Advancing freshwater science with sensor data collected by community scientists

Autonomous sensor networks providing real‐time data are growing in popularity with community scientists due to instant availability of high‐frequency data. What role does this monitoring play in watershed assessment alongside agency‐run monitoring programs? How accessible, interoperable, and reusable are the data for other researchers? We compared a community science‐led stream monitoring network—EnviroDIY—in the Delaware River Basin, in which more than 50 watershed organizations have deployed more than 100 stations monitoring temperature, electric conductivity, depth, and sometimes turbidity, with the Basin's US Geological Survey (USGS) stream gauge network. The EnviroDIY network (n = 124) complemented the USGS network (n = 102) by monitoring sites with different watershed sizes and land‐use distributions. Although data were accessible and interoperable using a web data portal, community scientists had difficulty sharing metadata that would enable data reuse outside this project and they required support analyzing these large datasets to understand threats to watershed conditions. We address those needs here with a conceptual framework for interpreting data and communicating results.

AquaNutriOpt: Optimizing nutrients for controlling harmful algal blooms in Python—A case study of Lake Okeechobee

We present AquaNutriOpt, a user-friendly Python package designed to tackle a complex combinatorial optimization problem aimed at optimizing nutrient management for the control of harmful algal blooms. This optimization process involves the identification of optimal Best Management Practices (BMPs) and Treatment Technologies (TTs). AquaNutriOpt is constructed based on a novel integer programming model, which we present in this paper. The package can accommodate various user inputs, automatically transforming them into an optimization model, and then solving it using a free solver. To demonstrate AquaNutriOpt’s efficacy, we conduct a series of experiments on two watersheds around Lake Okeechobee in Florida, USA. These experiments illustrate that the optimal BMPs/TTs obtained by AquaNutriOpt can significantly reduce Phosphorus loads into the lake across various budget scenarios. We validate the results by running simulations with the process-based Watershed Assessment Model (WAM), confirming that the estimated percentage reductions closely align with the reports from WAM.

Spatial-temporal Evolution and Driving Factors Analysis of Ecological Environment Quality in Daihai Basin based on AWRSEI

Watersheds are an important ecological security barrier and social and economic development area. In order to evaluate the ecological environment quality of arid and semi-arid watersheds more objectively and accurately, based on the remote sensing ecological index (RSEI), the salinity index was introduced to construct a remote sensing ecological index (AWRSEI) suitable for arid and semi-arid watersheds, and the Daihai watershed was taken as an example to analyze its applicability. Based on the AWRSEI model, four phases of Landsat TM/OLI composite images were used to quantitatively evaluate the ecological and environmental quality of the Daihai Basin from 2001 to 2020. The spatio-temporal evolution of the ecological and environmental quality of the Daihai Basin was analyzed using the coefficient of variation and spatial autocorrelation, and the cause analysis and driving factor explanation power analysis were carried out using geographic detectors. The results showed that:① the average correlation coefficient between AWRSEI and various ecological factors was 0.860, which was more representative than that of a single index component. The load positive and negative values and ranking of the first principal component were consistent with those of RSEI, the contribution rate of eigenvalues was 3.69% higher than those of RSEI, and the evaluation results were closer to the real surface conditions, which is suitable for the ecological environment quality assessment of arid watersheds. ② The annual average of the AWRSEI index in the Daihai Basin from 2001 to 2020 was 0.427, which indicated a poor ecological environment quality basis. During the study period, the average of AWRSEI showed a fluctuating trend and reached the highest value of 0.502 in 2020. The overall ecological environment quality improved significantly, the deterioration area decreased by 20.51%, and the improvement area increased by 12.71%. In terms of spatial distribution, the ecological environment quality of forest land in the southern and northwestern high-altitude areas of the Daihai Basin was good, whereas that in the northern and southern mid-altitude areas was poor, and that in the northern area was better than that in the southern area. ③ The average variation coefficient of AWRSEI in the Daihai Basin was 0.280, the ecological environment quality was stable, and the overall change fluctuation was small; the high fluctuation was mainly concentrated in the southern part of the lake and the residential area. There was a significant spatial autocorrelation in the ecological environment quality of the Daihai Basin, and the high-high agglomeration area was mainly distributed in the forest area at high altitude and the cultivated land area at low altitude. Low-low concentration areas were scattered in the middle altitude area. ④ The improvement of the ecological environment in Daihai Basin from 2001 to 2020 was mainly due to the increase in NDVI and the decrease in NDBSI and NDSI. NDVI and NDBSI were the combination with the strongest interaction and the strongest interpretation of the ecological environment. Land use was the dominant factor of AWRSEI and had the strongest explanatory power. The combination of land use and meteorological factors was the strongest interaction, and the relationship between each driving factor was enhanced.

