Reservoir Siltation Research Articles

Where have all the sediments gone? Reservoir silting and sedimentary justice in the lower Ebro River

At the intersection of natural and social sciences, interest in river sedimentary fluxes and their alteration by human activities is increasing in the context of general retreat of delta formations. Since the 1950s, the construction of large dams in the main course of rivers has produced, among other impacts, a radical decrease in sedimentary fluxes — a key factor in the worldwide sedimentary crisis. While sediment accumulates in reservoirs, the resulting sediment scarcity downstream contributes to land subsidence and coastal erosion, endangering livelihoods in low lying areas such as river deltas. Focusing on the case of the Ebro River and delta (Spain), this article builds on Katherine Dawson's notion of sedimentary justice to examine the articulation of a social demand to mobilise the sediments trapped in reservoirs to counter delta subsidence and coastal erosion. Using a historical perspective and paying attention to matters of both sediment quantity and quality, we show how this demand has developed hand in hand with the emergence of a scientific interpretation of the Ebro delta's origins that emphasises non-human forces and the importance of sedimentary fluxes before human interferences. Activists have taken up this argument to demand the restoration of sedimentary fluxes, exposing corporate hydropower interests and insisting on the mobilisation of sediment trapped in reservoirs. Overall, by scrutinizing the power relations embedded in the immobilization of river sediments, this article contributes to recent work that integrates the materiality of sediment to the hydrosocial framework of analysis and argues that sedimentary justice provides new avenues to incorporate the non-human world to the literature on environmental and water justice.

Groundwater Flow Model along a Vertical Profile of the Sardas Landfill in Sabiñánigo, Huesca, Spain

Lindane (a harmful contaminant) was produced in Sabiñánigo (Huesca, Spain) and deposited at the Sardas landfill. This site contains a large mass of pollutants, which have an extremely large contamination potential of the Ebre River. The site has undergone numerous human interventions that have modified the natural conditions. The site exhibits complex hydrogeological patterns and has been monitored systematically for a long period of time, and a large amount of geological, hydrological, and hydrogeological data are available. Here, a 2D finite element groundwater flow model along a vertical profile heading east–west along the thalweg of the former gully is presented. The main goal is modelling groundwater flow through the landfill, the Gállego River alluvial aquifer, and its interactions with the Sabiñánigo reservoir. The numerical model confirms the prevailing conceptual hydrogeological model of the site. The main results include: (1) Groundwater flows into the landfill mainly along perimeter ditches, which do not properly drain the surface and subsurface runoff (13.84 m3/d) and from the underlying marly rock (8.84 m3/d); (2) The total landfill leachate outflow towards the alluvial floodplain underneath the front slurry wall through a shallow marl layer is equal to 17 m3/d; (3) The oscillations of the Sabiñánigo reservoir water level produce a tidal effect that results in periodic changes of the hydraulic gradient between the alluvial gravels and the reservoir; (4) Groundwater flows generally from the alluvial aquifer towards the reservoir in an average E–W direction with an average Darcy velocity equal to 5 cm/d. The flow direction, however, changes to W–E when the reservoir level rises suddenly and; (5) The hydrodynamic parameters of the alluvial silts and reservoir silting sediments are crucial in determining the influence radius of the inversion of groundwater flow direction when the reservoir level rises suddenly. Model results enhance the confidence of the conceptual model, provide the basis for detailed specific models of the landfill and the alluvial aquifer, and highlight the importance of considering the tidal effect of the reservoir level oscillations. They also provide valuable information for managing the landfill and its impact on the surrounding groundwater system.

Experimental study on flocculation and sedimentation characteristics of cohesive fine sediment measured using ultrasound in the Pearl River Estuary

