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The Chesapeake Logperch, Percina bimaculata, is a small fish endemic to the upper Chesapeake Bay drainage with a range significantly reduced by water quality and habitat degradation. It was described by Haldeman in 1842 and 1844 from the Susquehanna River, Pennsylvania, synonymized with the Logperch (Percina caprodes) by Jordan in 1877, and redescribed by Near in 2008. It is extirpated from the Potomac River drainage and extant in a portion of its historic range within the Susquehanna River drainage of Pennsylvania and Maryland in the United States of America. We reviewed available historic field survey information and defined the likely extent of the historic distribution of P. bimaculata and its change in response to historic environmental perturbations. We performed fisheries surveys during 2004–2023 to fill data gaps and to define the current distribution and abundance in the Susquehanna River drainage within Pennsylvania. Our surveys utilized electrofishing gears, electrified benthic trawls, and seines. Our surveys targeting P. bimaculata on the Susquehanna River and tributaries from York Haven to Holtwood, Pennsylvania, combined with available fisheries surveys conducted by others, confirm it was extirpated from that portion of the drainage. We documented the continued usage of Conowingo Pond, Susquehanna River, and tributaries below Holtwood by populations known to exist in historic field surveys. These populations appear to have been stable since at least the 1960s based on historic data and our current surveys. We documented previously unknown populations in the Octoraro Creek drainage, Octoraro Reservoir, and Muddy Run Pumped Storage Facility. Habitat utilization observations during our surveys indicate that clean sand, gravel, rubble, boulders, and large woody debris are preferred substrates. In the lower Susquehanna River and two tributaries, P. bimaculata has demonstrated a plasticity of habitat usage by continuing to occur in environments converted into impoundments by dams. In these impoundments, shorelines and connections with clean tributaries containing preferred substrates appear to be important given their utilization by P. bimaculata during our surveys. It is our opinion that the Susquehanna River and tributaries above Holtwood once again constitute suitable habitats. Conservation efforts focused on reintroductions, water quality, habitat, and connectivity have the potential to increase the extent of occurrence, abundance, and security of P. bimaculata. [ABSTRACT FROM AUTHOR]

Dams play a vital role as a primary water supply for irrigation in Jordan, necessitating an assessment of their water quality. This study aimed to evaluate the suitability of irrigation water in a key number of Jordanian dams, namely Al Kafrain, Al Waala, King Talal (KTD), Mujib, Shuaib, and Sharhabil. Monthly readings of major water parameters (EC, Cl−, SO42−, HCO3−, Na+, Ca2+, and Mg2+) were recorded for seven years (2015–2021) for each dam. The assessment criteria included the sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC), magnesium adsorption ratio (MAR), kelley ratio (KR), total hardness (TH), and water quality index (WQI) using both average (APL) and maximum permissible limits (MPL). Additionally, USSL, Wilcox, Doneen, Piper, and Gibbs diagrams were applied. The findings indicate that all the dams demonstrated suitability for irrigation based on the SAR, SSP, RSC, MAR, and KR values. The USSL diagrams showed most samples falling under C2S1 and C3S1, except KTD, which fell under C3S2. According to the Wilcox diagram, the water was either Excellent to Good or Good to Permissible, while the KTD water was classified as Permissible to Doubtful. Furthermore, the water chemistry was found to be mainly influenced by rock weathering, as revealed in the Gibbs diagram, and has no restriction on permeability, according to the Doneen diagram. The WQI showed that all the dams fall in the Good and Excellent category for irrigation using APL, while applying MPL, all the dams were in the Excellent category, which demonstrates the necessity of considering extreme events and regulatory thresholds. [ABSTRACT FROM AUTHOR]

The present study examined temporal variations in water and sediment discharges in the Red River basin from 1958 to 2021 resulting from climate change and anthropogenic factors, with projections extended to 2100. The 64-year observational period was divided into five distinct stages: 1958–1971 (Stage I: natural conditions); 1972–1988 (Stage II: onset of human activities); 1989–2010 (Stage III: post Hoa Binh dam construction); 2011–2016 (Stage IV: series of new dam constructions); and 2017–2021 (Stage V: combined effects of human activities and climate change). Attribution analysis revealed that human activities accounted for 62% and 92% of the dramatic declines in sediment loads in Stages III and IV, respectively. Projection results of fluvial sediment loads over an approximate 150-year timeframe (1958–2100) indicate an overriding impact from human activities. Climate change projections based on four scenarios (−5%, +5%, +10%, and +15% change per year) suggest associated decreases or increases in river flows. This study predicts that projected 21st century increases in river flow attributable to climate change will offset up to eight percent of the human-induced sediment load deficit. [ABSTRACT FROM AUTHOR]

