ABSTRACT This study delves into morphometric and morphotectonic analyses to unveil the evolutionary trajectory of Kerala's Korapuzha river basin. Employing advanced GIS and remote-sensing techniques, we explore the basin's geomorphological evolution and landform development. Our approach integrates data from a 1:50,000 scale toposheet and a 30 m resolution Digital Elevation Model (DEM), facilitating a detailed evaluation of basin characteristics. Through subdivision into KB-1 and KB-2 sub-basins, distinct morphometric patterns and morphotectonic features are discerned. The elongated basin configuration suggests ongoing tectonic activity, profoundly shaping its unique geomorphic evolution. To unravel tectonic influences, we employ morphometric indices, including the Relative Active Tectonic Index (IRAT), revealing neo-tectonic activity and dynamic landscape changes. Our study enriches our understanding of the Korapuzha river basin's evolution, illuminating the interplay between tectonic forces and geomorphic processes. Offering insights into tropical river systems, it contributes to broader landscape dynamic comprehension and informs sustainable land management practices. The IRAT calculation for the Korapuzha basin is based on the average of five geomorphic index classes, with resulting classifications indicating varying levels of tectonic activity. KB-1 and KB-2 sub-basins’ IRAT values enumerated as 2.2 and 2, respectively hence fall into classes 4 and 3, indicating low and moderate tectonic activity, respectively. The presence of tectonism in the study area revealed from geomorphic indices and IRAT, was acknowledged and evinced precisely by following the analysis of the SL index and GLA index method.

ABSTRACT Groundwater is one of the most important sources of freshwater, contributing significantly for drinking and other domestic activities around the world. However, its quality is deteriorating over time due to overexploitation and anthropogenic activities. Rib watershed is located in the Tana basin (Ethiopia), is intensively cultivated and urbanizing area. Therefore, this study attempted to assess groundwater vulnerability to pollution using the GIS-based Modified DRASTIC Model. The modified DRASTIC model was selected due to it incorporates both hydrogeological parameters and anthropogenic factors for assessment. The necessary data were collected from the field, and downloaded from websites and laboratory experiments (No3 -). The results showed that more than 73.24% of the watershed is under medium to high vulnerability. Highly vulnerable areas of the watershed (22.48%) was confined to the Southern parts of the watershed (under built-up and cultivated areas). Based on single parameter sensitivity analysis, its vulnerability was highly influenced by aquifer media (24.1%), net recharge (21.75%), land use/land cover (15.1%), and depth of groundwater table (13.6%). The Modified drastic model was validated based on the observed data of nitrate concentration in groundwater. Based on the observed data of nitrate concentration, high-vulnerable areas were more contaminated than medium and low-vulnerable areas. The modified drastic index has a strong correlation with nitrate concentration with (r = 0.76) and (P < 0.043). Therefore, the result indicated that the area is vulnerable to contamination calling for appropriate groundwater management. Hence, this finding helps to plan and minimize future contamination of groundwater by considering its vulnerability before high-risk activities are allowed.

ABSTRACT The Nile River is one of the longest rivers in the world, serving as the lifeline of many countries. The river is subjected to significant anthropogenic pressures, and thus, understanding the magnitude of contamination and its possible consequences is needed. This research aimed to evaluate the presence of heavy metals in the surface water of an understudied region within the Nile River. The distribution and level of 18 elements along the Damietta branch were assessed, and their potential sources were estimated. Additionally, pollution indices and health risks were calculated. The results showed that most metals were within the acceptable levels of USEPA and WHO. However, Na, Mg, and Ca were higher than the permissible level of WHO, and K was higher than the permissible levels for irrigation. Furthermore, heavy metal pollution indicators, degree of contamination indices, heavy metal evaluation indices, Nemerow pollution indices, and water quality indices all pointed to very high standards for water quality. Also, the noncarcinogenic health risk index indicated a safe limit for dermal and oral exposure for adults and children. Overall, this study recommends management focus on anthropogenic activities in the Damietta branch of the Nile River.