Landslide susceptibility assessment of the Asi watershed, southern Türkiye

Landslide susceptibility assessment of the Asi watershed, southern Türkiye

Enhanced watershed status evaluation: Towards an integrated framework to assess fish habitat in forested watersheds using airborne laser scanning data

Sustainable forest management is a key component of modern forestry practices; however, an often-overlooked component is watershed health. To support forest management objectives, practitioners need information on the long-term health of riparian and stream ecosystems. Herein we present a framework to assess the condition of, and risks to, riparian and stream ecosystems within two forested fish-bearing watersheds, the Nahmint river and Artlish river, in British Columbia, Canada using airborne laser scanning (ALS) data. To do so, we first, compare the current British Columbia Tier 1 geographic information system (GIS)-based watershed condition evaluation protocol supplemented with a number of stream and watershed attributes derived from ALS data. Second, we use these ALS derived attributes to develop an enhanced Tier 2 watershed status evaluation framework that can be applied to stream reaches, which is a much finer spatial scale than is considered in current assessment approaches. We found that supplementing the existing watershed condition evaluation protocol with ALS-derived stream location, elevation, and canopy height information consistently increased the risk of a reduction in functioning condition being determined by the Tier 1 watershed assessment protocol. Further, we found that the Nahmint watershed had 28%, 65% and 7% of stream reaches with good, fair, and poor overall rankings of habitat condition, respectively. We conclude that ALS derived steam reach attributes can integrate into existing watershed evaluation protocols and provide detail that is critical to making informed management decisions and mitigating the cumulative effects on for example salmon bearing streams. As ALS data become increasingly available, value-added applications of these data, such as the integrated watershed assessment protocol demonstrated herein, can provide useful information to support forest management.

Assessing Hydropower Potential in Nepal's Sunkoshi River Basin: An Integrated GIS and SWAT Hydrological Modeling Approach.

This study assessed the hydropower potential of a mountain watershed within the Sunkoshi River basin in Sindhupalchok, Nepal, utilizing geographic information systems (GIS) and the soil and water assessment tool (SWAT) hydrological model. Topographical, soil, land use, meteorological, and discharge data were employed to assess the study area for the appropriateness of hydropower generation. SWAT was utilized to delineate the Sunkoshi basin into 23 distinct subbasins and involved the creation of a detailed river network, incorporating various hydrological attributes including stream links, stream order, stream length, and slope gradient. After that, it was employed to simulate river discharges within these subbasins. The Sequential Uncertainty Fitting Version 2 (SUFI-2) algorithm, integrated within the SWAT Calibration and Uncertainty Program (SWAT-CUP), was employed to calibrate and validate the model. This step involved the adjustment of 25 selected parameters to enhance the model's accuracy and reliability in representing the hydrological processes of the Sunkoshi basin. Model performance was assessed utilizing three well-established efficiency criteria: coefficient of determination (R2 = 0.79), Nash-Sutcliffe efficiency (NSE = 0.73), and percent bias (PBIAS = 17.59). The study identified 36 sites across streams of order 3, 4, and 5 as having potential for hydropower generation. The hydropower potential at each identified site was evaluated using estimated stream flow and topographical head at various probability of exceedance (PoE) levels (40%, 45%, 50%, and 60%). The aggregate hydropower potential of the basin was quantified, yielding a potential of 371.30 MW at a 40% PoE. The findings suggest that an integrated approach combining SWAT-based hydrological modeling within a GIS can accurately assess a river basin's hydropower potential and provide insights into further evaluation of the comprehensive environmental assessment of the fragile Himalayan watersheds.