An important aspect of economic considerations is the routing and safety of hydraulic storage facilities such as dams for extreme probable water flooding. The routing of dam reservoirs requires more attention for determining the magnitude of extreme probable flooding. Apparently, the type of structure, importance, and economic development of the surrounding area guide the routing criteria for choosing the extreme flood magnitude. The Maithan and Panchet Dams in India have faced several major floods with diversified magnitudes since 1978. The present study aims to estimate the storage and routing of extreme probable floodings for these two dams based on real-time flood data like inflow, outflow, and elevation for the extreme flood years of 1978, 2009, and 2014. Reservoir storages at different elevations are calculated from the initial storage volumes. For both reservoirs, discharge equations are derived and calculated at given elevations during extreme floods. The Modified Puls technique is used for routing extreme floods. At the end of each extreme flood in 1978, 2009, and 2014, the variation in outflow discharges at different elevations and flood hydrographs is predicted. Finally, estimated outflow discharges are compared with the actual outflow discharges for the given inflows during extreme floods. Using this approach, extreme floods that occurred in 1978 are predicted with less than 10% error. Outcomes from this study may help in the future planning and routing of flood-control detention facilities and in predicting the variation in outflow discharges at different elevations. Based on this work, alternative studies and regional drainage planning can also be carried out. [ABSTRACT FROM AUTHOR]

Pensacola Dam, operated by the Grand River Dam Authority (GRDA), is a multiple-arch buttress dam constructed in 1940. The dam has little or no existing geophysical reports on the integrity of the dam foundation rock and even less knowledge at depth. Visual inspection indicated evidence of seepage at some arches of the dam. As a pilot study, we conducted a suite of geophysical surveys inside two arches (Arch-16 and Arch-17) and a part of the downstream berm to characterize the dam foundation rock, delineate seepage zones, and identify the most appropriate geophysical methods for temporal monitoring of the dam's conditions. The geophysical methods included electrical resistivity tomography (ERT), self-potential (SP), multichannel analysis of surface waves (MASW), compressional (P)-wave refraction, and shear (S)-wave reflection. Water samples were collected for geochemical analysis to investigate the source of the seepage flow inside Arch-16. The geophysical results characterized the dam foundation rock into an unsaturated limestone and chert overlying a water-saturated limestone and chert. The ERT profiles indicated that groundwater is rising inside the arches and significantly dropping under the downstream berm, which can be due to the uplift pressure beneath the dam base. Zones of high seepage potential were detected near the buttress walls of the two surveyed arches, which may be related to previous blasting, excavation of the dam foundation, concrete placement, or improper grouting. The geochemical analysis of water samples taken from the artesian wells inside Arch-16 and the Grand Lake revealed different chemical compositions, suggesting that the source of water could be a mixture of groundwater and lake water or lake water interacting with rock and reaching the surface through fractures; however, more sampling and further analysis are required to ascertain the source of the seeps. This study showed that the ERT, SP, and S-wave reflection methods have effectively characterized the dam foundation rock and seepage zones beneath the arches. The study provided a better understanding of the conditions of the dam foundation rock, evaluated the utilized geophysical methods, and determined the optimum geophysical methods that can be used for the characterization and monitoring of the subsurface conditions along the entire length of the dam. In this study, we have demonstrated that the integration of effective geophysical surveys and geochemical analysis yielded optimum results in solving a complex dam safety problem. This strategy promotes the best practice for dam safety investigation. [ABSTRACT FROM AUTHOR]

The Xiaolangdi Dam is a key project for the control and development of the Yellow River. It bears the functions of flood control, controlling water and sediment in the lower reaches, ice prevention, industrial and agricultural water supply, power generation, and so on. Its safety is related to people's life and property safety and local economic and social development. It is of great significance to carry out comprehensive and regular deformation monitoring for dams since the deformation is an important evaluation index for dam safety. Interferometric Synthetic Aperture Radar (InSAR) technology has been a rapidly evolving technology in the field of space geodesy in recent years. It offers advantages such as high monitoring precision, extensive coverage, and high monitoring point density, making it a powerful tool for monitoring deformations in hydraulic engineering projects. Based on Sentinel-1 data covering the Xiaolangdi Dam from September 2020 to November 2022, the PS-InSAR technique was used to obtain the surface deformation of the Xiaolangdi Dam, and reservoir water level data on image acquisition dates were obtained for joint analysis. The results show that there is a large deformation in the center of the dam crest of the Xiaolangdi Dam, while both sides of the slope and downstream dam foot are relatively stable. The time series deformation of the dam body is closely related to the reservoir water level change. When the water level increases, the dam body tends to deform downstream; when the water level decreases, the dam body tends to deform upstream. The deformation and water level of the Xiaolangdi Dam exhibit a clear negative correlation. There is no significant cumulative deformation on the dam slopes or at the base of the dam. However, cumulative deformation occurs over time in the central area of the dam's crest. The deformation process at the central area of the dam's crest follows a continuous and non-disruptive pattern, which is consistent with the typical deformation behavior of the Xiaolangdi earth–rock dam structure. Therefore, it is judged that the current deformation of the Xiaolangdi Dam does not impact the safe operation of the dam. InSAR technology enables the rapid acquisition of high-precision, high-density deformation information on the surfaces of reservoir dams. With an increasing number of radar satellites in various frequency bands, such as Sentinel-1 and TerraSAR-X, there is now an ample supply of available data sources for InSAR applications. Consequently, InSAR technology can be extended to routine monitoring applications for reservoir dam deformations, especially for small and medium-sized reservoirs that may not be equipped with ground measurement tools like GNSS. This holds significant importance and potential for enhancing the safety monitoring of such reservoirs. [ABSTRACT FROM AUTHOR]

