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The identification of areas prone to soil erosion in ungauged river basins is crucial for timely preventive measures, as erosion causes significant damage by lowering soil productivity and filling reservoirs with sedimentation. This study proposes a novel approach to prioritize sub-watersheds (SWs) in Ponnaniyar river basin. It utilizes different combinations of five objective-based weighting methods and seven Multi-criteria Decision Making (MCDM) techniques under outranking and synthesis methods with soil loss, morphometry, land use/land cover (LULC), and topography parameters. The results obtained from different hybrid models are validated using metrics like percentage and intensity of change. The findings reveal that MW-PROMETHEE (53.85%) and CRITIC-WASPAS (8.31) perform best in prioritizing areas based on morphometry, while CRITIC-TOPSIS (48.35% and 7.58) is more effective in prioritizing areas based on land use/land cover (LULC) and topography. The grade average method is used to integrate the rankings from 71 models: 35 based on morphometry, 35 based on LULC, and 1 based on the RUSLE model. The analysis identifies SW2 with a grade value of 4.34 as severely affected by soil erosion, followed by SW11 (5.45), SW5 (5.56), and SW9 (5.68), all falling within the very high priority level. This study recommends implementing appropriate water harvesting structures, which might be helpful in mitigating soil degradation, promoting soil conservation, and ensuring sustainable agricultural productivity. [ABSTRACT FROM AUTHOR]

Reservoir sedimentation management has become an important topic for large dams in the United States due to their historical design, current age, and increased environmental regulation. Less attention has been paid to small dams (hydraulic size < 0.01) in remote mountains with urgent sedimentation problems. In drier climates, such reservoirs may be frequently drained and trans-catchment flows routed over their sediment deposits heading from one mountain tunnel to another. This study asked an unexplored scientific question focusing on this special setting: how do different amounts of water transfers interact with different reservoir stages to affect sediment erosion and its redistribution in the backwater zone? Mindful timing and magnitude adjustment of water transfer, involving water diverted across watersheds by tunnels, through a reservoir were hypothesized to strategically redistribute sediment erosion for sites with water transfer/diversion facilities in the main channel. For a study site in the north-central Sierra Mountains of California, 2D hydrodynamic modeling revealed that sediment erosion within the backwater zone increased by > 100% when water transfer was maximized, involving a flow 12 times higher than mean annual discharge. With reservoir stage drawdown, the increment of sediment erosion was further increased by > 50% compared with water-transfer-only scenarios. The natural upstream inflow with daily flow occurrence of 5–25% was the optimal water transfer to avoid disturbing sediment. These results indicated that water transfer and stage drawdown optimization is a promising strategy to promote or abate redistribution of deposited sediment through a smaller reservoir.

With increasing emphasis on ecological environment conservation, the conservation of fish habitat and the regional carbon balance need to be incorporated into the operation process of reservoirs. In this research, formulas for calculating ecological and environmental objectives in reservoir operation were obtained by fitting the curve of discharge and fish habitat area and comprehensively analysing the factors affecting reservoir carbon emissions. Additionally, we used the multi-objective optimization algorithm NSGA-II-DE to study the competitive relationship between the economic, ecological, and environmental benefits of the Longtoushi Reservoir and proposed a relatively optimized operation scheme using the multi-objective decision-making method VIKOR. The results of this scheme showed that the power generation, weighted usable area (WUA) and carbon emissions of Longtoushi Reservoir during the study period were 5.74 × 108 kW h, 9.61 × 104 m2 and 51.32 t, respectively. Compared with the relative optimal operation scheme, the power generated by the maximum power generation scheme increased by 2.66%, the WUA decreased by 1.68%, and carbon emissions increased by 9.86%; the power generation of the maximum WUA scheme increased by 0.16%, the WUA decreased by 0.08%, and carbon emissions increased by 0.72%; and the power generation of the minimum carbon emission scheme increased by 3.14%, the WUA decreased by 1.62%, and the carbon emissions increased by 9.14%. In general, competition between power generation, WUA and carbon emissions is inevitable, and reducing the water level in reservoirs can effectively increase ecological and environmental benefits. [ABSTRACT FROM AUTHOR]

Dams accumulate sediment by interrupting the continuity of rivers, resulting in a loss of reservoir water storage capacity and decreased productive life. These issues raise a growing concern about the decreasing benefits of projects. This paper contributes to the implementation of sediment transit strategies and operating rules of reservoirs to reduce overflows and recover the technical–economic viability of sedimented reservoirs by maintaining ecological flow. The main difficulty lies in the fact that sedimentation of the reservoir limits the mobility of dredging equipment and blocks the intake. To regain the viability of the reservoir, the commonly used strategies to manage water resources and reservoir sedimentation were analyzed. To control reservoir sedimentation and restore the generation capacity, different sediment management strategies were implemented and evaluated at the entrance, body of the reservoir and intake; these strategies included reduction of the entry of sediments, restoration of the storage capacity, clearing of the water intake for the turbines to restore power generation, trash rack cleaning during the power generation process and modification of the hydroelectric power plant operating rules to optimize the economic income. The implemented strategies successfully reduced overflows from 88 to 40% in 3 years and stabilized the reservoir storage capacity by balancing the inflow and removal of sediments. Although the water intake for the turbines was cleaned, accumulation increased in other areas of the reservoir. Finally, root cause analysis (RCA) was employed, and solutions were proposed to increase the capacity of the reservoir and reduce overflows to 15%. [ABSTRACT FROM AUTHOR]

Inevitable evaporation and sedimentation will influence reservoir operational performance if the two fluxes have been ignored when sizing reservoir systems. While this is to be expected, very few studies have quantified this influence. This study has analysed the effects of evaporation and sedimentation on reservoirs operational performance. It used seven reservoirs in Yesilirmak Basin, Turkey as case studies. The Dams serve a variety of purposes including irrigation, domestic and industrial, hydropower generation and flood control. Performance with regard to meeting these needs was characterized using reliability (time-based and volume-based), resilience, vulnerability and sustainability. The results showed that while ignoring both the evaporation and sedimentation during planning does affect subsequent operational performance, the influence of evaporation was more significant. Possible reasons are provided for the outcome and ways by which both can be accommodated during planning analyses thus mitigating the operational effects are suggested. [ABSTRACT FROM AUTHOR]

