Geomorphic response of rivers below dams by sediment replenishment technique

River morphodynamics and sediment transportSedimentation in reservoir

Pilot Field Implementation of Suction Dredging for Sustainable Sediment Management of Dam Reservoirs

The buildup of sediment deposits in reservoirs is a long-standing problem with serious consequences on the reservoirs' functionality and the ecology of their river systems. In the last two decades, hydraulic dredging has been used as a more viable engineering solution to restore reservoirs' sustainability. This study proposes a novel ejector-pump dredging system (EPDS) that solely utilizes hydraulic dredging for removal and transport of the sediments deposited at the reservoir's bed. Unlike conventional dredging methods, air is injected into the header pipeline to create a turbulent three-phase flow regime that enhances the solids suspension and continuous flow in the system. Introducing air effectively reduces the critical value of the deposition velocity of the dredged solids and transports them in a slug flow regime. This technique minimizes the tendency of the sediment to settle, and therefore eliminates system plugging. A laboratory prototype of the proposed system has proven the efficacy of removal and transport of mixed-size sediments up to 150 mm. Field trials have further shown the feasibility of the proposed system. Removal of large sediments with productivity approaching 70 m³/h was made possible using the suction-type EPDS. The hopper-type EPDS enabled carrying the dredged material for up to 1, 000 m without resorting to a booster pump. The developed system was successfully used as part of an integrated dredging management program carried out for the Oouchibaru, Saigo, and Yamasubaru dams in the Mimi River basin, Japan. The very low turbidity levels recorded during the sediment dredging and transport operations of EPDS are indicative of the eco-friendly performance of the system

Reconstructing Daily Discharge in a Megadelta Using Machine Learning Techniques

In this study, six machine learning (ML) models, namely, random forest (RF), Gaussian process regression (GPR), support vector regression (SVR), decision tree (DT), least squares support vector machine (LSSVM), and multivariate adaptive regression spline (MARS) models, were employed to reconstruct the missing daily-averaged discharge in a mega-delta from 1980 to 2015 using upstream-downstream multi-station data. The performance and accuracy of each ML model were assessed and compared with the stage-discharge rating curves (RCs) using four statistical indicators, Taylor diagrams, violin plots, scatter plots, time-series plots, and heatmaps. Model input selection was performed using mutual information and correlation coefficient methods after three data pre-processing steps: normalization, Fourier series fitting, and first-order differencing. The results showed that the ML models are superior to their RC counterparts, and MARS and RF are the most reliable algorithms, although MARS achieves marginally better performance than RF. Compared to RC, MARS and RF reduced the root mean square error (RMSE) by 135% and 141% and the mean absolute error by 194% and 179%, respectively, using year-round data. However, the performance of MARS and RF developed for the climbing (wet season) and recession (dry season) limbs separately worsened slightly compared to that developed using the year-round data. Specifically, the RMSE of MARS and RF in the falling limb was 856 and 1, 040 m3/s, respectively, while that obtained using the year-round data was 768 and 789 m3/s, respectively. In this study, the DT model is not recommended, while the GPR and SVR models provide acceptable results

An integrated assessment approach for fossil groundwater quality and crop water requirements in the El-Kharga Oasis, Western Desert, Egypt

Study region: The El-Kharga Oasis in the Western Desert of Egypt is selected as the study area due to its hyberarid climate condition and water scarcity. In this region, the fossil groundwater is the main water source; therefore, preserving groundwater quality and quantity is mandatory. Study focus: This study evaluated groundwater suitability for irrigation purposes and assessed the water requirements of cultivated crops to optimize the water supply in hyperarid climate regions. In total, 79 deep groundwater samples were hydrochemically tested to determine the suitability for irrigation by assessing the key water quality parameters. Spatial distribution maps of all chemical parameters, such as pH, EC, SAR, RSC, SSP, TDS, total hardness, Na+, K+, Ca++, Mg++, Fe, Mn, Cl-, and SO4—, were developed. The FAO CROPWAT 8.0 model, based on the Penman–Monteith equation, was used to forecast agricultural water requirements for three years, 2010, 2011, and 2012. New hydrological insights for the region: The groundwater had medium salinity and low sodium in 84% of the cases. In comparison, high salinity was found in 16% of the samples, indicating that groundwater can be used for many soil types with a low risk of exchangeable sodium. Except for 15 of the 79 wells, all groundwater samples had chloride concentrations less than 100 mg/l. The sulfate ion distribution map showed a low sulfate ion content in the extreme western south. The total annual irrigation water requirements of all crops for 2010, 2011 and 2012 were 199.4, 215.1, and 231.7 million m3/year, respectively, reflecting a gradual increase of approximately 16.57 million m3/total area/year due to the expansion of the cultivated area. The analysis showed that modern irrigation systems reduced the amount of irrigation water by 32% and increased the cultivated area by 45% compared to conventional irrigation methods. Severe groundwater depletion occurred during the dry season from March to July, which exacerbated the water stress in the study region. The results confirmed that the region is under water stress. Accordingly, water conservation is urgently recommended