Erosional incidents have heightened the necessity of studies regarding rock mass erosion in unlined dam spillways. Enhanced comprehension of hydraulic erodibility necessitates an investigation into the geomechanical and hydraulic aspects of erosional phenomena. Controlled blasting is commonly employed to establish unlined spillways in rock masses, and this process results in irregularities along the spillway surface profile. Recent research has identified key geometric parameters of rock masses that impact erosion in unlined spillways, such as joint opening, dip and dip direction, and joint spacing. However, the effect of spillway surface irregularities on hydraulic parameters remains uncertain. Numerous studies have examined the surface roughness of rock at the millimeter scale within the domain of hydraulic engineering. Despite these efforts, a noticeable gap persists in our understanding of how surface irregularities specifically exert influence over hydraulic parameters. Currently, there is a lack of a clear equation or methodology to incorporate irregularities into hydraulic erosive parameters. The main aim of this study is to show how such irregularities affect the hydraulic parameters. This study is dedicated to emphasizing the importance of considering these irregularities. Building upon the findings obtained, the core aim of this research is to facilitate the formulation of an equation in future investigations that effectively accounts for these irregularities when calculating hydraulic erosive parameters. To assess the significance of surface irregularities in unlined spillways, computational fluid dynamics (CFD) with ANSYS-Fluent software was employed to analyze 25 configurations of spillway surface irregularities and their effects on various factors, including pressure (total, dynamic, and static pressures), shear stress, flow velocity, and energy. The findings indicated that irregularities significantly influenced the hydraulic parameters. Specifically, an increased irregularity height led to a decrease in maximum velocity, total pressure, and shear stress. Conversely, total energy loss increased, amplifying the rock mass's vulnerability to erosion due to these irregularities. [ABSTRACT FROM AUTHOR]

This paper presents an innovative digital twin dam and watershed management platform, K-Twin SJ, that utilizes real-time data and simulation models to support decision-making for flood response and water resource management. The platform includes a GIS-based geospatial digital twin of the entire Sumjin dam and river water system in Korea, with high-precision geospatial topography and facility information for dams and rivers (watershed area 4913 km2, river length 173 km, and 91 water infrastructures). The platform synchronizes real-time data such as rainfall, dam and river water levels, flow rate, and closed-circuit television (CCTV), and incorporates three hydraulic and hydrological simulation models for efficient dam operation considering the river conditions. AI technology is also used to predict the river water level and suggest optimal dam discharge scenarios. Additionally, the platform includes a geotechnical safety evaluation module for river levees, advanced drone monitoring for dams and rivers, and an AI CCTV video surveillance function. The digital-twin-based platform supports efficient decision-making for smart flood responses and contributes to reducing flooding damage and optimal operation through better smart water management. [ABSTRACT FROM AUTHOR]

A long-term (1933–2022) record of water level (WL) fluctuations in Lake Kinneret was reviewed. The dependence of the Kinneret WL management on climate change (flood–dryness alternate), dam and National Water Carrier (NWC) constructions constrained by water availability and domestic supply demands were indicated. A short-term range of maximal WL decline of 4–6 m and 4.6–6.5% of the total surface area of lake water shrinkage in Lake Kinneret was documented. Nevertheless, incomparably longer periods and higher amplitudes of WL decline accompanied by a dramatic shrinking of the water surface were documented in Lake Tchad, the Aral Sea and Lake Sivan (SAT). Therefore, the comparative results of WL decline in Lake Kinneret and in other lakes as SAT are not justified. [ABSTRACT FROM AUTHOR]

The impact of the damming of the Sava river for the Brežice hydroelectric power plant on the rise of the groundwater level was studied in the intergranular aquifer of the Krško field and the Vrbina area, Slovenia. The study is based on the application of hydrogen and oxygen isotopes (18O, 2H and 3H). Parameters were determined for precipitation, surface water, and groundwater for periods before and after the filling of the accumulation basin, with the aim of evaluating the groundwater–surface water interaction and to elucidate the impact of the hydroelectric dam on aquifer recharge processes. The results show the proportions of the surface water component in groundwater sampled from four wells at high and low water conditions, separately for the period before and after the filling the accumulation basin. After filling the accumulation basin, the proportion of the Sava river component at high water conditions increased from 60% to 80% in the Brege and Drnovo wells (drinking water resources), from 50% to 80% in the Cerklje well and to almost 100% in the near-river NEK well. Combined with previous studies, the results provide important information about the direction of groundwater flow in the aquifer and improve the conceptual model of the study site. [ABSTRACT FROM AUTHOR]

Dam impoundment can cause many adverse impacts on fish assemblages upstream of dams. Here, we investigated fish diversity in one plateau riverine reservoir (Wanfeng Reservoir) using environmental DNA (eDNA) metabarcoding technology. The following conclusions were drawn: (1) 39 species of fish were monitored belonging to 9 orders and 13 families in the Wanfeng Reservoir, most of which were Cypriniformes and included a variety of common farmed fish belonging to Culter, Oreochromis, Acipenser, and Clarias; (2) the fish assemblage structures in the Up (upstream section), Mid (midstream section), and RA (reservoir area section) of this reservoir was significantly different (p-value < 0.01); (3) among the 7 environmental variables that were measured (Tem, TDS, Sal, pH, DO, NH4+, and Tra), DO (p-value < 0.01) and pH (p-value < 0.05) were the main environmental stressors causing differences in fish assemblages in different sites of the Wanfeng Reservoir. This study concluded that dam construction in the karst region provided habitats for the establishment and dispersal of exotic fish. [ABSTRACT FROM AUTHOR]