The purpose of the paper is to examine and compare the visions of social and economic development in the area around the newly constructed Mucharz dam reservoir on the Skawa River in southern Poland as represented by both the local community and local authorities. A text mining approach was used to analyse both the information collected through interviews with local residents and documents detailing the development plans for the land surrounding the dam drafted by the local authorities. The results of the study indicate strong mismatches between the ideas for the development of the area surrounding the dam as envisioned by the local authorities and those of the local community. The mismatches refer both to the contents of the plans and to their degree of generality. The authorities focus on general conceptual visions of the area, but the residents expect specific actions and measures to be undertaken. Major discrepancies between the perspectives of both groups of stakeholders can result in residents becoming unsatisfied with the actions taken by the local authorities, poor collaboration between them and even conflicts between the community and the authorities. The text mining methodology applied in the study has been rarely used so far in research on people's perception of dam projects and has proven useful in examining social impact assessment. [ABSTRACT FROM AUTHOR]

Public policies affecting land use/land cover also have an impact on water resource availability, and hilltop protected areas are a relevant factor in ensuring continued availability of water resources. The legislation ruling the delimitation of protected areas on hilltops has changed at the Brazilian national level in 2012 and in Rio de Janeiro state in 2014. However, these environmental legislation changes did not take into account the feedback effects of restricting protected areas to hilltops on the regularity of hydrological responses in watersheds. As such, this manuscript sought to analyze the contribution of hilltop-only protected areas to continued water availability. We analyzed hydrological responses in the São João river watershed, which provides water for domestic, industrial, and agricultural uses in the Região dos Lagos municipalities of Rio de Janeiro state. Our results show that designating only hilltops as protected areas, as prescribed under the new pieces of legislation, does not prevent abrupt changes in hydrological responses that can lead to changes in streamflow volume and regularity as well as increases in sediment flows, which may compromise drainage systems and continued water supply due to reservoir silting. Therefore, we conclude that protecting hilltops only, as established under current Brazilian legislation, is not sufficient to safeguard the environmental function of maintaining water resource availability. [ABSTRACT FROM AUTHOR]

Sedimentation in large reservoirs is a major concern in semi-arid regions characterized by severe seasonal water scarcity. As a contribution to improved sediment management, this study analyses the real case of the reservoir of Sidi Yacoub in the north of Algeria. First, a dynamic model of the reservoir was set up and used to estimate past water and sediment inflows (period 1990-2010) based on data recorded by the dam operator and measurements at a gauging station located downstream of the reservoir. Second, in a stochastic framework using the statistical characteristics of inflow and outflow discharges, a projection of future sedimentation was performed until 2030, assuming stationarity of the statistical distributions. Third, the model was used to investigate the influence of possible climate change and to quantify the positive effects of soil conservation measures upstream. [ABSTRACT FROM AUTHOR]

Reservoir sedimentation is a severe problem because it leads to the loss of reservoir storage capacity. Therefore, the sustainable management of water and sediment constitutes a critical measure in reservoir operation. In this research, a model of similarity-based operation method of water and sediment which can improve the efficiency of reservoir operation strategies is presented. Two parts comprise this method: a similarity-based forecasting model for the sediment process at the dam, and a new operation mode of water and sediment based on the sediment process at the dam. The similarity-based forecasting model is built on the total flow model of water and sediment, which requires less data. Using the similarity among flood cases, the parameters of the model are calibrated by group, and are dynamically selected, an approach which enforces the suitability of parameters and improves the forecasting accuracy. In terms of the sediment process at the dam, the proposed optimal operation model of water and sediment improves the sediment-venting efficiency and saves the water resource. [ABSTRACT FROM AUTHOR]

Importance of existing reservoirs for supplying fresh water has increased significantly due to population increase and enhanced living standards, while the reduced development of new reservoirs in recent decades has made it even more pertinent that the current battery of reservoirs be operated in a sustainable and efficient manner. In order to move a step towards the goal of sustainability, sediment evacuation must be considered when optimizing a reservoir's operations. The Reservoir Optimization-Simulation with Sediment Evacuation (ROSSE) model is a recently developed tool which internalizes sediment evacuation routines and the simulation module in a newly developed GA-based optimization module. This article applies the ROSSE model with the aim of minimizing irrigation shortages in the Tarbela Reservoir, Pakistan. The article also calculates the suitable values of various GA parameters required to run the model through a sensitivity analysis. Simulation results of three sets of rule curves-one existing and two optimized sets-are compared with each other for parameters like irrigation shortage, power generation, sediment evacuation and flood dis-benefits (damages). It is found that the optimized rule curves of scenario 1 reduce the irrigation shortages by 39 % while the optimized rule curves of scenario 2 can reduce the irrigation shortages by 24 % of that of the shortages by existing rule curves. The optimized rule curves of scenario 2 also ensure the current level of hydropower generation and sediment evacuation for the Tarbela reservoir. The study recommends a change in the reservoir's existing rule curves in order to reduce irrigation shortages. The incorporation of the sediment evacuation routine and availability of economic and hydro based objective functions in the optimization model will help achieving the goal of sustainability. [ABSTRACT FROM AUTHOR]

Studies the sedimentation history of the Abbeystead reservoir in England, using a two-dimensional reservoir routing model. Solution to the Navier-Stokes equation coupled to a general sediment transport equation; Determination of water flow and sediment motion.

A limnological survey of a man-made reservoir in the central part of Albania was conducted from May 2006 to May 2008. This water body is being constructed 15 years ago for water supply of the Tirana, capital city of Albania. The physical and chemical quality of water in this reservoir was determined and compared against universally accepted water quality standards. Water quality parameters relevant to the study area are discussed considering the ecosystem function and interrelationship among physical and chemical parameters with the biological ones. The water quality of traditional and modern reservoir was not significantly different except for a bed odour that occurs throughout of the summer. Due to the reservoirs life the eutrophication in the nowadays is not a major problem in the reservoir, but due to an intensive sedimentation rate it is predicted that will seriously affect the water body in the near future. Management strategies to improve the water use efficiency with particular reference to eutrophication are proposed. On the other hand it is recommended that an integrated approach following the IRBM criteria will be the best way of management and administration. [ABSTRACT FROM AUTHOR]

This paper describes a melding of an established set of hydrological component processes to obtain a full-scale model for reservoir sedimentation. The goal is to achieve a probabilistic system relating reservoir sedimentation to standard injection, river flow, particle transport, and dam storage subsystems. In the conclucing section, it is found that for a certain assembly of process components, the sedimentation process is Poisson, with parameters interpretable in terms of physical variables. Moreover, for the resulting parameters, a Gaussian approximation can confidently be adopted. [ABSTRACT FROM AUTHOR]