Flocculation-settling of cohesive fine sediment is the main cause of sediment deposition and changes in topography and geomorphology in estuaries. However, studies on estuary morphology have often focused on a single influencing factor, and sediment deposition characteristics under disturbances in sediment concentration, moisture content, and external forces have rarely been considered simultaneously. The authors propose an ultrasound-assisted flocculation-settling method to analyze the various factor affecting cohesive sediment. The current study examined the sedimentation patterns of cohesive sediment with a sediment content concentration of 30%–80% through ultrasound experiments. The results show that when the sediment concentration is 40%–50%, the best effect on flocculation and sedimentation is induced by ultrasound waves. The corresponding settling height at the clear-muddy water interface is 3.05–3.45 cm, and the settling rate is 0.161–0.173 cm/min. Finally, using ultrasound waves, a moisture content of the sediment concentration of 30%–80% was analyzed based on wet and dry conditions. Taking a sediment concentration of 50% as an example, the maximum values of the variation in the water contents of the upper, middle, and lower layers of the wet basis were 0.82%, 0.51%, and 0.37%, respectively, whereas those of the upper, middle, and lower layers of the dry basis were 4.77%, 1.07%, and 0.60%, respectively. Thus, the moisture content of dry and wet sediment varied as follows: Wupper > Wmiddle > Wlower. The current research results can provide a theoretical basis and technical reference for siltation in channels, harbors, and reservoirs; the evolution of submarine deltas and coastal beaches; transportation of fluid mud; and the treatment of hyper-concentrated sediment flows.

Study on the coordination of flow and sediment transport, ecological environment, and crop production in the Lower Yellow River since 2000

AbstractThe Xiaolangdi Reservoir has been operated for 23 consecutive years, greatly altering the flow and sediment processes of the Lower Yellow River. Many research have separately analyzed the changes of siltation in reservoirs and river channels, discharge capacity of the lower river channel, river regime stability, or ecological environmental benefits under water and sediment regulation. However, the multiple changes of flow and sediment transport, ecological environment, and social economy were seldom considered. We systematically and holistically explored the changes of river system in the Lower Yellow River since 2000, based on the channel erosion and siltation, channel morphology, ecosystem patterns and habitat quality, irrigation water scale, and crop production index. The results show that the discharge capacity of the main channel has been recovered significantly at a bankfull discharge of over 4700 m3/s. The ecological pattern in the Lower Yellow River and the delta has been optimized. The wetland and water ecosystem area has been remarkably increased by 125.82% and 318.54% respectively, and the saline‐alkali land area has been sharply reduced by 89.65%. The habitat quality has been raised to the highest level in nearly 40 years. The irrigation water volume in the irrigation area of the Lower Yellow River has been increased by 31%, and the grain production has maintained a continuous growth for 16 years. Overall, the coordinated development level of flow and sediment transport, ecological environment and crop production in the Lower Yellow River has been continuously improved from the reluctantly coordinated level (before water and sediment regulation) to the highly coordinated level.

Soil erosion rate and hazard level at the Sianjo-anjo Reservoir watershed in Indonesia

The Sianjo-anjo reservoir is used to meet the need for downstream clean water. Land activity at the Sianjo- anjo reservoir watershed can potentially increase the rate of erosion and the silting of rivers and reservoirs due to sedimentation. Reservoir siltation is a crucial challenge for reservoir management because it can reduce its function and affect its service life. However, sediment yield is often overlooked in reservoir planning and environmental assessment. This study aims to predict the rate of land erosion and sediment yield, and create an erosion hazard map of the Sianjo-anjo reservoir watershed. The study used a Geographic Information System, GIS-based Universal Soil Loss Equation (USLE) method and discovered that the erosion rate of the Sianjo-anjo reservoir watershed was between 35.23 Mg∙ha –1∙y –1 until 455.08 Mg∙ha –1∙y –1, with 95.85% classified as the low level, 0.03% as moderate, and 4.12% as high. Meanwhile, the sediment yield from the Sianjo-anjo reservoir watershed was 218,812.802 Mg∙y –1. USLE is vital to identify areas susceptible to erosion and crucial for reservoir sustainability. Furthermore, it is necessary to plan good sediment management. Long-term land conservation is required to maintain storage capacity and ensure effective operation of the reservoir.

Impact of Sedimentation and Bathymetry of Selected Small Reservoirs on the Priority Water-Linked Sectors in the Zambezi River Basin