This paper examines whether lime can be used for the drainage of cohesive soils built into hydraulic engineering embankments. It is a common practice, as early as the planning stage, to seek to reduce costs and accelerate work while maintaining the quality of work. Although lime stabilisation is not currently a widely used solution in the hydraulic engineering sector, it can play an important role in the future. Lime stabilisation can be considered an optimal solution as it shortens the embankment construction by eliminating the need to replace the soil when it is over-wet. This paper investigates whether it is possible to apply lime treatment in the forming of hydraulic engineering embankments as well as analyses the efficiency of mechanical soil drainage and compares it against chemical drainage (lime stabilisation) based on the example of the construction of the Szalejów Górny dry flood control reservoir located in south-western Poland. It presents the results of geotechnical investigations carried out during the construction phase and compares them with cases reported in the literature. The observation of the construction process reveals a high efficiency and effectiveness of quicklime (CaO) as a stabiliser in the soil used for reservoir dams. Adoption of this technology made it possible to achieve significantly higher embankment formation rates (max. approx. 14,000 m3/week) than when mechanical drainage was used (max. approx. 11,000 m3/week). It was also noted that the lime stabilisation process was significantly independent of unfavourable weather conditions, resulting in frequent high weekly efficiencies. Geotechnical tests on samples of the lime-stabilised soil built into the dam body confirmed the possibility of obtaining favourable strength parameters, particularly with regard to the angle of internal friction, cohesion and degree of plasticity. Therefore, it can be expected that lime will be used more widely in the formation of hydraulic engineering embankments and that soil stabilisation technology will be applied more frequently. [ABSTRACT FROM AUTHOR]

Dam construction for the provision of hydropower and a stable water supply poses a major threat to freshwater biodiversity. Water fluctuation due to dam management has adverse effects on local people and biodiversity in downstream areas, including sandbar-nesting birds. The aim of this research was to determine the effect of water levels controlled by upstream dams on the breeding success of two sandbar-nesting birds, the little ringed plover, Charadrius dubius, and little pratincole, Glareola lacteal, along the Mekong River in Bueng Kan Province, Thailand. During January–May 2018, we found 160 active nests of only two species, the little ringed plover (n = 26 nests, 288 exposure days) and the little pratincole (n = 134 nests, 890 exposure days). Their nest success rates were 19.49 ± 7.52% and 5.54 ± 1.61%, respectively. Predation was a major cause of nest failure for both species (n = 82), followed by flooding (n = 44). We found a significantly increased probability of nest flooding when the water level was higher than when the nest was initiated for those located closer to the water, particularly during March and April, when water levels fluctuated. Our results indicate that dams threaten sandbar-nesting species. [ABSTRACT FROM AUTHOR]

Changes in the stream flow contribute to transformation of the river channel due to erosion and accumulation. Channel bars move as a result of water flow. This article presents the results of studies carried out on two channel bars formed in the River Vistula that were transformed during emergency discharges of water from the Włocławek reservoir. In order to present changes in structure and texture, pits were dug in the channel bars and samples were taken for grain-size analysis. The rate of migration of channel bars caused by emergency discharges was determined. Sedimentary structures were recorded as groups of strata indicating a variability in flow conditions (2D and 3D dunes, parasitic ripple marks, reactivation surfaces). It was observed that changes in the level of water and flow are reflected in sedimentary structures. The emergent channel bars are affected by aeolian processes that wear the flow marks off. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAVs) are now filling in the gaps between spaceborne and ground-based observations and enhancing the spatial resolution and temporal coverage of data acquisition. In the realm of hydrological observations, UAVs play a key role in quantitatively characterizing the surface flow, allowing for remotely accessing the water body of interest. In this paper, we propose a technology that uses a sensing platform encompassing a drone and a camera to determine the water level. The images acquired by means of the sensing platform are then analyzed using the Canny method to detect the edges of water level and of Ground Control Points (GCPs) used as reference points. The water level is then retrieved from images and compared to a benchmark value obtained by a traditional device. The method is tested at four locations in an artificial lake in central Italy. Results are encouraging, as the overall mean error between estimated and true water level values is around 0.05 m. This technology is well suited to improve hydraulic modeling and thus provides reliable support to flood mitigation strategies. [ABSTRACT FROM AUTHOR]

Most European riverine ecosystems suffer from the negative influence of impoundments on flow regime. Downstream effects of dams lead to a number of environmental and socioeconomic risks and, therefore, should be thoroughly examined in specific contexts. Our study aims to quantify the downstream effects of the Siemianówka Reservoir (Upper Narew, Poland), using statistical analysis of key elements of the river's flow regime, such as the flow duration and recurrence of floods and droughts. In a comparative study on control catchments not influenced by impoundments (the Supra'sl and Narewka Rivers), we revealed the following downstream effects of the analyzed dam: significant shortening of spring floods, reduction of the duration and depth of summer droughts, decrease of the maximum discharge, and homogenization of the discharge hydrographs. Although we determined a significant decrease in the duration of summer floods in the "before" and "after" dam function periods, we showed that this issue is regional, climate-related, and replicated in control catchments, rather than an evident downstream effect of the dam. We conclude that significant hydrological downstream effects of the Siemianówka dam-reservoir system could have been the main driver inducing the deterioration of the anastomosing stretch of the Narew River downstream of the dam. [ABSTRACT FROM AUTHOR]