The cold river water inflow often plunges below the ambient dam reservoir water and becomes density underflow through the reservoir. The hydrodynamics of density currents and plunging are difficult to study in the natural environment and laboratory condition due to small-scale, entrainment and turbulent flows. Numerical modeling of plunging flow and defining of the plunging depth can provide valuable insights for the dam reservoir sedimentation and water quality problem. In this study, an adaptive neuro-fuzzy (NF) approach is proposed to estimate plunging flow depth in dam reservoir. The results of the NF model are compared with two-dimensional hydrodynamic model, artificial neural network (ANN), and multi linear regression (MLR) model results. The two-dimensional model is adapted to simulate density plunging flow simulation through a reservoir with sloping bottom. The model is developed using nonlinear and unsteady continuity, momentum, energy and k-ε turbulence model equations in the Cartesian coordinates. Density flow parameters such as velocity, plunging points, and plunging depths are determined from the simulation and model results. Mean square errors (MSE), mean absolute errors (MAE) and determination coefficient (R) statistics are used as comparing criteria for the evaluation of the models' performances. The NF model approach for the data yields the small MSE (1.18 cm), MAE (0.86 cm), and high determination coefficient (0.95-0.98). Based on the comparisons, it was found that the NF computing technique performs better than the other models in plunging flow depth estimation for the particular data sets used in this study. [ABSTRACT FROM AUTHOR]

Accelerated soil erosion is a threat for the societies due to the loss of ecosystems services. Soil erosion and sediment delivery have been assessed in a small catchment of Central Spain with a new water body, the Pareja Limno-reservoir, located in its outlet. This limno-reservoir was created in 2006 with environmental and recreational purposes in the riverine zone of a large reservoir. Sedimentation risk is an issue of concern regarding limno-reservoirs environmental feasibility. Thus, the study of the soil erosion in the Pareja Limno-reservoir catchment and its sediment delivery seemed of the utmost importance. In this paper we establish an affordable and simple methodology to address it. A soil erosion and deposition monitoring network was installed in the Ompólveda River basin (≈88 km), which flows into the Pareja Limno-reservoir. Results obtained were related with those from a sedimentation study previously carried out in the limno-reservoir. Gross hillslope erosion in the catchment was 6.0 Mg ha year, which is in agreement with values reported for Mediterranean areas. After subtraction of the deposition measured, a soil loss of 1.2 Mg ha year was found in the catchment. Sediment delivery ratio (SDR) was estimated to be 3.8 %. SDR is low as a result of the low connectivity between the stream network and the limno-reservoir. Some local characteristics may also have a secondary influence in the low SDR value. Results obtained support the environmental feasibility of the Pareja Limno-reservoir from the sedimentation risk perspective. They also demonstrate that the methodology followed allows the assessment of soil loss and sediment delivery at a catchment scale, and the identification of areas where the erosion problems are most severe. [ABSTRACT FROM AUTHOR]

The periodic assessment of the revised capacity is essential and conventional techniques through bathymetric surveys and inflow-outflow techniques are time and resource intensive. The application of optical remote sensing data is practiced for a long time to compute the revised capacity of the reservoir but has the limitation of selecting threshold values and inefficacy of the method during the cloudy season. This research proposed the application of the Otsu segmentation technique in Google Earth Engine (GEE) to determine revised water spread using microwave remote sensing data. The Otsu technique is efficient in classifying the image into two distinct classes using within and between-class variances. An application has been developed using Sentinel data in GEE, which has the capacity of cloud-based computing and applied to the four reservoirs of Mahanadi Reservoir Project (MRP) namely Ravishankar Sagar, Murumsilli, Dudhawa, and Sondur reservoir in the Chhattisgarh state of India. The original capacities of these reservoirs vary from 910.51 MCM of Ravishankar (RS) Sagar to 165.89 MCM of Murumsilli reservoir. The revised water spreads computed in the GEE were further used to compute revised volume and in turn the revised cumulative capacities at different levels. The analysis suggested that 17.65% of dead storage (118.26 MCM from 143.00 MCM) and 9.25% of gross storage (85.26 MCM from 910.52 MCM) of RS Sagar has been lost in 42 years (1978 to 2020). Similarly, 10.33% gross capacity of Murumsilli, 13.12% of Sondur, and 12.37% of Dudhawa reservoirs have been lost due to the deposit of sediments from the catchments, and results were found comparable with bathymetric survey results of three reservoirs. The proposed application has been developed in GEE so it can be used in any part of the world in cloudy weather with no human interference. [ABSTRACT FROM AUTHOR]

In this study, we present a long-term water management model which can be an important tool for the ordinary management of a reservoir. The model can be made simple and applicable in a graphic form. The key point of the model is that the sedimentation rate of solids can be modeled according to a power law. The basic equation of the model is tested using bathymetric surveys of different dams located in different parts of the world. Robustness and predictive power are evaluated both numerically and by comparison with satellite results. Then the model is transformed into the form of a management plot and applied to the real case of the Camastra dam. [ABSTRACT FROM AUTHOR]

The aim of this study was to show the importance of exploiting the appropriate sites for construction of dams on the borders of riparian countries. To achieve this aim, a multi-reservoir system was designed across the border of two riparian countries. In addition, simulation models that express the possible operating mechanisms for this system were created. This storage system comprises two reservoirs along the border of Iraq and Turkey. One simulation model of a real reservoir was formulated to prove the model's validity by comparing its output with the observed output of the real counterpart. Three simulation models for the proposed reservoirs were developed by adopting the standard operating policy. The first and second of these three models were built to mimic the operation of the two proposed reservoirs separately, while the third simulation model was formulated to operate these two proposed reservoirs simultaneously as united multi-reservoir system. The results indicated the efficiency of the simulation model for an existing reservoir. In addition, the results of the three simulation models of the proposed multi-reservoir system demonstrated the flexibility of these simulation models in imitating the operation of a storage system, whether it was a single or a multi-reservoir system. According to the results of these three simulation models, the two proposed reservoirs could be significantly beneficial to Iraq and Turkey. [ABSTRACT FROM AUTHOR]