Evaluating water quality change with hydrologic restoration in the Western Everglades (Florida, USA), an application of WAM

Hydrologic restoration at the watershed scale is a complex process that can influence other processes and conditions within the watershed and downstream systems. Given these interrelated watershed scale processes, tools like models are essential to assess the potential effectiveness of sub-watershed to regional remediation strategies for ecological restoration. The goal of Everglades restoration is to restore the quality, quantity, and timing of water to one of the most ecologically unique and complex systems. This study aimed to evaluate changes to water quality associated with hydrologic restoration efforts within the Feeder Canal Basin as identified by the Western Everglades Restoration Project (WERP) by demonstrating, through simulations the potential effectiveness of implementing water quality remediation measures such as Best Management Practices (BMPs) and Stormwater Treatment Areas (STAs) within the WERP area. Additionally, to understand potential phosphorus sources and pre-develpoement conditions within the basin, a pre-development baseline was developed. Using the Watershed Assessment Model (WAM) various model alternatives including the WERP tentatively selected plan (TSP) were developed for a 22 year period of simulation. The implementation of both moderate and aggressive BMPs significantly reduced total phosphorus concentrations within the canal system at various levels indicating an improvement to near-field conditions. Meanwhile, not until the moderated BMPs and operation of an STA do water quality improvement become realized further downstream. The combined strategy of BMPs and STA demonstrates the integrated nature of nutrient remediation with both near and far-field benefits to the system with hydrologic restoration. This integrated strategy of water quality and hydrologic restoration can lead to a more sustainable and resilient restored ecosystem.

A Comprehensive Assessment of the Hydrological Evolution and Habitat Quality of the Xiangjiang River Basin

Human disturbance and climatic factors alter the hydrological state of rivers in many ways and have a degree of negative impact on the quality of watershed habitats; quantifying the impact of both human disturbance and climatic factors on hydrological change can help improve the quality of watershed habitats. Therefore, in this research, an integrated watershed assessment framework is proposed to analyse the watershed from four perspectives: hydrological situation, environmental flows, drivers, and habitat quality. A meteorological streamflow model based on the Long Short-Term Memory (LSTM) model was employed to analyse the hydrological evolution and quantify the influence of the drivers from the perspective of hydrological and environmental flows. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model was then used to evaluate the spatial and temporal evolution of habitat quality in the basin. And, finally, the grey correlation theory was used to reveal the response of habitat quality to hydrological changes. Studies have shown that annual flow and precipitation are increasing in the Xiangjiang River (XJR) basin, while its annual potential evapotranspiration is decreasing significantly. After 1991, the hydrological conditions of the XJR were highly variable, with the combined rate of change of the most Ecologically Relevant Hydrological Indicators, ERHIs-IHA and ERHIs-EFCs, reaching 26.21% and 121.23%, respectively. Climate change and human disturbance are the main drivers of change for both (with contributions of 60% and 71%, respectively). Between 1990 and 2020, the habitat quality in the basin declined over time (from 0.770 to 0.757), with areas of high habitat value located mainly in mountainous areas and habitat degradation being concentrated in urban areas in the middle and lower reaches, gradually evolving towards areas of high habitat value in the periphery. There is a strong correlation between watershed habitat quality and the ERHIs. The results of the study can provide a scientific basis for maintaining regional ecological security and rational allocation of water resources.

Hydrological Modelling to Inform Forest Management: Moving Beyond Equivalent Clearcut Area

Forest disturbance can alter the hydrologic conditions of a watershed, including the frequency, magnitude, and timing of peak and low flows. Equivalent Clearcut Area (ECA) has been routinely used in watershed assessments to estimate hydrologic alteration due to forest disturbance. ECA analyses typically rely on broad regional assumptions, qualitative observations, and/or expert judgement, making it difficult to provide accurate quantitative estimates of hydrologic change. Process-based hydrological models offer an improved approach since they replicate watershed processes, can simulate land cover and climate change scenarios, and provide quantitative estimates of hydrologic change, including at ungauged points of interest. A workflow using a regionally calibrated hydrological model to investigate forest disturbance and future climate change scenarios is demonstrated. Results are contrasted with ECA-based outputs and emphasize that in addition to the amount of forest disturbance, watershed physical characteristics and the location of disturbance within a watershed influence the hydrologic response. This approach provides forest managers with quantitative outputs that support risk-based forest management decisions and presents a substantial improvement over ECA-based methods. Keywords: hydrological modelling, ECA-based analysis, watershed assessment, forest disturbance, cumulative effects, risk-based forest management