This study was conducted within the Zambezi River Basin to ascertain the bathymetry and sedimentation of selected reservoirs, evaluate their seasonal hydrological regimes, pinpoint the causes of reservoir siltation, and determine how the bathymetry and siltation impacted water-related industries and policy choices. Hydrological field measurements using a hydrographic survey boat, document studies, and interviews were used to collect the data. The 3D spatial analyst tools in ArcGIS 10.3 and hypsometric curves were used to analyze bathymetric data. Thematic analysis was used to analyze qualitative interview data. Findings indicated that sedimentation was a problematic phenomenon spatial-temporally and, it triggered a significant decrease in the storage capacities of the reservoirs. The study noted that catchments with small reservoirs were vulnerable to severe water stress, particularly from July through the beginning of the next rainy season in December. Over 90% of the local population and water-related industries were facing substantial risks of economic water shortages and may continue to face more water challenges amidst escalating climatic changes. The problem could be addressed by coping mechanisms such as alternative livelihoods, water harvesting, and water shedding. This study proposes an Integrated Water Resources Management Framework, which may help incorporate water education to bring about behavioural change against drivers of sedimentation. The proposed sediment and water resources management model serves as a multidisciplinary and transdisciplinary tool that could be used to address siltation concerns. This work has also shown the significance of bathymetric surveys of small reservoirs as a basis for policy context and regulations on managing water resources.

Online Control of the Raw Water System of a High-Sediment River Based on Deep Reinforcement Learning

Water supply systems that use rivers with high sedimentation levels may experience issues such as reservoir siltation. The suspended sediment concentration (SSC) of rivers experiences interannual variation and high nonlinearity due to its close relationship with meteorological factors, which increase the mismatch between the river water source and urban water demand. The raw water system scheduling problem is expressed as a reservoir and pump station control problem that involves real-time SSC changes. To lower the SSC of the water intake and lower the pumping station’s energy consumption, a deep reinforcement learning (DRL) model based on SSC prediction was developed. The framework consists of a DRL model, a hydraulic model for simulating the raw water system, and a neural network for predicting river SSC. The framework was tested using data from a Yellow River water withdrawal pumping station in China with an average capacity of 400,000 m3/d. The strategy created in this study can reduce the system energy consumption per unit of water withdrawal by 8.33% and the average annual water withdrawal SSC by 37.01%, when compared to manual strategy. Meanwhile, the deep reinforcement learning algorithm had good response robustness to uncertain imperfect predictive data.

Numerical investigation of submerged impinging jet based on different turbulent models

In today’s world, the loss of effective storage capacity caused by reservoir siltation has reached 50 billion cubic meters per year. As a high impact and simple water jet technology, submerged jet impact can have a powerful washout effect on submerged sediment. On this article, the submerged impinging jet is numerically computed with importing the Wray–Agarwal (W-A) turbulence models in FLUENT. Then, the streaming field analysis of the jet under different conditions is carried out and compared to the PIV test outcomes. To validate the effectiveness of the W-A turbulence models for predicting the streaming field of submerged impinging jet. The results show that, relative to other turbulence models, the calculated findings of the Wray–Agarwal turbulence model are in much closer accordance with the test data.

The Response of Sensitive LULC Changes to Runoff and Sediment Yield in a Semihumid Urban Watershed of the Upper Awash Subbasin Using the SWAT+ Model, Oromia, Ethiopia

Land use and land cover (LULC) changes in many parts of river basins have caused water shortages, flood risks, land degradation, soil loss, biodiversity loss, and ecosystem deterioration. LULC change and topography are the main factors that cause land degradation and soil erosion in the Ethiopian highlands. The aim was to evaluate the rate of the LULC change and its effects on runoff and sediment yield in the semihumid subtropical Awash watershed using the SWAT + model. The land use maps of 2000, 2010, and 2020, along with constant climate data from 1992 to 2020, were used to investigate the effects of LULC dynamics on runoff and sediment yields. Agriculture and urbanization both increased at 7.1% and 7.95%, respectively. In contrast, the forest area decreased by 8.8% and shrubland by 3.25% from 2000 to 2020. Bare soil and urban areas covered the majority of the landscape units that were labeled as potential runoff generators. The majority of the soil erosion-prone areas that were classified as severe in the second and third scenarios covered a sizable area of urban, agricultural, and shrubland. These soil erosion hotspots covered an area of 3,777.3 ha (3.18%) and 13,413.1 ha (11.3%), with a total annual sediment yield of 361.93 m/ton and 1239.24 m/ton, respectively. In general, the change in LULC results in the annual sediment yield, with mean annual amounts of 241.8 tons/ha, 408.7 tons/ha, and 732.4 tons/ha for each scenario in the sequence. The model performance was tested using R2 = 0.88, NSE = 0.9, and PBIAS = −2.36, which indicate good agreement between simulated and observed flow, and R2 = 0.82, NSE = 0.86, and PBIAS = 4.38 for the simulated against recorded sediment yield. The increases in sediment yields have serious implications for reservoir siltation downstream of the watershed and warn land use managers to take action.