Arid region water reservoirs have different characteristics and solutions from humid regions with the most water shortage in the world socio-economically. This paper outlines possible implementation methodologies, procedures and guidance for water storage in natural and artificial reservoirs for better operation and management rules taking into account the impacts of climate change. The literature is full of methodological applications regarding the impact of climate change on the hydro-meteorological records, but the same is not available in reservoirs (surface and underground), which is the scope of this paper. In addition, reservoir structures offer the necessary mitigation and adaptation activities against the effects of climate change to design, construct, maintain, operate or increase their existing capacity. To increase groundwater reservoir capacity in local aquifers, precipitation, associated flooding and flash flooding should be diverted to artificial groundwater recharges through precipitation and surface runoff harvesting activities. Definitions of fully or partially penetrating underground dams are also explained. The real groundwater feeding application is offered from the Kingdom of Saudi Arabia as arid region representative. Finally, a series of recommendations are presented for the future design and management of reservoirs. [ABSTRACT FROM AUTHOR]

In the last decades, climatic changes in Mediterranean regions and frequent events of water resource scarcity in supply systems have required addressing the problem of increasing the inflows in storage reservoirs by connecting them to diversion dams. Usually, diversion dams do not have a large storage volume; consequently, these works are not able to regulate monthly flow, and they can divert to reservoirs only a part of river flow. In this field of research, this study aims to provide a procedure to evaluate water volumes withdrawn from diversion dams considering river flows and transfer flows. The procedure is founded by analysing 36 gauging stations in Sardinia (Italy), where a unique regional flow duration curve (FDC) can be defined. The effectiveness of regional evaluation of volume withdrawn, based on a monthly time scale analysis, has been investigated. The methodology allows finding optimal values of regional FDC parameters in order to better evaluate water resources withdrawn from diversion dams with respect to the current estimation used in the Sardinia Region Water Plan (SRWP). The current SRWP (RAS 2006) uses a fixed and extremely precautionary value of the FDC that underestimates withdrawal volumes. Moreover, a correlation analysis has been carried out in order to extend the evaluation of optimal FDC parameters for ungauged basins that allows to improve application of this procedure. Obtained results could allow to update the SRWP as highlighted in the final application to a real water system. [ABSTRACT FROM AUTHOR]

An estimation of daily suspended sediment concentration (SSC) is required for water resource and environmental management. The traditional methods for simulating daily SSC focus on modeling the SSCs themselves, whereas the cross-correlation structure between SSC and streamflow has received only minor attention. To address this issue, we propose a stochastic method to generate long-term daily SSC using multivariate copula functions that account for temporal and cross dependences in daily SSCs. We use the conditional copula method to construct daily multivariate distributions to alleviate the complications and workload of parameter estimations using high-dimensional copulas. The observed daily streamflow and SSC data are normalized using the normal quantile transform method to relax the computationally intensive model of building daily marginal distributions. Daily SSCs can thus be simulated through the multivariate conditional distribution using previous daily SSC and concurrent daily streamflow values. The proposed method is rigorously examined by application to a case study at the Pingshan station in the Jinsha River Basin, China, and compared with the bivariate copula method. The results show that the proposed method has a high degree of accuracy, in preserving the statistics and temporal correlation of daily SSC observations, and better preserves the lag-0 cross correlation compared with the bivariate copula method. The multivariate copula framework proposed here can accurately and efficiently generate long-term daily SSC data for water resource and environmental management, which play a critical role in accurately estimating the frequency and magnitude of extreme SSC events. [ABSTRACT FROM AUTHOR]

Although sediment is one of the most common causes of stream impairment in the United States, soil erosion is not integrated into many surface water management models. In this work, a module is developed to estimate fluvial erosion within an existing surface water optimization model. This model is applied to the Lower Republican River Basin in Kansas to demonstrate the effects of climate scenarios and water management strategies on water shortages and sediment loads. Results indicate water shortage varies most under different water management strategies, whereas fluvial erosion varies most under different climate scenarios. Fluvial erosion results are highly sensitive to streambank parameters, demonstrating the importance of measuring these parameters and quantifying their uncertainty. This novel modeling approach provides a computationally efficient method of estimating both water shortages and sediment load within one framework and demonstrates the benefit of considering water shortages and fluvial erosion when making water management decisions. [ABSTRACT FROM AUTHOR]

Long-term reservoir management often uses bounds on the reservoir level, between which the operator can work. However, these bounds are not always kept up-to-date with the latest knowledge about the reservoir drainage area, and thus become obsolete. The main difficulty with bounds computation is to correctly take into account the high uncertainty about the inflows to the reservoir. In this article, we propose a methodology to derive minimum bounds while providing formal guarantees about the quality of the obtained solutions. The uncertainty is embedded using either stochastic or robust programming in a model-predictive-control framework. We compare the two paradigms to the existing solution for a case study and find that the obtained solutions vary substantially. By combining the stochastic and the robust approaches, we also assign a confidence level to the solutions obtained by stochastic programming. The proposed methodology is found to be both efficient and easy to implement. It relies on sound mathematical principles, ensuring that a global optimum is reached in all cases. [ABSTRACT FROM AUTHOR]

Reservoirs play a strategic role in the rapid monetary growth of the world by providing numerous benefits. However, the reduction in appropriate sites along with environmental and social apprehensions has resulted in curtailment of new reservoirs around the world in twenty-first century. There is a potential of benefits available from existing reservoirs which can be best capitalized through their optimized operation. Reservoirs Operation Optimization considering Sediment Evacuation (RESOOSE), recently developed model which combines multiple reservoirs operation and sediment evacuation with Genetic Algorithm based optimization module, has been used in the study. The objective of the study was to optimize the irrigation deficit through cascade reservoirs with consideration to hydropower, sediment evacuation and flood damages reduction benefits. The RESOOSE model was applied to optimize the irrigation deficits of Tarbela and Diamer Basha Reservoirs in Pakistan using developed objective function. The article computed and compared the benefits of optimized and existing rule curves. The hydropower benefits of 36.92 Billion Kw, sediment evacuation benefits of 21.534 Million m3 and flood damages of 616.19 Million US$ due to existing rule curves were considered as minimum benefits for achieving the optimized rule curves to minimize irrigation deficits. The developed optimized rule curves reduced the irrigation shortages of case study reservoirs from 6.9 to 5.8 Billion m3 (16% enhancement) annually as compared to existing rule curves. The optimized rule curves minimized the irrigation deficits by maintaining the existing benefits and without lowering the minimum operating levels of case study reservoirs. The study suggests change in existing rule curves of Tarbela and Diamer Basha Reservoirs due to less irrigation shortages. The RESOOSE model can be applied to other cascade reservoirs for optimizing the rule curves. [ABSTRACT FROM AUTHOR]