Groundwater depletion poses a significant threat in arid and semi-arid areas where rivers are usually ephemeral and groundwater is the major source of water. The present study investigated whether an effective water resources management strategy, capable of minimizing evaporative water losses and groundwater depletion while providing water for expanded agricultural activities, can be achieved through aquifer storage and recovery (ASR) implemented in conjunction with water storage in an ephemeral river. A regional development modeling framework, including both ASR and a dam design developed through system dynamics modeling, was validated using a case study for the Sirik region of Iran. The system dynamics model of groundwater flow and the comprehensive system dynamics model developed in this study showed that ASR was a beneficial strategy for the region's farmers and the groundwater system, since the rate of groundwater depletion declined significantly (from 14.5 meters per 40 years to three meters over the same period). Furthermore, evaporation from the reservoir decreased by 50 million cubic meters over the simulation period. It was concluded that the proposed system dynamics model is an effective tool in helping to conserve water resources and reduce depletion in arid regions and semi-arid areas. [ABSTRACT FROM AUTHOR]

Groundwater depletion poses a significant threat in arid and semi-arid areas where rivers are usually ephemeral and groundwater is the major source of water. The present study investigated whether an effective water resources management strategy, capable of minimizing evaporative water losses and groundwater depletion while providing water for expanded agricultural activities, can be achieved through aquifer storage and recovery (ASR) implemented in conjunction with water storage in an ephemeral river. A regional development modeling framework, including both ASR and a dam design developed through system dynamics modeling, was validated using a case study for the Sirik region of Iran. The system dynamics model of groundwater flow and the comprehensive system dynamics model developed in this study showed that ASR was a beneficial strategy for the region's farmers and the groundwater system, since the rate of groundwater depletion declined significantly (from 14.5 meters per 40 years to three meters over the same period). Furthermore, evaporation from the reservoir decreased by 50 million cubic meters over the simulation period. It was concluded that the proposed system dynamics model is an effective tool in helping to conserve water resources and reduce depletion in arid regions and semi-arid areas. [ABSTRACT FROM AUTHOR]

An adaptive neuro-fuzzy inference system (ANFIS) was developed using the subtractive clustering technique to study the air demand in low-level outlet works. The ANFIS model was employed to calculate vent air discharge in different gate openings for an embankment dam. A hybrid learning algorithm obtained from combining back-propagation and least square estimate was adopted to identify linear and non-linear parameters in the ANFIS model. Empirical relationships based on the experimental information obtained from physical models were applied to 108 experimental data points to obtain more reliable evaluations. The feed-forward Levenberg-Marquardt neural network (LMNN) and multiple linear regression (MLR) models were also built using the same data to compare model performances with each other. The results indicated that the fuzzy rule-based model performed better than the LMNN and MLR models, in terms of the simulation performance criteria established, as the root mean square error, the Nash-Sutcliffe efficiency, the correlation coefficient and the Bias. [ABSTRACT FROM AUTHOR]

Riverine dams alter both the physical environment and water chemistry, thus affecting species assemblages within these environments. In the United States, dam construction is on the decline and there is a growing trend for dam removal. The Choctawhatchee, Pea, and Yellow Rivers Watershed Management Authority had initiated the permitting process for placing a reservoir dam on the Little Choctawhatchee River (LCR), a tributary to the Choctawhatchee River. The purpose of the proposed reservoir was water supply, and while the permit application has been suspended, history shows that this or related projects are likely to arise in the future. This study collected data on nutrient quality seasonally (four times) from 12 sites in the LCR watershed from October 2007 to June 2008 in order to determine pre-dam conditions and to compare these data to historical and regional information. Historical and current nutrient concentrations were elevated throughout the watershed, in most cases above suggested criteria, and indicated that water quality of the river was and continues to be nutrient rich. A future reservoir at recent levels of water quality will likely be highly eutrophic, and anthropogenic influences will further stress this ecosystem and its water quality as the urban region expands. [ABSTRACT FROM AUTHOR]

The interannual variability of streamflow affects the composition and species richness of vegetation in low-flow channels and alluvial plains. Although climate conditions in 2003 and 2004 were nearly identical, large differences in streamflow were observed downstream from the Matawin dam. These differences resulted in numerous days without flow (no water release) during the growing period (May to August) in 2003, leading to man-made hydrological drought. While this drought had no effect on abiotic variables (grain-size distribution and nutrient concentrations in sediments), a significant decrease in the number of terrestrial species was observed in 2004 (year without drought) relative to 2003 (drought year) on three sand bars studied. This decrease is interpreted to result from prolonged submergence of the sites in 2004. Principal component analysis highlighted the effect of individual sites (first principal component) and of the interannual variability of streamflow (second component) on the number of species. The study suggests that, from a flow management standpoint, it is advisable to release enough water downstream from the dam during the growing season to prevent low-flow channel colonization by invasive terrestrial species. [ABSTRACT FROM AUTHOR]