Fingerprinting Sediment Origin of the Silting Process of Urban Reservoirs

The silting process of urban reservoirs has been occurring in many regions across the world. However, identifying the main sources of sediment and controlling the silting process in urban reservoirs are still unsolved problems in many regions, mainly in developing countries such as Brazil. In this study, we identify which land use most influences the siltation of reservoirs, and how the different tributary streams contribute to this process in two urban reservoirs located in Campo Grande, Midwestern Brazil. Thus, we applied a sediment source fingerprinting (SSF) approach, associated with land use analysis, and the bathymetric data of reservoirs connected to the stream and drainage network, obtained between the years 2008 and 2018. The reduction in the volume and area of the reservoir during the study period were 45% and 39%, respectively. We found a proportional relationship between the reduction in the reservoir volume and the increase in the impermeable areas of the studied basin. We also noted that the sediments deposited in the reservoir originate from bare soil, banks, and bed in the proportions of 46.9%, 37.1%, and 17.2%, respectively. Our findings show that the use of bathymetric surveys and data on land use and land cover, associated with the source tracing technique, are useful alternatives to identifying sediment mobility in urban basins, especially in those where the drainage network is connected to water courses. We conclude that the factors that most contribute to the silting up of reservoirs are the erosion of banks and beds, sediment remobilization and the connectivity of the drainage network with water courses.

The Kabul River Basin - the source of the Naglu and other reservoirs

The article is devoted to the assessment and study of the Kabul river basin fed by 7 existing (Jabal-Saraj, Karga, Mahipar, Naglu, Sarubi, and Darunta) and numerous planned (including Gulbahor, Baghdara, Sarubi II, Kunar I, Kunar II, Shatut) reservoirs. The article discusses the Kabul basin's annual precipitation, land cover, and runoff. In addition, it sheds light on soil erosion and the concentration of river and reservoir sedimentation in the Kabul River Basin. Recommendations are also given for solving the problem of soil erosion and the siltation of reservoirs. There is very little data on the Kabul River and its basin due to the lack of detailed hydrological data. Most of the hydrological and meteorological posts did not function or were destroyed during the crisis in the country for about two decades, which led to little or no information on the river's hydrology during this period. Because of this problem, many organizations working in basin water management and designing new hydraulic structures face difficulties in properly planning and designing new hydraulic structures and reservoirs. As a result, most researchers, planners, and designers use old data with a limited observation period, which is insufficient for adequate design and planning of hydraulic structures and other basin development projects. Due to four decades of unrest in the country, the watersheds of the Kabul Basin have been used without any rules or management, resulting in land degradation and watershed erosion. Three main problems, namely overgrazing in rangelands, rain-fed fields, and deforestation, have caused land degradation in the basin. In addition, the situation has been aggravated by the cutting of bushes for fuel in hilly and semi-hilly areas. The basin is overpopulated, and there are many industries in the major cities of the basin, which contributes to water pollution in the Kabul river. Despite water availability, due to a lack of proper planning, the major cities in the basin cannot use the basin's water for domestic needs. In cities like Kabul and Jalalabad, people mainly use groundwater, resulting in the continuous sinking of the groundwater level. For the proper management and development of the Kabul river basin, much work needs to be done, which may yield promising results for developing the country's economy and improving the environment in the Kabul basin region.