In river catchments, sediment fluxes facilitate the transport of nutrients and pollutants and reduce water quality, potentially impacting water body health and altering ecosystem functioning. Sediment transport processes also modify the morphology of catchments, and sediment deposition can reduce flow capacity in rivers and water storage capacity in reservoirs and lakes. In this paper, estimates of suspended sediment yields and concentrations in the South Saskatchewan River catchment located in western Canada are presented. The results stem from a SPARROW model, which indicates that the dominant sources of sediment are represented by agricultural fields and urbanized lands. Analyses of sediment retention in the major catchment reservoirs indicate that, as expected, reservoir storage capacity is negatively correlated with reservoir storage reduction and positively correlated with retention rate. Additionally, reservoir lifespans range from less than 100 years to over 9000 years. The results presented here will be useful to complement local environmental guidelines to allow better management of sediment erosion and deposition in the South Saskatchewan River catchment. [ABSTRACT FROM AUTHOR]

Sediment flushing in many reservoirs of the world is accomplished with low efficiency. In this study, a new configuration was proposed for reservoir bottom outlet to increase the pressurized flushing efficiency. In the new configuration, a projecting semi-circular structure was connected to the upstream edge of bottom outlet. It was observed that by employing the projecting bottom outlet, the sediment removal efficiency increased significantly compared to the flushing via typical bottom outlet. In the case of new-configuration bottom outlet with L /D = 5.26 and D /D = 1.32, the dimensionless length, width and depth of flushing cone increased 280%, 45% and 14%, respectively, compared to the reference test. The proposed structure can ensure the sustainable use of reservoirs. [ABSTRACT FROM AUTHOR]

Freshwater reservoirs are under threat because of huge amounts of sediments deposited annually. Sediment flushing seems to be effective to preserve reservoir storage, but it may have negative environmental impacts on downstream ecosystems such as fish mortality. Therefore, providing a suitable flushing strategy that could be compatible with the river ecosystem downstream is of great importance. Two numerical models were developed in this paper to predict the suspended sediment concentration (SSC) on the reservoir-river system and effects of different flushing scenarios on aquatic life. Developed models were applied to the Dez Resevoir system in the southwest of Iran which has suffered from the sediment problems in two last decades. The suitable values for flushing time, concentration limits, and flushing discharge have been recommended in this research by use of the existing information and previous flushing records, as well as field measurement and modeling. Based on social, environmental and technical limitations, March is the appropriate time for flushing. After hydraulic simulation of different flushing scenarios and sediment routing along the river, flushing with 1275 and 800 cubic meter per second with 30 and 20 g per lit concentration in dry and wet season respectively are feasible and have minimum environmental impacts. [ABSTRACT FROM AUTHOR]

Environmental impact assessments (EIA) identify the type, importance, and severity of the environmental consequences of human activities. This study performs an EIA of the Shahriar dam irrigation project in Iran. Physical, biological, and social-economic-cultural criteria and parameters are evaluated in the short and long terms with the Leopold matrix method. Results show that short-term project implementation has its most negative impact in the biological realm (with a score of −48), while long-term implementation would impact most favorably the social-economic-cultural component (+233). A sensitivity analysis of the EIA was employed to determine the relative impacts of the physical, biological, and social-economic-cultural components of the Shahriar irrigation project. [ABSTRACT FROM AUTHOR]

Sedimentation and erosion can significantly affect the performance of river regulated reservoirs. In the vicinity of flow control structures, the interaction between the hydrodynamics and sediment transport often induces complex morphological processes. It is generally very challenging to accurately predict these morphological processes in real applications. Details are given of the refinement and application of a three-dimensional (3-D) layer integrated model to predict the morphological processes in a river regulated reservoir. The model employs an Alternating Direction Implicit finite difference algorithm to solve the mass, momentum and suspended sediment transport conservation equations, and an explicit finite difference scheme for the bed sediment mass conservation equation for calculating bed level changes. The model is verified against experimental data reported in the literature. It is then applied to a scaled physical model of a regulated reservoir, including the associated intakes and sluice gates, to predict the velocity distributions, sediment transport rates and bed level changes in the vicinity of the hydraulic structures. It is found that the velocity distribution near an intake is non-uniform, resulting in a reduction in the suspended sediment flux through the intake and the formation of a sedimentation zone inside the reservoir. [ABSTRACT FROM AUTHOR]

The assessment of the suspended sediment (SS) amount in rivers has an importance because it specifically affects the design and operation of numerous hydraulic structures such as dams, bridges, etc. This paper proposes an adaptive neuro-fuzzy embedded fuzzy c-means clustering (ANFIS-FCM) approach for estimating SS concentration. The accuracy of ANFIS-FCM models was compared with classical ANFIS, artificial neural networks (ANNs) and sediment rating curve (SRC). Daily streamflow and SS data from two stations, Muddy Creek near Vaughn and Muddy Creek at Vaughn, operated by the United States Geological Survey were used in the study. Applied models were compared with each other based on root mean square errors and correlation coefficient. Based on comparison, ANFIS-FCM performed superior to the other two models for modeling complex non-linear behavior of the suspended sediment concentration. The ANFIS-FCM model increased the performance (RMSE) of the optimal MLP model by 10 % and 16 % in estimating SSC for the downstream and upstream stations, separately. ANFIS-FCM model provided improvements in performance and parsimonious and took lesser time in calibration than the classical ANFIS model. [ABSTRACT FROM AUTHOR]

To identify the changing characteristics of runoff and climate change trends and their relationship in the Three-River Headwaters Region (TRHR), this study uses the runoff and meteorological data of three hydrological gauging stations and 12 meteorological stations across the TRHR for the period from January 1960 to December 2009 as the research subjects. The runoff coefficient (RC), ratio of monthly maximum/minimum runoff, and flow duration curves (FDCs) were calculated to identify spatio-temporal variations in runoff and reflect the change in hydrological regime. Results showed an insignificant decrease in annual runoff both in the Yellow River Headwater Region (YERHR) and the Lantsang River Headwater Region (LARHR), whereas it increased in the Yangtze River Headwater Region (YARHR). The RC of the three sub-regions showed a decreasing trend, the LARHR maintained a high mean value of 0.55, followed by a lower value in the YERHR (0.32), and that in the YARHR was the lowest at only 0.23. The variations in monthly maximum/minimum runoff were synchronized; their ratios were relatively steady in the study period. The flow duration analysis showed a remarkable decline in high runoff (at a frequency of 5-15%) in the three sub-regions after 1990. The runoff characteristics showed an overall decrease in the YERHR, the moderate runoff (at the frequency of 15-30% and 40-70%) of the YARHR showed an obviously increase, and the runoff of the LARHR was relatively steady. The relationship between precipitation, temperature and runoff illustrated that precipitation was the dominant factor in runoff generation, whereas the impacts of temperature on regional hydrological regime should not be neglected. Results of this study are of practical significance for water resources management and evaluation of the impacts of climatic change on the hydrological regime in a long-term consideration. [ABSTRACT FROM AUTHOR]