In recent years, rock scouring or erosion downstream of dams has become an increasing dam safety concern. Several theoretical, semi-theoretical, semi-analytical and numerical methods can be used to assess the rock erosion in hydraulic structures. Semi-theoretical approaches determine the correlation between the erosive intensity of fluid flow and the resistive capacity of rock. Such approaches establish the scour thresholds as a function of erosive intensity of water and several rock mass indices by using in situ data and a curve-fitting approach. In some studies, the excavatability index, initially developed for rock mass stability analysis, was used to analyse the rock mass resistance in hydraulic erodibility analysis. The effectivity and weight of the geomechanical parameters used are yet to be determined on the basis of the erodibility phenomenon. The semi-analytical methods are developed on the basis of the mechanical and hydraulic interaction of rock mass and water. Four methods developed by Bollaert et al. are important in determining the erodibility in the plunge pool, but they are not applicable in the case of spillways. They used the comprehensive fracture mechanics for closed-end joints, quasi-steady impulsion, and dynamic impulsion (DI) for blocky rock erosion. The application of these methods to each site is necessary to identify constants that are difficult to determine. Few numerical methods are available to assess the rock mass erosion in hydraulic structures. In the case of numerical methods, the erosive agent is indistinct, and the hydraulic hazard parameter on the spillway surface is almost challenging to apply. This study comprehensively reviews the mechanism of erosion and the methods for assessing the risk of potential rock mass erosion downstream of dams and hydraulic structures. The advantages and disadvantages of all methods are discussed and the potential future research directions in this domain are proposed. [ABSTRACT FROM AUTHOR]

Spillways with Highly Converging Chutes (HCCs) are a non-conventional alternative that can be applied to achieve a higher outflow capacity when the weir length exceeds the width of the valley at the toe of gravity or arch dams. This kind of spillway has been used in the past, but no general studies have yet been published. This article summarizes experimental research work aiming to increase the knowledge of the effect of some design parameters of HCCs on the energy dissipation in the stilling basin at the toe of the dam. As a comparison reference, we use the Type I stilling basins, widely known by the technical dam engineering community. The obtained results show that spillways with HCCs are a promising alternative to traditional designs, combining the ability to increase the weir length with a high capacity to dissipate energy through the impingement effect of the frontal and the side jets inside the stilling basin. [ABSTRACT FROM AUTHOR]

The estimation of the design peak discharge is crucial for the hydrological design of hydraulic structures. A commonly used approach is to estimate the design storm through the intensity–duration–area–frequency (IDAF) curves and then use it to generate the design discharge through a hydrological model. In ungauged areas, IDAF curves and design discharges are derived throughout regionalization studies, if any exist for the area of interest, or from using the hydrological information of the closest and most similar gauged place. However, many regions around the globe remain ungauged or are very poorly gauged. In this regard, a unique opportunity is provided by satellite precipitation products developed and improved in the last decades. In this paper, we show weaknesses and potentials of satellite data and, for the first time, we evaluate their applicability for design purposes. We employ CMORPH—Climate Prediction Center MORPHing technique satellite precipitation estimates to build IDAF curves and derive the design peak discharges for the Pietrarossa dam catchment in southern Italy. Results are compared with the corresponding one provided by a regionalization study, i.e., VAPI—VAlutazione delle Piene in Italia project, usually used in Italy in ungauged areas. Results show that CMORPH performed well for the estimation of low duration and small return periods storm events, while for high return period storms, further research is still needed. [ABSTRACT FROM AUTHOR]

Flow regulation by large dams has transformed the freshwater and floodplain ecosystems of the Middle Amur River basin in Northeast Asia, and negatively impacted the biodiversity and fisheries. This study aimed to develop environmental flow recommendations for the Zeya and Bureya rivers based on past flow rate records. The recommended floodplain inundation by environmental flow releases from the Zeya reservoir are currently impracticable due to technical reasons. Therefore, the importance of preserving the free-flowing tributaries of the Zeya River increases. Future technical improvements for implementing environmental flow releases at the Zeya dam would improve dam management regulation during large floods. The recommendations developed for environmental flow releases from reservoirs on the Bureya River should help to preserve the important Ramsar wetlands which provide habitats for endangered bird species while avoiding flooding of settlements. The results emphasize the importance of considering environmental flow during the early stages of dam planning and the need to enhance the role of environmental flow in water management planning. [ABSTRACT FROM AUTHOR]

The evaluation and quantification of solids transport in Morocco often uses the Universal Soil Loss Model (USLE) and the revised version RUSLE, which presents a calibration difficulty. In this study, we apply the MUSLE model to predict solid transport, for the first time on a large river basin in the Kingdom, calibrated by two years of solid transport measurements on four main gauging stations at the entrance of the Sidi Mohamed Ben Abdellah dam. The application of the MUSLE on the basin demonstrated relatively small differences between the measured values and those expected for the calibrated version, these differences are, for the non-calibrated version, +5% and +102% for the years 2016/2017 and 2017/2018 respectively, and between −33% and +34% for the calibrated version. Besides, the measured and modeled volumes that do not exceed 1.78 × 106 m3/year remain well below the dam's siltation rate of 9.49 × 106 m3/year, which means that only 18% of the dam's sediment comes from upstream. This seems very low because it is calculated from only two years. The main hypothesis that we can formulate is that the sediments of the dam most probably comes from the erosion of its banks. [ABSTRACT FROM AUTHOR]