Erosion and Sediment Transport Modeling: A Systematic Review

Soil erosion and sediment transport have significant consequences, including decreased agricultural production, water quality degradation, and modification to stream channels. Understanding these processes and their interactions with contributing factors is crucial for assessing the environmental impacts of erosion. The primary objective of this review is to identify a suitable soil erosion and sediment transport model for catchment-scale application. The study considers various model selection processes, including model capability and the spatial and temporal domains for assessing spatiotemporal distributions. The review acknowledges the limitations, uncertainties, and unrealistic assumptions associated with soil erosion and sediment transport models. Models are usually developed with a particular objective, which demands an assessment of capabilities, spatial, and temporal applicability, and catchment-scale applicability. Distributed models are often preferred for catchment-scale applications, as they can adequately account for spatial variations in erosion potential and sediment yield, aiding in the evaluation of erosion-contributing elements and planning erosion control measures. Based on the findings of this study, the authors encourage utilizing models (such as Soil and Water Assessment Tool (SWAT) or Automated Geospatial Watershed Assessment Tool (AGWA)) that can forecast net erosion as a function of sediment output for catchment erosion and sediment yield modeling. This review helps researchers and practitioners involved in erosion and sediment modeling by guiding the selection of an appropriate model type based on specific modeling purposes and basin scale. By choosing appropriate models, the accuracy and effectiveness of sediment yield estimation and erosion control measures can be improved.

Evaluation of impacts of climate change on natural and managed wetland basins

AbstractLow floodplain wetlands such as the Western Everglades in South Florida are vulnerable to extreme weather events, and their water quality and ecosystem functions vary greatly depending on changes in water levels and discharges. The future (i.e., the mid and late 21st century) climate is projected to result in increased frequency and magnitude of extreme events, which could negatively affect the hydroecological function of the wetlands. Wetland management practices have commonly been implemented to protect wetlands and their functions, but it is not clear whether the current management practices can still be effective in projected climate change scenarios. The main goal of this study was to evaluate the impacts of climate change on the runoff and total phosphorus (TP) of natural (L28 Gap) and managed (L28) wetland watersheds in the Western Everglades. For the assessment, we employed future climate projections made using 29 general circulation models (GCMs) and the Watershed Assessment Model (WAM), a watershed loading model. The WAM was calibrated and validated for the baseline period (2000–2014), and the bias‐corrected climate projections were incorporated into the model to project the runoff discharge and TP loads for the near‐future (2030–2044) and far‐future (2070–2084) periods in two carbon emission scenarios. The modeling results show that the natural wetland watershed would be more vulnerable to projected climate change than the managed wetland watershed. The impact of projected climate change scenarios on daily runoff and TP loads was modulated by water control facilities and practices in the managed watershed, highlighting the significance of watershed management practices for improved water quality under projected climate change. This study demonstrates how the local natural and managed wetland watersheds distinctly respond to the global‐scale changes and emphasizes the role of water management practices in wetland basins, which are expected to help develop effective climate change adaptation plans for improved sustainability of wetland systems.

Drought Assessment of a Data-scarced Watershed – Quetta Valley, Pakistan

Pakistan continuously remains under the threat of drought, as approximately 88% of its area falls under arid and semi-arid regions. The most affected province due to drought is Balochistan, facing migration, scarcity, famine and economic strain. The insufficiency of meteorolgical and hydrological data in the area intensifies the problem because of the late or non-diagnosis of drought. Therefore, this study proposes a methodology to quantify the drought in a watershed with inadequate meteorological and hydrological data. This study aims to design a method to find the extent and duration of drought conditions for watersheds where only basic meteorological data is available. For this purpose, Quetta Valley, Balochistan, Pakistan, is chosen as the study area. First, the hydrological components of water balance for the watershed are calibrated for 10 years using a distributed hydrological model (MIKE-SHE). The modeling results and other observed meteorological data are then used to evaluate eight drought indices to assess the existence and extent of drought, including those which use the hydrological parameters as input from MIKE-SHE. Reconnaissance drought and Palmer drought severity indices, which use detailed hydrological parameters, are found to provide more accurate results coupled with early drought detection of historical events. The results showed that the proposed method could be effectively used to determine the secondary parameters from the hydrological model, which in turn gives more realistic drought conditions for such regions. KEYWORDS: Meteorological drought indices, Hydrological modeling, MIKE SHE, Drought, Palmer drought severity index.