The catchments of the Klang and Ampang Rivers are two sub-catchments that drain into the main Klang River, Selangor, Malaysia. Due to the development and siltation processes, the current capacity of the Klang River in the city centre is insufficient for accommodating the excess flood flow during major events, and, therefore overflows the riverbanks causing flash floods to occur in the Kuala Lumpur city centre. This study investigates the relationship between the rainfall, discharge and suspended sediment transport and its variations during the dry and wet periods in tropical sub-catchments; identifies the different hysteresis types of single flood events in the suspended sediment concentration/discharge relationships in the dry and wet periods, and determines the relationship between the types of single event hysteresis loops and the hydrological and sediment responses. Principal component analysis was performed to examine factors that have a major influence on the suspended sediment yields during both the dry and wet periods. The clockwise and counter-clockwise hysteresis loops occurring mostly during the dry period, can be described as events with moderate total rainfall, rainfall intensity (less than 10 mmh), average discharge and suspended sediment load. Counter-clockwise events occurring during the wet period are associated with low total rainfall, rainfall intensity, average discharge and suspended sediment load. The clockwise and counter-clockwise events that occurred in the wet period are related to events with a relatively high and low moisture condition, respectively. The figure-eight and complex hysteresis loop events occur predominantly during the wet period. The complex loop events occurred mostly during the wet period generates the highest suspended sediment load. The complex loop events occur mostly during the wet period generated the highest suspended sediment load. [ABSTRACT FROM AUTHOR]

Assessing suspended sediment loads in rivers is important since it affects water quality, hydraulic-facility design, and many other sediment-induced problems. Sediment-load estimation heavily depends upon empirical approaches such as a sediment rating curve, which is the empirical relationship between sediment load and river discharge. However, the sediment rating curve is insufficient to describe the inevitable scatter between sediment and discharge. This study aims to develop a probabilistic estimation scheme for daily and annual suspended sediment loads using quantile regression. All recorded daily suspended sediment load and discharge data are employed to construct quantile-dependent sediment rating curves. The empirical probability distribution of daily suspended sediment load is then built by integrating the conditional estimations associated with the corresponding quantiles for a given discharge. The probability distribution of a cumulative sediment load over a longer period can also be derived by the obtained daily sediment-load probability distributions and convolution theorem. The proposed approach is applied to the Laonung station located in southern Taiwan. The results indicate that the proposed approach provides not only the probabilistic description for daily and annual suspended sediment loads, but also the single estimations including the mean, median, and mode of the derived probability distribution. For the 1,110 recorded data of Laonung station during the 1959-2008 period, the proposed mean and median estimation schemes outperform the traditional sediment-rating-curve approach for less mean absolute errors. [ABSTRACT FROM AUTHOR]

The paper develops a new methodology and RESOOSE model for optimizing operation of multiple reservoirs considering sediment evacuation for multiple objectives consisting of maximization of irrigation, hydropower, storage conservation and minimization of flood damages. The optimization and sediment evacuation modules of the model are based on Genetic Algorithm and Tsinghua equation respectively. According to the criteria developed for selection of reservoirs, three reservoirs on Indus River of Pakistan have been selected. The model has been calibrated and validated for Tarbela and Chashma Reservoirs. The calibrated model has been applied to Diamer Basha (proposed) and Tarbela Reservoirs. Eight scenarios comprising of combined and individual objectives were developed. The optimized results of different scenarios have been compared with existing rule curves. The optimization results reveal that objective function for hydropower, irrigation, and storage conservation benefits would be enhanced by 11, 13 and 84 % respectively while flood damages would reduce by 80 %. Similarly the optimized rule curves will increase the benefits up to 579, 960, 533 and 648 million US$ per year (on 2012 prices) for all the four components respectively. The maximum value of US$ 977 million per year has been found for the scenario 5 which gives equal priority weight to all the four sectors. The developed model can be applied to other two reservoirs (in series) for optimization of rule curves. [ABSTRACT FROM AUTHOR]

Soil erosion is the worldwide most significant threat leading to land degradation and water resources deterioration. Identification and prioritization of critical erosion prone areas is an important consideration for policy makers to implement best management strategies that are more sustainable in future for long term use of these natural resources. The present study focuses to identify the specific erosion prone areas within the watershed with the help of hydrological modeling. SWAT model has been used for the identification of critical erosion areas in the Damodar catchment at two levels: watershed and hydrological response unit (HRUs). The derived spatial prioritization maps at watershed and HRUs level indicated that prioritization at watershed scale is not-sufficient methodology for prioritizing the critical soil erosion regions. The critical area identification and prioritization at HRUs level may be more efficient option to achieve the objective of soil erosion control for the policy makers. The HRUs level based analysis showed that about 67.51 % area of Damodar catchment is under critical erosion condition within which a combination of sandy loam soil with agriculture and wasteland landuse is more prone to soil erosion. The results of this study also indicate that erosion is quite sensitive to landuse and soil type within the watershed with other factor of topography and must be utilize to identify the specific patches for an effective soil erosion management rather than planning of whole watershed management which may be a cost intensive option. [ABSTRACT FROM AUTHOR]

Modeling sediment load is a significant factor in water resources engineering as it affects directly the design and management of water resources. In this study, artificial neural networks (ANNs) are employed to estimate the daily sediment load. Two different ANN algorithms, the feed forward neural network (FFNN) and radial basis function (RBF) have been used for this purpose. The neural networks are trained and tested using daily sediment and flow data from Rantau Panjang station on Johor River. The results show that combining flow data with sediment load data gives an accurate model to predict sediment load. The comparison of the results indicate that the FFNN model has superior performance than the RB model in estimating daily sediment load. [ABSTRACT FROM AUTHOR]

The Water Availability Modeling (WAM) System created and maintained by the Texas Commission on Environmental Quality (TCEQ) and its partner agencies and contractors consists of the generalized Water Rights Analysis Package (WRAP) developed at Texas A & M University, which may be applied anywhere in the world, and WRAP input datasets for the 23 river basins of Texas. WRAP is designed for assessing river/reservoir system reliabilities in meeting water supply, hydroelectric power, environmental flow, flood control, and reservoir storage needs. The Texas WAM System supports regional and statewide planning, administration of water allocation systems, and other water resources management endeavors. Activities of numerous water management entities operating 3,435 reservoirs and other facilities in accordance with treaties between the United States and Mexico, five interstate compacts, two water right permit systems with 6,000 active permits, and other institutional arrangements are simulated. The modeling system contributes greatly to water management in Texas and continues to be expanded to address additional water management issues. The Texas experience in implementing the WAM System illustrates key aspects of evaluating water availability from institutional as well as hydrologic perspectives. [ABSTRACT FROM AUTHOR]