ABSTRACT Accurate prediction of stream flow is essential for effective water resource management, particularly in regions with complex hydrological dynamics. The Mille River, which flows through this basin and has a watershed area of 4,862.3 km², plays a crucial role in the region's water resources. However, selecting the most suitable hydrological model for this task remains a challenge due to varying model performances. This study addresses the problem of identifying the most effective hydrological model for predicting stream flow in the Mille River by evaluating three models: Soil and Water Assessment Tool (SWAT), Hydrologiska Byråns Vattenbalansavdelning (HBV-IHMS), and Artificial Neural Network (ANN). The objectives are to compare these models’ abilities to simulate daily stream flow and to determine their accuracy. The significance of this evaluation lies to guide water management decisions by identifying which model provides the most reliable predictions. The methodology involves using performance metrics, Nash-Sutcliffe Efficiency (NSE) values, to assess the accuracy of each model. The results show that SWAT achieved the highest NSE values of 0.81 and 0.82, indicating the best performance in simulating stream flow. ANN followed with NSE values of 0.79 and 0.81, while HBV-IHMS had lower NSE values of 0.73 and 0.74. Although all models demonstrated potential, SWAT and ANN outperformed HBV-IHMS in capturing the complex hydrological processes of the Mille River. The findings from this study indicate that the choice of model significantly impacts the accuracy and reliability of streamflow predictions. The SWAT and ANN models show strong potential for use in operational streamflow forecasting in the Mille River and similar basins. In conclusion, further research is recommended to refine model calibration and validation processes. Incorporating additional data sources, such as remote sensing and climate projections, could further enhance model accuracy and provide a more comprehensive understanding of the region's hydrological dynamics.

ABSTRACT Land degradation is a significant global environmental issue, and its prevention has become a serious concern of the twenty-first century, particularly in the context of anthropogenic impact and climate change. It is crucial to map and assess the grade of land degradation to determine vulnerable areas. The Indian Himalayan region faces heightened risks with its steep terrain, active tectonics, heavy precipitation, and human interventions. This study focuses on the Nandakini Watershed. Employing AHP technique, the study calculates the Land Degradation Vulnerability Index (LDVI) using slope, terrain ruggedness, rainfall, temperature, LULC, soil depth, and organic carbon content. The results indicate that the upper region is highly vulnerable, and a higher slope influences the runoff in the area, followed by factors like NDVI and rainfall, collectively contributing to 62% of the overall index. In this context, the upstream regions of the watershed display a high LDVI, while most of the area falls within the low LDVI category. This indicates that approximately 2.10% of the study area is highly susceptible to soil erosion. RUSLE-based estimates have been used to further validate the LDVI result. The integrated LDVI offers a valuable tool for prioritising soil conservation and disaster mitigation.

ABSTRACT Building flood reduction dams for territory protection is very often necessary as it allows the reduction of peak flows during flood events by creating a storage in upstream areas. An online structure with such characteristics is outlined, presenting one or more openings in order to allow normal and moderate flows to pass downstream. A stilling basin is provided downstream of the openings and, on one side of the flooded area, a spillway weir is set. For low river flows, the openings will act as free-surface weirs. The openings are equipped with a sill in such a way to let the discharge independent of the downstream flow conditions. For moderate flood flows, the water level upstream of the dam will rise, and the openings will become submerged, effectively behaving as an orifice arrangement. For large flood flows, the crest of the flood spillway weir is reached and they will be discharged via both the orifice structure and the flood spillway structure. The silled openings and the stilling basin are one only hydraulic complex. Since no examples exist of their behavior as a whole, the aim of this paper is to give the designers the opportunity to size them given the basic requirement of the flood reduction dam, i.e. the max discharge allowed downstream. For this reason, the paper will focus on the opening discharge coefficients, the stilling basin energy dissipation and water level. Both the orifices and the stilling basins were studied starting from the hydraulic models of three dams that were built in Calabria (Italy). The structures of the stilling basins are original. The results appear in dimensionless form and offer useful guidance for similar hydraulic cases, with the exception of specific terrain related issues. Finally, an example of a preliminary design of orifices and stilling basin is presented.