This paper analyzes the importance of the cost of dam water use in hydroelectric generators according to the International Financial Reporting Standard (IFRS) and Management Accounting. Not valuing the use of water from dams would imply undervaluing energy generation service, leading to a lack of reasonability in the Financial Statements of electricity generators. For this reason, it is vital to recognize that dam water has a cost that directly impacts the Statement of Financial Position as an asset and later, in energy generation and commercialization, its cost will impact the statement of profit or loss, according to the IFRS as good accounting and financial practices around the world. Said cost will also be an important indicator for rationalizing consumption, defining public policy, or determining energy tariffs. An empirical study is conducted for Colombia and Norway, two of the main countries in the world whose primary source of energy generation is water. The results evidence the need for hydroelectric generators to present the cost of their hydric reserve as intangibles inventories because of its potential capacity to generate electric power. Additionally, there is a positive and significant relationship between the cost of water and the price of energy, and a negative relationship between the price of energy and dam levels. [ABSTRACT FROM AUTHOR]

Hydropower development causes a multitude of negative effects on freshwater ecosystems, and to prevent and minimize possible damage, environmental impact assessments must be conducted and optimal management scenarios designed. This paper examines the impacts of both existing and proposed hydropower development on the transboundary Amur River basin shared by Russia, China, and Mongolia, including the effectiveness of different tools and measures to minimize damage. It demonstrates that the application of various assessment and conservation tools at the proper time and in the proper sequence is the key factor in mitigating and minimizing the environmental impacts of dams. The tools considered include basin-wide assessments of hydropower impacts, the creation of protected areas on rivers threatened by dam construction, and environmental flows. The results of this work show how the initial avoidance and mitigation of hydropower impacts at early planning stages are more productive than the application of any measures during and after dam construction, that the assessment of hydropower impacts must be performed at a basin level rather than be limited to a project implementation site, and that the full spectrum of possible development scenarios should be considered. In addition, this project demonstrates that stakeholder analysis and robust public engagement are as crucial for the success of environmental assessments as scientific research is for the protection of river basins. [ABSTRACT FROM AUTHOR]

In this paper, we present a method to assess the influence of the initial reservoir level in hydrological dam safety and risk analysis. Traditionally, in professional practice, the procedures applied are basically deterministic. Several physical processes are defined deterministically, according to the criteria of the designer (usually in the conservative side), although there is a high degree of uncertainty regarding these processes. A relevant variable is the reservoir level considered at the beginning of flood events. Hydrological dam safety assessment methods traditionally assume that the reservoir is initially full when it receives the design flood, thus, staying in the conservative side when designing a new dam. However, the distribution of reservoir levels at the beginning of flood episodes takes more importance for evaluating the real risk for the dams in operation. We analyzed three different scenarios—initial reservoir level equal to maximum normal level, equal to a maximum conservation level, and following the probability distribution from the historical records. To do so, we presented a method applied to a gated-spillway dam located in the Tagus river basin. A set of 100,000 inflow hydrographs was generated through a Monte Carlo procedure, by reproducing the statistics of the main observed hydrograph characteristics—peak flow, volume, and duration. The set of 100,000 hydrographs was routed through the reservoir applying the Volumetric Evaluation Method as a flood control strategy. In order to compare the three scenarios, we applied an economic global risk index. The index combines the hydrological risk for the dam, linked to the maximum water level reached in the reservoir, during the flood routing, and the flood risk in the downstream river reach, linked to the discharge releases from the dam. The results showed the importance of accounting for the fluctuation of initial reservoir levels, for assessing the risk related to hydrological dam safety. Furthermore, a procedure to quantify the uncertainty associated with the effects of initial reservoir level on hydrological dam safety, has been proposed. [ABSTRACT FROM AUTHOR]

This paper analyzes contestation over aspects of the Site C Project on the Peace River in northeastern British Columbia, Canada. The $10.7 billion project, which is now under construction, has been vigorously debated for over 30 years. Initially proposed in the 1980s, project approval was not granted following review by the BC Utilities Commission, as the need for the project was not established. In 2010, the provincial government enacted legislation to exempt the project from future review by the BC Utilities Commission; an environmental assessment was initiated in 2012 and a constrained review by the Commission was undertaken in 2017, after construction had commenced. The paper explores key examples of contested knowledge regimes within the review process, focusing on debates over cumulative effects and greenhouse gas emissions. The analysis provides technical examples of the ways in which differing societal values are deployed and co-produced within regulatory processes. [ABSTRACT FROM AUTHOR]

An increasing number of scientific studies are tackling the management of discharges downstream of dams for environmental objectives. Such management is generally complex, and experiments are required for proper implementation. This article present the main lessons from a silt sand removal experiment on a bypassed reach of a dam on the Selves River (164 km²), France. Three four-hour operational tests at maximum discharge (10, 15, and 20 m3/s) were carried out in September 2016 to determine the discharge required for transporting as much silt and sand as possible without remobilizing coarser sediments. In September 2017, an additional flow release was performed over 34 h at 15 m3/s. Suspended sediment concentration and water level were recorded throughout the releases. Monitoring at the reach scale was supplemented by morphological measurements. The results demonstrate that a discharge of approximately 10 m3/s enables significant transport of suspended sediments (SS), whereas a discharge of 15 m3/s enables significant sand transport. The results provide operational information on silt and sand transport applicable to other small rivers. This study represents an important contribution to the relatively sparse existing body of literature regarding the effects of water releases and sediment state. Our study also demonstrates that it is possible to successfully undertake water releases in small rivers with an adaptive management approach. [ABSTRACT FROM AUTHOR]