Construction of river diversion barrages produces a shallow reservoir, called the pond, which is used more often for flow balancing between the inflows of the river and the outflows of the off-taking canal. However, deposition of sediment in the pond due to the relatively low velocities reduces the pond capacity. The current study investigates the effectiveness of gate operation and variations of other parameters in flushing out these sediment mounds, or shoals, from the barrage pond. Data from laboratory experiments on a scaled model of a prototype barrage is used to train and test different Artificial Neural Network (ANN) models of the system. The models map the relationship between flushing efficiency of a sediment shoal from the upstream of a barrage, and the parameters river discharge, barrage pond depth and area of gate opening, position of the sediment shoal with respect to the barrage. The ANN models are then used to study the effect of different parameters on the sediment flushing efficiency. Apart from river discharge and net area of gate opening, upstream pond depth is also found to have a significant effect on flushing efficiency, with a general trend of decrease in efficiency with increase in pond depth becoming apparent. Efficacy of different gate opening pattern is also tested, with the 'inverted arch' gate opening pattern proving to be the most efficient when compared with 'arch' and 'uniform' gate opening. [ABSTRACT FROM AUTHOR]

This paper presents a multi-objective optimization model for the coordinated regulation of flow and sediment in cascade reservoirs. The model was developed to address two contradicting issues: sediment trapping and flow regulation. The benefits of flood control, hydropower generation and navigation, and sedimentation in cascade reservoirs were considered as the target functions; then the corresponding submodels for reservoir operation and sediment computation were established. The model was implemented by reducing it to a single objective nonlinear model using the constraint method. Non-inferior solutions were obtained by solving the model with catfish effect particle swarm optimization algorithm. The model was applied to the cascade system of Xiluodu and Xiangjiaba reservoirs in the lower Jinsha River in the flood recession period. Under the safety of flood control and navigation, a non-inferior set for impounding time, power generation, and siltation-loss rate of capacity was obtained and optimal solutions with different weights were derived. The results demonstrate that the model is a useful tool in coordinated operations of cascade reservoirs. [ABSTRACT FROM AUTHOR]

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant's principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels. [ABSTRACT FROM AUTHOR]

An attempt is made to develop an integrated system model for the structure of water resources development and management system. The system consists of five subsystems such as watershed management, groundwater development, surface water management, field level development and climate change along with interactions between them. The system is first modelled in the form of hierarchical tree and integrative block diagram for better understanding and analysis. Graph theoretic and matrix models are then developed for storage, retrieval and computer processing. Variable permanent matrix model and variable permanent function in the form of multinomial are the structural models of the system and characterize the water resources development and management system conclusively. Permanent function presents a powerful and exhaustive analysis procedure to generate alternate solutions for the decision makers for the benefit of stakeholders. Coefficient of similarity and dissimilarity are useful matrix for comparing different solutions. SWOT analysis is proposed before taking final and optimum decision on different issues related to water resources development and management system. An illustrative example of groundwater development subsystem is taken to demonstrate the application of methodology. [ABSTRACT FROM AUTHOR]

Land and water degradation due to on-site soil/nutrient loss and off-site pollution/sedimentation are serious environmental problems. Landscape planning and management tools are essential to implement best management practices targeted at locations where they are needed most. Although many soil/water-landscape studies have been published in the last 2 decades, progress in developing operational tools for supporting landscape planning to minimize land and water degradation in developing regions is still modest. Some of the existing tools are data demanding and/or complicated to be useful to data scarce regions. Some require detailed understanding of the hydrological and modelling processes and thus less applicable to local stakeholders involved in land use planning and management. A user-friendly LAndscape Planning and MAnagement Tool (LAPMAT) developed to facilitate land management decision-making. LAPMAT is a menu-oriented interactive graphical user interface that can aid decision makers identify hotspot areas of soil erosion and evaluate the effects of alternative land use management practices at a catchment scale. The modelling framework and its interfaces are designed to guide the user through a series of menus that: 1) allow input model parameters, adjusting coefficients, visualizing input parameters and executing the model; 2) enable changing land use and management practices and re-evaluating potential consequences; 3) allow viewing results in tabular, graphical or map form side-by-side; and 4) (re)-evaluating the respective impacts of management/conservation options. The framework has been applied to assess the severity of soil erosion and simulate the impact of different land management practices using the Revised Universal Soil Loss Equation (RUSLE) adjusted for sediment delivery ratio in an example catchment of northern Ethiopia. The results showed average sediment yield rate of 55 t ha y. Conservation measures targeted at high soil loss areas and gullies gave the maximum reduction in sediment yield by about 80 %. Since LAPMAT allows users handle the selection of management/planning options and provide fast and responsive outputs, it can assist in effective multi-stakeholder negotiations over land-use planning where the minimization of land/water degradation is the ultimate goal. [ABSTRACT FROM AUTHOR]

Understanding temporal variability in water quality in the Three Gorges Reservoir (TGR) is crucial for evaluating environmental effects of damming and protecting China's largest freshwater resource. This study examined water quality changes in the main channel of the Yangtze River after dam completion as well as its relationship with water level fluctuation (WLF), controlled by annual impoundment operations and conditioned by flooding. Finally, the mass balance budget and integrative water quality indexing (WQI) methods were applied to elucidate the status of overall water quality since dam completion. Results showed that TGR outlet water (Yichang) exhibited higher pH and COD values and lower concentrations of dissolved oxygen (DO) and ammonia nitrogen (NH-N) than inlet water (Zhutuo). Temporal variations in water quality parameters displayed similar trends for the outlet and inlet. Water quality parameters all showed negative correlations to water level, revealing the different effects of damming on water quality. It was estimated that reservoir impoundment led to a DO depletion of 1495.5 (±1482.0) × 10 tons/yr and a COD increase of 564.0 (±405.0) × 10 tons/yr, likely deriving from various internal pollutant loads from the WLF zone and tributary watersheds. According to WQI, TGR water quality remained at healthy levels. However, WQI linear regression showed that water quality at the outlet significantly decreased over time, indicating that the construction of the Three Gorges Dam generally caused water quality deterioration. Further investigation is required to determine the spatial distribution of point and non-point pollution sources and to identify major factors that influence TGR water quality. [ABSTRACT FROM AUTHOR]