ОЦІНКА ЗАРЕГУЛЬОВАНОСТІ СТОКУ РІЧКИ СЕРЕТ

The Seret River is a 242 km long left tributary of the Dniester, flowing within the Ternopil region. The basin covers an area of 3900 km2, a river slope of 0,9 and a river network density of 2,44 km2/km. The average long-term water discharge in the river is 12,1 m3/s, the water turbidity is 100-200 g/m3 and the salinity is 350-550 mg/dm3. There are 8 small hydropower plants on the river with a total capacity of 21,57 MW. The aim of the study is to assess the regulated flow of the Seret River and determine the amount of siltation in the reservoirs in its channel. The study found that 8 reservoirs have been created on the Seret River, with a total water surface area of 21 km2 and a total volume of 57,4 million m3. The Seret River is one of the most heavily regulated rivers in the Western Podillia. The Seret River basin contains 30% of all reservoirs in the Ternopil region. The upper reaches of the river are the most regulated, with 5 reservoirs with a total volume of about 33 million m3 and a usable volume of 25 million m3. According to the results of the calculations, it was found that the coefficient of flow regulation of the Seret River is 0,17; the degree of flow regulation is 0,25. The volume weight of sediment in the Seret River is 0,79 t/m3. It was found that the river transports about 57 thousand tonnes of sediment per year. Over the estimated period of operation (40 years), 3 million m3 of sediment will accumulate in the Seret River reservoirs. The siltation of Ternopil reservoir is 3,5 %, Vertelivske – 5 %, Zalozhtsivske – 10 %, Verkhnya Ivachyvka – 58 %, Bilche-Zolotetske – 65 %, Skorodynske – 75 %. Based on the results obtained, it can be concluded that the Seret River is undergoing significant anthropogenic pressure, and there are risks of degradation of the watercourse and a decrease in the energy potential of the reservoirs in the middle and lower reaches of the river. Therefore, there is a need to develop scientifically based measures to optimise nature management and renaturalise the Seret River basin and valley.

Analysis results of data obtained in natural field research in mountain river Sokhsoy

Forecasting and preventing silting of hydraulic structures, irrigation canals, and reservoirs, as well as improving methods for maintaining their throughput, is particularly important. In this regard, special attention is paid to research work aimed at improving hydraulic calculation methods, taking into account the variability of channel factors in the design and construction of hydraulic structures planned for construction. This article analyzes the factors influencing the occurrence of the deformation process in the channels based on the information obtained in the natural field conditions.

Sediment deposition of Three Gorges Reservoir and its impact on the reservoir area in recent 20 years

泥沙问题是三峡工程建设与运行中的关键技术问题之一,只有妥善处理好泥沙问题,才能保证三峡工程长期有效使用,维持水库功能的全面发挥。本文首先结合实测水文、河道地形观测资料,对三峡水库运行近20年来的泥沙淤积特性及水库排沙比进行了较为全面的分析研究,并与已有研究成果进行了对比;其次,围绕防洪、航运以及坝前段的泥沙淤积等方面,进一步分析了水库淤积产生的影响。结果表明:三峡水库蓄水以来,在不考虑区间来沙的情况下,三峡水库共淤积泥沙20.484亿t,近似年均淤积1.102亿t,水库排沙比为23.6%,水库年均淤积量为原论证预测值的33%。其中,库区干流段累计淤积泥沙17.835亿m³(变动回水区冲刷0.694亿m³;常年回水区淤积18.529亿m³),淤积在水库防洪库容内的泥沙为1.648亿m³(干、支流分别淤积1.517亿m³和0.131亿m³),占水库防洪库容的0.74%,“十一五”攻关阶段研究得出的多年平均淤积量及排沙比较实测值均偏大,变动回水区冲淤则出现反向的情况,主要原因是研究采用的入库沙量偏大以及近期河道采砂和水库优化调度等影响。水库淤积对防洪库容和地下电厂的影响尚小,对库区部分水道航道条件产生了一定的影响,应加以关注。;Sediment problem is one key technical issue in the construction and operation of the Three Gorges Project. Only by properly handling the sediment problem can we ensure the long-term effective use of the Three Gorges Project and maintain a full play of the reservoir function. In this paper, the characteristics of sediment deposition and the sediment discharge ratio of the Three Gorges Reservoir (TGR) in the past 20 years have been comprehensively analyzed and studied based on the observed hydrological and river topographic data, and compared with the existing research results; Secondly, the influence of reservoir sedimentation is further analyzed in terms of flood control, navigation and sediment deposition in front of the dam. The results show that since the TGR impoundment, the total sediment deposition of the TGR is 2.0484 billion tons, approximately 110.2 million tons per year, the sediment discharge ratio of the reservoir is 23.6%, and the average annual sediment deposition of the reservoir is 33% of the original demonstration prediction value without considering the sediment from the interval. Among them, the accumulated sediment deposition in the main stream section of the reservoir area is 1.7835 billion m³ (69.4 million m³ scoured by the fluctuating backwater area; 1.8529 billion m³ silted by the perennial backwater area), and the sediment deposition in the reservoir flood control storage capacity is 164.8 million m³ (151.7 million m³ silted by the main stream and 13.1 million m³ silted by the tributary respectively), accounting for 0.74% of the reservoir flood control storage capacity. The average annual sediment deposition and sediment discharge measured during the 11th Five Year Plan period are relatively large, the scouring and silting in the fluctuating backwater area are reversed, mainly due to the influence of the large amount of sediment entering the reservoir, the recent sand mining in the river channel and the optimal operation of the reservoir. The influence of reservoir siltation on flood control storage capacity and underground power plant is still small, and it has a certain impact on some waterway conditions in the reservoir area, which should be paid attention to.