日本およびヨーロッパアルプスにおける河川形態および持続可能な貯水池土砂管理計画

ヨーロッパアルプス地域のダム貯水池は，流入河川がもたらす土砂の堆積作用によって，その持続可能性が著しく脅かされている。このような貯水池に対する土砂管理計画を，一般化された基準や方策で記述することはなかなか難しい。本報では，日本とアルプス地域のダムにおける土砂堆積に伴うリスクを定義し，これを適切に計測することを目的としている。特に，総合土砂管理の導入によって，水資源の持続的利用，生物環境の保全，さらには，人間と自然の調和を図るために，健全な河川流域を如何に維持するかが最終的な目的である。土砂管理を成功させるためには，河川マネジメントから根本的に変える必要があり，これには，いくつかの対策の組み合わせにより，ダムを通過する水量と土砂量をバランスさせることが重要である。アルプスの大規模貯水池では，密度流が細粒土砂を高濃度で輸送する現象がしばしば観察され，これを適切に制御することが求められる。Sustainability of Alpine reservoirs is severely threatened by sedimentation resulting from natural geomorphologic processes. Management of sedimentation in Alpine reservoirs cannot be apprehended by a standard generalized rule or procedure. The paper aims at identifying, measuring technique to assess the risk of reservoir siltation with and without countermeasures in Japanese and European Alps. Furthermore, analyzing how human interventions and climate changes may alter sediment fluxes, morphological patterns and in river basin system. Maintaining the "Healthy Life of the River Basin" is the ultimate goal of the paper by applies integrated sediment management, to realize the sustainable utilization of water resources and ecological environment protection, and achieve harmony between humans and nature. The results show that, the successful reservoir sediment management proceeds from a permanent change in river management. This may involve strategies to enhance water and sediment release by a combination of several countermeasures. In big Alpine reservoirs, turbidity currents are often the governing process in reservoir sedimentation by transporting fine materials in high concentrations.ヨーロッパアルプス地域のダム貯水池は，流入河川がもたらす土砂の堆積作用によって，その持続可能性が著しく脅かされている。このような貯水池に対する土砂管理計画を，一般化された基準や方策で記述することはなかなか難しい。本報では，日本とアルプス地域のダムにおける土砂堆積に伴うリスクを定義し，これを適切に計測することを目的としている。特に，総合土砂管理の導入によって，水資源の持続的利用，生物環境の保全，さらには，人間と自然の調和を図るために，健全な河川流域を如何に維持するかが最終的な目的である。土砂管理を成功させるためには，河川マネジメントから根本的に変える必要があり，これには，いくつかの対策の組み合わせにより，ダムを通過する水量と土砂量をバランスさせることが重要である。アルプスの大規模貯水池では，密度流が細粒土砂を高濃度で輸送する現象がしばしば観察され，これを適切に制御することが求められる。Sustainability of Alpine reservoirs is severely threatened by sedimentation resulting from natural geomorphologic processes. Management of sedimentation in Alpine reservoirs cannot be apprehended by a standard generalized rule or procedure. The paper aims at identifying, measuring technique to assess the risk of reservoir siltation with and without countermeasures in Japanese and European Alps. Furthermore, analyzing how human interventions and climate changes may alter sediment fluxes, morphological patterns and in river basin system. Maintaining the "Healthy Life of the River Basin" is the ultimate goal of the paper by applies integrated sediment management, to realize the sustainable utilization of water resources and ecological environment protection, and achieve harmony between humans and nature. The results show that, the successful reservoir sediment management proceeds from a permanent change in river management. This may involve strategies to enhance water and sediment release by a combination of several countermeasures. In big Alpine reservoirs, turbidity currents are often the governing process in reservoir sedimentation by transporting fine materials in high concentrations

Reservoir Sedimentation in Wadi Flash Floods Mitigation Structures

The Second International Symposium on Flash Floods in Wadi Systems: 25-27 October 2016. Technische Universität Berlin, Campus El Gouna, Egypt

Flow in shallow rectangular basins: experimental study and 2D numerical simulations

peer reviewe

Integrated Multidisciplinary Approach for Flash Floods Modelling, Forecasting and Mitigation: The Way Forward to Sustainable Development of Wadi Basins

The Second International Symposium on Flash Floods in Wadi Systems: 25-27 October 2016. Technische Universität Berlin, Campus El Gouna, Egypt