The Three Gorges Project (TGP) is the largest hydroelectric project in the world. It is crucial to understand the relationship between runoff regime changes and TGP's full operation after 2009 in the Yangtze River Basin (YRB). This paper defines core, extended and buffer areas of YRB, analyzes the effects of TGP on runoff anomaly (RA), runoff variation (RV) and change of coefficient of variation (CCV) between two periods (2003–2008 and 2009–2016), takes percentage of runoff anomaly (PRA) as the evaluation standard, assures alleviation effect on severe dry and wet years of the research area, and finally summarizes related benefits of flood control from TGP. Our results indicate the inter-annual fluctuation of runoff in the core and extended areas expanded, but reduced in the buffer areas, and the frequencies of severe dry and wet years alleviated in the buffer, core and extended areas. Generally, the extended and core areas become less wet, and the buffer areas become less dry. The RV and CCV are both strengthened in the extended and core areas, but are weakened in the buffer areas, and RV is well positively correlated (R2 = 0.80) to CCV. Furthermore, the main benefits of TGP on flood control are remarkable in the reduction of disaster affected population, the decrease of agricultural disaster-damaged area, and the decline of direct economic loss. However, due to torrentially seasonal and non-seasonal precipitation, the sharp rebounds of three standards for Hubei and Anhui occurred in 2010 and 2016, and the percentage of agricultural damage area of five regions in the core and extended areas did not decline synchronously and performed irregularly. Our results suggest that the five key regions along the main branches of the Yangtze River should establish a flood control system and promote the connectivity of infrastructures at different levels to meet the significant functions of TGP. It is a great challenge for TGP operation to balance the benefits and conflicts among flood control, power generation and water resources supply in the future. [ABSTRACT FROM AUTHOR]

This article investigates how the "constructivist turn" in public policy and international political economy informs the interaction of global ideas and local practice in water governance. We use the implementation of ideas associated with Integrated Water Resources Management (IWRM) in the Lower Mekong river basin. This article provides some explanation of the attitudes in the villages in Cambodia due to the Sesan 2 Dam, which would see the relocation of thousands of people, damage fisheries, and inflict high coping costs on villagers. Based on 24 in-depth interviews with villagers, commune heads and local community leaders, we find diverse narratives which transcend the "pro or anti" dam narrative. We find four narrative types—myths, stories, noise and informed opinion, which relate to each other in degrees of social meaning and ideational force. Of these, the first two are more likely to be useful in terms of mobilization and policy-making. This typology provides a framework for analysis of social change in the studied villages and other contexts of policy translation. We should state that these four types are not separate from each other but are linked along two axis which together conscribe the four types of narratives outlined. [ABSTRACT FROM AUTHOR]

Reservoir design entails the determination of the required storage capacity over multiple years of low flow conditions to ensure the coverage of multiple-purpose water demands. Dam operation depends on many factors that may result in the decrease of required safe yields, leading to inadequate outflow supplies in the design period. This study addresses two issues: (a) the computation of reservoir active storage capacity performed with the aid of the new concept of a zero-height dam, a procedure easy to interpret physically and implement computationally; and (b) the generation of appropriate inflow data, provided that a substantial record of monthly inflows is available. The treatment of the inflow data for the generation of inflow sequences for any desired regulation period is performed by two original methods (First and Second), which are entirely different from other available methods and allow for the selection of a reservoir capacity with the desired level of exceedance probability. The two methods proposed give practically the same results. However, the Second Method, which generates inflow data consisting of hydrologic years with inflow values for each month randomly selected from the observed values for that month, is superior in terms of the ease with which inflow sequences are generated. Also, due to the large size of the random sample that can be generated, the exceedance probability curves are very smooth and allow for the easy selection of reservoir storage capacity with any level of desired exceedance probability. The proposed methodology may be useful for consultants and reservoir managers. [ABSTRACT FROM AUTHOR]

Debris flow injections from tributaries into a main mountain stream generate deposits of sediments which, in turn, result in obstruction and eventual damming of the river section. This contribution presents the results of a series of flume experiments on the dynamics of these deposits, with reference to three different types of blockage: no blockage, partial blockage, and full blockage. Results show that the shape of the deposit is mainly controlled by the ratio between the debris flow discharge and the main river discharge. The experimental dataset is used to develop a deposit resilience stability index based on the shape of the deposit contour retrieved from photos taken from above. The proposed index is based on the invariant elliptic Fourier coefficients and the dimensionless transverse obstruction parameter. The elliptic Fourier coefficients give information on the symmetry of the deposit contour. High symmetry indicates more stable and resilient deposits. The proposed index is calibrated on the basis of the flume experiments and tested with field data. The results are quite promising and suggest that the index can be appropriate for a fast hazard assessment of multiple debris flow deposits at a regional scale. [ABSTRACT FROM AUTHOR]