Assessment of sediment yield and deposition in a dry reservoir using field observations, RUSLE and remote sensing: Wadi Assarin, Oman

Soil erosion, sediment yield, and sediment transport associated with flash flooding in arid regions result in reservoir storage losses, decreased infiltration, high evaporation rates, and degradation of downstream channels. However, the lack of observational data from wadi systems and an empirical formula to compute sediment yield has hindered reservoir trapping evaluation, maintenance, and management. Therefore, this research aimed to estimate the annual soil loss in the upstream catchment area of a reservoir based on the Revised Universal Soil Loss Equation (RUSLE) with a remote sensing dataset. The sediment trapped in the Assarin Dam reservoir in Oman was estimated by coupling unmanned aerial vehicle (UAV) surveys with photogrammetry analysis to assess the reservoir siltation. Among the previous sediment trapping events, seven sets of field observation data were collected to investigate the relationship between soil loss at the catchment scale and sediment deposition volumes in the reservoir. The RUSLE method was applied to estimate soil erosion using independent factors such as rainfall erosivity, soil erodibility, topography, cover management and conservation practices. A remote sensing dataset and geographic information system (GIS) environments were used to analyse the quantitative and spatial distribution of the RUSLE parameters. Two drone surveys were conducted over the reservoir before and after a flash flood. The trapped sediment volume was estimated to be approximately 9,075 m3 (11,343 ton) per event, representing approximately 1.26 % of the total reservoir capacity. This computed volume was validated using measurements from monitored sediment scale bars sited throughout the Assarin Dam reservoir, yielding an accuracy of 79 %. From the RUSLE results, the annual soil erosion was estimated to be 196,599 ton/ha yr−1, of which approximately 5.8 % was trapped in the reservoir. Spatial-temporal variability in the rainfall patterns and the corresponding runoff discharges led to high sediment delivery at the outlet of the basin. After analysing available data from previous field surveys in Oman, a new formula for estimating the sediment yield in Wadi Assarin was developed. The results of this research, which represent the first of their type in the Middle East and North Africa (MENA) region, can support reservoir management practices and show that UAV-based photogrammetry is suitable for measuring trapped sediment volumes.

CLIMATE CHANGE, MITIGATION OF FLOODS AND DROUGHTS: ONLINE INFORMATIVE AND EDUCATIONAL RESOURCES

According to projections, in many regions of the world, heavy rains interspersed with long lasting dry periods are to be expected as a consequence of climate change, which requires adaptation strategies. In fact, dry soils have no time to soak heavy rains that fall quickly, the groundwater resources are not replenished and the aquifers are declining. At the same time, flood prone areas may suffer floods. Notoriously, this is already happening. In the meanwhile shrinking glaciers, and dam reservoirs that lose storage capacity as a consequence of sediment accumulation, further limit water availability downstream. In addition, coastal areas deprived of the sediments trapped in the reservoirs, undergo land losses; the Mississippi river delta has already lost 4,800 km², an area roughly the size of Delaware. The siltation of dam reservoirs can be mitigated; in this regard, several techniques are presented. The intensive exploitation of an aquifer, combined with a limited replenishment, may result in, e.g. land subsidence and seawater intrusion. Several techniques aimed at enhancing the recharge of aquifers, harvesting rainwater and saving water are presented in the article. Urban structures, such as rain gardens, bioswales, permeable asphalt and permeable pavements allow rainwater to infiltrate into the soil, thus recharging aquifers and mitigating overland runoff and floods. Several documents presented in the article deal with improving the liveability of cities, increasingly crowded and hot, thanks to a more efficient water management and planting trees. Our dietary choices, the clothes we wear and the food we waste have an influence on the overexploitation of water resources, sometimes in producing countries very far away from our country.<p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/edu_01/0261/a.php" alt="Hit counter" /></p>