ABSTRACT The watersheds are fundamental in the management of social policies, allowing for the measurement of physical and socioeconomic characteristics through indicators such as the HDI and SII. This study aims to develop the Socioeconomic Analysis Indicator (SAI) for the sub-basins of the Sorocabuçu River (SRB), using a fuzzy system and geoprocessing tools for zoning information by sub-basins. The HDI of the SRB resulted in high values, with income showing the lowest indices, followed by education and longevity. The SII showed low values, with income and literacy significantly contributing to socioeconomic vulnerability. The SAI results indicated reasonable socioeconomic conditions, with lower values in the sub-basins farther from urban and urbanized areas. This study provides data for the establishment of public policies aimed at reducing social and economic inequalities, prioritizing the most vulnerable sub-basins. The data obtained serve as an effective tool to support public management, promoting decisions that improve the quality of life of the local population through the integration of socioeconomic variables for a more holistic and sustainable approach to watershed management.

ABSTRACT Sustainability requires understanding and respecting the ecosystem functioning to plan the use of its resources. Improvised planning plus economic benefits can stimulate unsustainable decisions that lead to complications and obscures the application of appropriate adaptations when a change is required. This paper is a historical review of a reservoir when the dam changes its use from hydroelectric to water supply and then tourism is superimposed on the ecosystem. Data collected from the literature are systematically analyzed to see the effects on basin-reservoir dynamics. The main effect was the increase in the hydraulic retention time of the reservoir that facilitates the accumulation of nutrients and eutrophication, aggravated by the increase in the fixed and floating population stimulated by tourism. The consequent cyanobacteria blooms deteriorate the landscape, become a health risk and cancels the use of the reservoir to tourism. The increase in emerging compounds detected in the treatment plant effluent discharged into the reservoir poses a risk to aquatic species and the water supply. These results are analyzed in light of the objectives and dimensions of Sustainability. Recommendations include modifying Goal 1 of SDO 8, because it is shown that an annual growth of 7% of GDP in developing countries threatens their natural resources.

ABSTRACT Reliable estimates of sediment fluxes into rivers provide valuable information for current and future water resource development and management. In this study, empirical equations relating discharge to suspended sediment loads were developed for the three major tributaries (Black Volta, White Volta, and Oti) of the Volta Lake. The empirical equations were fed with projected future river discharges for the three tributaries, to estimate the suspended sediment fluxes into the Volta Lake for the future (2051–2080) relative to a baseline period (2014–2016). The Soil and Water Assessment Tool (SWAT) was used to model the projected discharges. The SWAT model was driven by downscaled climate projections from two regional climate models (RCA4 and RACMO22 T) forced by two emission scenarios (RCP 4.5 and RCP 8.5) from the IPCC Fifth Assessment. Compared to the baseline, the estimated future sediment fluxes show average increments of about 19% and 28%, respectively under RCP 4.5 and RCP 8.5. This has negative consequences as less water is stored for hydropower generation and the lake water becomes more turbid, which inhibits zooplankton and fishery production. The result underscores the need to improve the management of the Lake's watershed by ensuring proper landcover/use planning, afforestation and enforcing regulations on land degradation and general environmental conservation.

ABSTRACT Strategic flood risk management of river catchments involves significant increases in the complexity both of the contents (e.g. the aims and measures) of a given strategy and also its social, spatial, and temporal scales. Conceptually, flood risk management research to date has underestimated the importance of time and temporality. This paper, which is based on ‘historical Institutionalism,’ introduces a temporal lens to focus on strategic flood risk management; it highlights issues of duration and timing as well as tempo and change in tempo with respect to the implementation of measures to reduce flood risk at catchment level. The application of a temporal lens is illustrated through empirical research into strategic flood risk management for the medium-sized Aist river catchment in Austria. The paper uses a longitudinal qualitative research design to analyze the changes in strategic flood risk management in the catchment. The analysis shows that strategy efforts in reaction to an extreme flood event in the catchment in August 2002 can be differentiated into three phases. Phase 1 is characterized by the design of ambitious catchment-wide management; Phase 2 by struggles to implement the strategy due to institutional conditions and protests by citizens; and Phase 3 by redesign of the initial strategic plan to make it less ambitious and by changes to the actor constellation supporting the plan. The present paper offers a process-oriented institutional explanation for this pattern of phases, and it highlights issues of timing and tempo. It concludes with general suggestions for enhancing the temporal dimension in flood risk management.