No-tillage and agroforestry decrease sediment loss from a hilly landscape in northern Morocco

No-tillage agriculture and agroforestry have many environmental benefits, such as maintaining soil productivity, storing water and reducing labor and energy. These practices may also reduce soil erosion in hilly landscapes with a Mediterranean climate by leaving more crop residues on the surface that allow rain and irrigation water to infiltrate the soil profile rather than run off the soil surface. Based on this concept, the objective was to determine how no-tillage and agroforestry techniques affect hydrology and sediment loss from the 180 km2 Tleta watershed in northern Morocco. Land cover and precipitation impact on hydrological processes were quantified with the calibrated Kinematic Runoff and Erosion (KINERO2) model. The KINEROS2 model was validated with data from 7 rainstorms from 2014 to 2018, then soil erosion rates were simulated under extreme rainfall events, considering storm recurrence intervals of 5, 10, 15, 30, 50 and 100 years. The model performed well in the calibration (R2 = 0.8 and Nash–Sutcliffe model efficiency coefficient, NSE = 0.6) and validation (R2 = 0.9 and NSE = 0.7) steps. Then, land use scenarios were tested with the Automated Geospatial Watershed Assessment (AGWA) tool for conventional agriculture (baseline scenario), no-tillage agriculture, agroforestry and combined no-tillage and agroforestry (alternative scenarios). Annual sediment loss of 5.7 t. ha−1 with conventional farming declined by 63 %, to 2.1 t. ha−1 for the combined no-tillage and agroforestry practices. We conclude that adopting no-tillage plus agroforestry on vulnerable farmland has the potential to significantly reduce soil erosion and diminish the sediment yield at the Tleta watershed outlet.

Three Decades of Road and Trail Runoff and Erosion Work in the Northeastern Caribbean – a Research Program Perspective

HighlightsThe infiltration capacities of unsurfaced roadways are frequently exceeded by rain intensity, promoting overland flow.Erosion rates from unsurfaced roadways and cut slopes are 101 to 104 times greater than on undisturbed hillslopes.Roads in steep, subtropical wet terranes may increase landslide erosion by a factor of 5 relative to areas without roads.The hydro-geomorphic impact of roads is so prominent that they must be explicitly considered in watershed assessments. ABSTRACT. Erosion is a key environmental concern in the northeastern Caribbean because it can diminish soil productivity, damage infrastructure, and threaten human life. Additionally, sediment released by erosion can be delivered to streams where it can degrade water quality and aquatic habitat, reduce reservoir storage capacity, and threaten critical marine resources such as sea grass beds and coral reefs. Road erosion has been a concern in the region since the 1990s, and a considerable body of research has been conducted over the last ~30 years. This article reviews the key findings and identifies additional research needs. In some tropical dry coastal watersheds of the US Virgin Islands and Puerto Rico, unpaved roads and foot or off-road vehicle trails are the primary sediment sources. Watershed scale sediment production rates in these tropical dry settings are 0.3 to 3.7 Mg ha-1 yr-1, depending on unpaved road density, and these are 3 to 40 times greater than under undisturbed conditions. In wetter settings, like the forested and actively cultivated landscapes of highland Puerto Rico, sediment contributions include those from unpaved farm roads but also those from croplands, streambanks, and landslides. Watershed scale sediment production rates in actively cultivated tropical wet settings are 15 to 60 Mg ha-1 yr-1, with road-induced surface erosion and landslides accounting for 50% to 95% of total sediment production. Designing management alternatives will require additional research to improve our understanding of road-to-stream and road-to-coast connectivity, develop effectiveness metrics of applied management practices, and establish the specific causes of road-induced landslides. Keywords: Connectivity, Coral reefs, Landslides, Puerto Rico, Sedimentation, Surface erosion, Virgin Islands.

Health assessment of The Upper Citarum Watershed, West Java, Indonesia

Citarum watershed is one of the national priority watersheds. Watershed health assessment activities are used as a reference in efforts to restore watershed conditions and improve watershed management planning. The watershed health was assessed for the Upper Citarum watershed in West Java, Indonesia. Three indicators, including hydrology and land cover were used to assess the watershed health. Hydrology indicators include the Annual Flow Coefficient (KAT) and River Regime Coefficient (KRA). Watershed health level assessment was conducted using Analytical Hierarchy Process (AHP) scoring method. Watershed health levels such as very unhealthy, unhealthy, moderately unhealthy, healthy, and very healthy were obtained by calculating each indicator total number of scores. From the health assessment result of The Upper Citarum watershed, the Annual Flow Coefficient indicator shows an unhealthy level, and River Regime Coefficient indicator shows very unhealthy level. In addition, the land cover indicator shows unhealthy level. Thus, because of a decreased vegetation cover over ten years. Based on the AHP weighting, it was found that The Upper Citarum watershed is at a very unhealthy level. Therefore, according to government regulations about proper watershed management, land cover vegetation must be managed to increase conservation and water quantity to maintain the Citarum watershed’s sustainability.