Method for calculating the solid runoff of rivers and silting of riverbed reservoirs

The article presents a methodology for calculating the solid runoff of rivers that feed riverbed reservoirs located on the territory of the Republic of Uzbekistan. The dependence of the intensity of silting of riverbed reservoirs on their geographical location and reduced turbidity was obtained. The procedure for determining the volume of silting of reservoirs using the value of the annual solid runoff of the river is given. The advantage of this method for calculating silting in comparison with the methods of other authors is shown.

Water Management causes increment of reservoir silting and reduction of water yield in the semiarid State of Ceará, Brazil

The semiarid State of Ceará, Brazil, implemented its water management system in the early 1990s. The drought-prone State is densely populated and its supply strongly relies on surface reservoirs, whose yield reduces with silting. Using artificial neural networks and data from 141 monitored dams, we show that the silting ratio of the reservoirs significantly enhanced after the implementation of the water management system. An explanation for this fact is that, since the management started, water withdrawal increased, leading to lower reservoir levels at the beginning of the rainy season. This reduces the probability of spilling, which is the main mechanism of sediment outflow, thus causing excessive siltation. As a result, water availability is expected to reduce by 6% in 30 years, creating a clear contradiction with the management objectives. To tackle this problem, four actions are recommended: to include spilling in the operational rules, to reduce erosion in the basins, to execute sediment reuse policy, and to implement water-demand management.

Siltation of Small Water Reservoir under Climate Change: A Case Study from Forested Mountain Landscape of Western Carpathians, Slovakia

The effectiveness of small reservoirs in a mountain landscape continuously decreases over time due to the gradual siltation. We examined two hypotheses about the enhanced siltation rate and the constant relative contribution of unpaved roads to the siltation of a small water reservoir in the period 1990–2014, with pronounced climate change, compared to the reference period 1970–1989. Analysis was based on deposit volumes extracted from the reservoir in 1989 and detected at the reservoir bottom in 2014. The geographical information systems, image analysis and universal soil loss equation were applied to model the soil erosion according to the two sources—catchment area and roads—to study siltation processes in depth. Despite expectations, rates of siltation were almost unchanged in compared periods. The positive changes in vegetation cover (the forest expansion and changes in forest management practices) offset the enlarged rain erosivity. On the other hand, road erosion increased by 41% from 1990 and became twice as much a contributor to sediments compared to 1970–1989. The intensity of erosion from roads was from 13 to 29 times greater than from other areas. Therefore, proper maintenance of road networks could rapidly decrease reservoir siltation. Moreover, we recommend continuous cover forestry as a critical measure for central Europe’s forested regions to prevent growing erosion pressures.

Past and Future Land Use/Land Cover Changes in the Ethiopian Fincha Sub-Basin

The increasing human pressure on African regions is recognizable when looking at Land Use Land Cover (LULC) change maps, generally derived from satellite imagery. Using the Ethiopian Fincha watershed as a case study, the present work focuses on (i) identifying historical LULC change in the period 1989–2019; (ii) estimating LULC in the next thirty years, combining Geographical Information Systems (GIS) with Land Change Modelling (LCM). Landsat 5/8 images were combined with field evidence to map LULC in three reference years (1989, 2004, 2019), while the Multi-Layer Markov Chain (MPL-MC) model of LCM was applied to forecast LULC in 2030, 2040, and 2050. The watershed was classified into six classes: waterbody, grass/swamp, built-up, agriculture; forest; and shrub. The results have shown that, in the past 30 years, the Fincha watershed experienced a reduction in forest and shrubs of about −40% and −13%, respectively, mainly due to ever-increasing agricultural activities, and such a trend is also expected in the future. In fact, for the period 2019–2050, LCM simulated a significant decrease in both forest and shrubs (around −70% and −20%, respectively), in favor of more areas covered by grass (19%) and built-up (20%). It is worth noting that a decrease in natural forests can drive an increase in soil erosion, fostering siltation in the water reservoirs located in the sub-basin. The study pointed out the urgency of taking actions in the sub-basin to counteract such changes, which can eventually lead to a less sustainable environment.