This study demonstrates an application of uncertainty analysis in evaluating methods of discharge measurement including: the velocity-area, rating curve and efficient methods based on the probabilistic velocity distribution equation. The measurement of river discharge plays a large part in the distribution of water resources. The conventional methods of discharge measurement are costly, time-consuming, and dangerous. Therefore the efficient method of discharge measurement which bases on the relationship between maximum and mean velocities being constant was employed to justify its alternative for the conventional methods: velocity-area and rating curve methods. Distribution test was applied to investigate the statistical properties of the uncertainties involved in the three methods of discharge measurement. Latin hypercube sampling (LHS) method was employed accordingly to assess the discharge features of the three methods of discharge measurement. The main purpose of this study is to quantify the uncertainty involved in several discharge measurement methods and justify the availability and reliability of using the efficient method as an alternative of the conventional methods. Results show that the correlation analysis also validates that the efficient method is a more reliable method than the rating curve method to yield accurate discharge measurements. Moreover, it also yielded comparably accurate measurements as those by the velocity-area method. [ABSTRACT FROM AUTHOR]

Estimation of suspended sediment discharge in rivers has a vital role in dealing with water resources problems and hydraulic structures. In this study, a Multilayer Perceptron (MLP) feed forward neural network with four different training algorithms was used to predict the suspended sediment discharge of a river (Pari River at Silibin) in Peninsular Malaysia. The training algorithms are Gradient Descent (GD), Gradient Descent with Momentum (GDM), Scaled Conjugate Gradient (SCG), and Levenberg Marquardt (LM). Different statistical measures, time of convergence and number of epochs to reach the required accuracy were used to evaluate the performance of training algorithms. The analysis showed that SCG and LM performed better than GD and GDM. While the performance of the superior algorithms (i.e., SCG and LM) is similar, LM required considerably shorter time of convergence. It was concluded that both training algorithms SCG and LM could be recommended for suspended sediment prediction using MLP networks. However, LM was the faster (1/7 of SCG convergence time) of the two algorithms. [ABSTRACT FROM AUTHOR]

Reservoirs are the key infrastructure for the socio-economic development of a country. The reservoirs are proven to be a remedial solution of highly erratic spatial and temporal availability of water. The growth in population and consequent developmental activities within a catchment area has shown to aggravate the problem of sedimentation which comprised of erosion, sediment transport and its deposition in these reservoirs. Among all above mentioned, reservoir sediment deposition is most important as it reduces its useful life and impairs the purposes of these vast water resource. The sediment yield has been considered as comprehensive index for assessing sustainability of such resources. The present study investigates the suitability of Pacific Southwest Inter-Agency Committee (PSIAC) model in determining the sediment yield rate for a drainage basin considering nine basin factors in geographical information system (GIS) environment. For the analysis, a large river basin at the foothill of Himalayas in India has been considered as case study. It was realized that the GIS approach made large basin characteristic sampling very easy and efficient for this hilly basin. A regression equation between specific sediment yield and effective model factors was established based on geomorphic features for this basin. It was observed that most of the basin area is falling under moderate to high sediment yielding potential zone, leading to high sediment yield. [ABSTRACT FROM AUTHOR]

Nestos River flows through Bulgaria and Greece and discharges into the North Aegean Sea. Its total catchment area is around 6,200 km, while the mean annual precipitation and runoff are 680 mm and 40 m/s, respectively. The Hellenic part of the catchment has undergone a substantial hydroelectric development, since two dams associated with major hydropower pumped-storage facilities are in operation. The main objective of the paper is to assess the expected sediment delivery of Nestos R. at the uppermost Thisavros reservoir site. This has been carried out by implementing the Universal Soil Loss Equation in a GIS environment for determining the mean annual soil erosion in conjunction with a suspended sediment measurement program (114 measurements in total) accomplished between 1965 and 1983 adjacent to the dam site. The sediment discharge rating curve between sediment and river discharges in a power form has been constructed using five alternative techniques, namely (a) the linear regression of the log-transformed variables, (b) the same as (a) but with the Ferguson correction, (c) different ratings for the dry and wet seasons of the year, (d) the nonlinear regression, and (e) the broken line interpolation that utilizes different rating parameters for two discharge classes. It is shown that the mean annual sediment yield is almost equal for all rating curve formulations and varies between 178.5 t km and 203.4 t km and the highest value results from the broken line interpolation method. Accordingly, the sediment delivery ratios vary slightly between 17% and 19% of the upstream soil erosion. [ABSTRACT FROM AUTHOR]

Natural hazards such as flooding can cause changes in land-cover. The present study deals with the changes in land-cover in three worst affected districts (Anand, Vadodara and Kheda) of Gujarat state in India due to severe flood during 2005. The Indian Remote Sensing (IRS) P6 Linear Imaging Self Scanning (LISS) III satellite imageries of pre- and post-flooding periods were used as sources of information for the study area. Three classification approaches (unsupervised ISODATA, supervised Maximum Likelihood Classifier, and fuzzy rule based) were used to extract flood induced land-cover information. Results obtained from the above classification approaches were compared. Soft computing technique such as fuzzy based image classification gave better separability amongst classes as compared to hard classification techniques. The accuracy assessment showed that the fuzzy approach can predict land-cover more accurately than traditional approach and also showed great potential for dealing with mapping of flood induced land-cover. Unsupervised classification results for the period October 2004 to October 2005 revealed decrease in inland water bodies (14.49%) and agricultural area (6.42%) while increase in remaining land-cover. During February 2005 to February 2006, all land-cover classes decreased except agricultural fallow and sparse vegetation. In case of supervised classification, decreasing trend was observed only in case of agricultural area (6.78%) during October 2004 to October 2005. Similarly, during February 2005 to February 2006, increase in coastal water bodies (0.73%) and sparse vegetation (1.7%) was observed where as decreasing trend was noticed in the remaining land-cover classes. In fuzzy based classification, only decrease in agricultural area (7.09%) was observed from October 2004 to October 2005, whereas during February 2005 to February 2006, decrease in area was exhibited in all land-cover classes except coastal water bodies and sparse vegetation. Change detection indicated interchange of areas between inland and coastal water bodies and decrease in agricultural area leading to increase in area of agricultural fallow and sparse vegetation. [ABSTRACT FROM AUTHOR]