MORPHOMETRIC CHARACTERISTICS OF A TROPICAL RIVER BASIN, CENTRAL KERALA, INDIA USING GEOSPATIAL TECHNIQUES

The Thutapuzha watershed (TW) is one among the major tributaries of Bharathapuzha – the largest west flowing river in Kerala, India. Morphometric analysis was carried out to determine the spatial variations in the drainage characteristics and to understand the prevailing geologic variation, topographic information and structural setup of TW using Survey of India topographic maps and ASTER-DEM. Geoprocessing techniques has been used for the delineation and calculation of the morphometric parameters of the watershed. The TW sprawled over 1107 Km2 and the study revealed that the watershed includes a sixth order stream and lower order streams mostly dominate the basin with a drianage density of 1.36 m/Km2exhibiting highly resistant subsoil, dense vegetation, and low relief of surface nature. The study indicate that rainfall has a significant role in the drainage development whereas the drainage pattern is controlled by structure and relief. The watershed of TW is moderate to well-drained and exhibited a geomorphic maturity in its physiographic development. The shape parameters revealed the elongated nature of TW having less prone to flood, lower erosion and sediment transport capacities and drainage network development in the watershed. This study strongly brings to light that the drainage morphometric parameters have the enormous potentiality to unveil the hydro-morphologicalcharacteristics of the river basins. Integrating hydro-morphological characteristics with conventional watershed assessment methods would have a beneficial effect on judicious watershed management, which helped to formulate a comprehensive watershed management plan.

Watershed Health Assessment Using GIS and AHP Methods: Application in Stung Sen River Basin, Cambodia

The watershed assessment provides information about the condition of water quality and biological integrity to identify the source of stressors and their impacts. In the present decades, different watershed assessment method has been established to evaluate the cumulative impacts of human activities on watershed health and aquatic systems. This study proposes a new approach for assessing watershed vulnerability to contamination based on spatial analysis using the Geographic Information System (GIS). and Analytic Hierarchy Process (AHP) methods. This new procedure designed to identify vulnerable zones depends on seven basic factors representing watershed characteristics: land use/land cover, sediment load, nitrate load, phosphorus load, soil type, average annual precipitation, and slope. The new watershed vulnerability assessment technique was used to create a map showing the relative vulnerabilities of specific sub-watersheds in the Sen River Basin, the largest sub-basin of the Tonle Sap Lake. The results showed a remarkable difference in watershed susceptibility between the sub-watersheds in their vulnerability to pollution. The approximate area of 10,846 km2 (76%) in the Northwest part and the long distance from the river of the study area were categorized in a range from moderate, low, and very low watershed vulnerability. However, consisting 3,341 km2 (24%) located downstream and near distance from the river were displayed as a very high and high vulnerability to pollution in the watershed. Furthermore, the results of the evaluation of the predictive reliability of the watershed vulnerability assessment method revealed that the proposed approach is suitable as a decision-making tool to predict watershed health. The process of this study indeed provides an application performance for the Sen River Basin and calls for action to sustain the water ecosystem and use.

Ecological Sustainability Assessment of Water Distribution for the Maintenance of Ecosystems, their Services and Biodiversity

Water provision and distribution are subject to conflicts between users worldwide, with agriculture as a major driver of discords. Water sensitive ecosystems and their services are often impaired by man-made water shortage. Nevertheless, they are not sufficiently included in sustainability or risk assessments and neglected when it comes to distribution of available water resources. The herein presented contribution to the Sustainable Development Goals Clean Water and Sanitation (SDG 6) and Life on Land (SDG 15) is the Ecological Sustainability Assessment of Water distribution (ESAW-tool). The ESAW-tool introduces a watershed sustainability assessment that evaluates the sustainability of the water supply-demand ratio on basin level, where domestic water use and the water requirements of ecosystems are considered as most important water users. An ecological risk assessment estimates potential impacts of agricultural depletion of renewable water resources on (ground)water-dependent ecosystems. The ESAW-tool works in standard GIS applications and is applicable in basins worldwide with a set of broadly available input data. The ESAW-tool is tested in the Danube river basin through combination of high-resolution hydro-agroecological model data (hydrological land surface process model PROMET and groundwater model OpenGeoSys) and further freely available data (water use, biodiversity and wetlands maps). Based on the results, measures for more sustainable water management can be deduced, such as increase of rainfed agriculture near vulnerable ecosystems or change of certain crops. The tool can support decision making of authorities from local to national level as well as private enterprises who want to improve the sustainability of their supply chains.