River Damming Research Articles

Greenhouse gas concentrations and diffusive fluxes in the middle reach of the Lancang River before and after damming

With increasing concerns of greenhouse gas (GHG) emissions from reservoirs, the debate surrounding whether hydropower qualifies as green energy has become increasingly contentious. However, quantifying the impact of dam construction on river GHG emissions still poses challenging due to the absence of direct observational data on river GHG emissions pre- and post-damming. In the present study, the differences in GHG diffusive fluxes from pre- and post-dammed river channels in the middle reaches of the Lancang River were quantified through three field campaigns in 2016, 2018, and 2023. The results indicate that reservoir construction increases the diffusive fluxes of GHG from the natural river, the total GHG emissions (expressed as carbon dioxide equivalent: CO2eq) from post-dammed river ranged from 234.42 to 527.55 mg CO2eq m−2 d−1 and were 1.4–5.2 times higher than that from pre-dammed river. However, the GHG diffusive fluxes from the reservoirs in the Lancang River remain below the average of global reservoirs. Moreover, river damming enhances the methane (CH4) emissions, the average value of CH4/CO2 ratio (in mg m−2 d−1) was 0.003 post-dam and was 13 times higher than that of pre-dam. Our results revealed that alterations in sediment distribution following reservoir construction emerge as a pivotal factor contributing to the variations in spatial distributions of GHG diffusive fluxes in the studied river channel. Overall, the findings of the study provide a primary and direct evidence of river damming impact on GHG emissions and underscore the necessity of long-term continuous in-situ measurements of GHG fluxes in the rivers undergoing hydropower development.

Hydrological and morphological responses in the São Francisco River Basin (Northeast Brazil) resulting from river damming and climate changes in a tropical region

Hydrological and morphological responses in the São Francisco River Basin (Northeast Brazil) resulting from river damming and climate changes in a tropical region

CATALOG OF LANDSLIDES OF THE CITY OF ZENICE WITH SPECIFIC CAUSES

As part of its activities, the Federal Institute of Geology carries out mapping of active landslides in the territory of the Federation of Bosnia and Herzegovina, and my task is to map instability in the area of the City of Zenica. A very large number of landslides were registered during the catastrophic rainfall that occurred in 2014. Following these phenomena and certain records, detailed mapping of unstable slopes and records of unstable surfaces was started. The cadastre is defined in such a way that it displays all input data with location polygons in GIS. Not in the field, quite recognizable causes were observed, which are always a combination of bad geological and hydrogeological conditions with a significant anthropogenic factor. The slope of the terrain is also very unfavourable, and gravity also played a significant role in the instability of these slopes. Almost all registered landslides have unregulated water (surface, underground, waste). The frequent occurrence of earthquakes on this section also significantly threatened the stability of slopes and buildings, and on the spot, the consequences of cracking and shearing of buildings were evident as a result of the earthquake. A special review will be given to the activation of mudflows during extensive rainfall in this area, which is not rare. A significant share in the formation of mudflows belongs to heavy precipitation, which over time formed the so-called "watersheds" where water was transported from higher to lower parts of the slope. However, during the climate changes, there was a significant increase in the amount and frequency of precipitation, which carried the surface cover and rock blocks that were moved down the steep slopes. Road approaches to the villages, as well as a significant number of buildings, made artificial dams and cut cuts that were a natural way of draining water. So you have a significant number of buildings built exactly on these "watersheds" that represent the dam. In the newly created situation, by changing the natural paths of movement of surface and underground water, it would be necessary to regulate the water below and around the road strip, as well as the drainage of water around buildings. Only after the water has been drained, certain geotechnical procedures can be carried out to stabilize the slope and to permanently rehabilitate it, so that the inhabitants of these villages do not constantly fear during rainfall.

Stochastic hazard assessment framework of landslide blocking river by depth-integrated continuum method and random field theory

AbstractLandslide-induced barrier dams pose a threat to the safety of humans, livestock and nearby infrastructures. The efficient assessment of landslide blocking river is crucial for disaster prevention and mitigation solutions. This study proposes a novel stochastic assessment framework to evaluate the landslide blocking river through the prediction of their deposition depths and considering the heterogeneity of shear strength parameters on the potential sliding surface. The depth-integrated continuum method (DICM) is used to simulate the landslide runout process. Using an enhanced Karhunen-Loève expansion (KLE) method, the spatial variations in soil's shear strength parameters are modeled by random fields to incorporate the effects of soil's spatial heterogeneity on the landslide deposition pattern. Subsequently, the multi-response surrogate model is constructed to relate the random field variables to the deposition depths based on extreme gradient boosting (XGBoost). To improve the performance of the surrogate model, principal component analysis (PCA) and sliced inverse regression (SIR) methods are employed for the dimension reduction of output and input variables, respectively. Furthermore, the algorithm for river blockage identification is developed to search for the deposition ridges. To demonstrate the capability of the stochastic assessment framework, an example of the first Baige landslide in Tibet, China is simulated, and the affected region and deposition depths of the landslide are predicted to calculate the probability of river damming. The presented methodology provides a practical means for improving the landslide blocking river prediction and new insights for early warning and risk mitigation.

River Damming Impacts on Carbon Emissions Should Be Revisited in the Context of the Aquatic Continuum Concept.

River Damming Impacts on Carbon Emissions Should Be Revisited in the Context of the Aquatic Continuum Concept.

Catastrophic outburst floods along the middle Yarlung Tsangpo River: Responses to coupled fault and glacial activity on the Southern Tibetan Plateau

The immense outburst floods that have occurred on the Tibetan Plateau during the Late Quaternary are closely linked to tectonic and climatic factors. These floods likely induced very rapid, short-term geomorphic impacts on the evolution of mountain drainage systems and patterns of sedimentary movement. In this study, four glacially-dammed lake outburst flood events that occurred along the middle reaches of the Yarlung Tsangpo River since the Middle Pleistocene were reconstructed by combining comprehensive geomorphic, stratigraphic and geochronologic investigations. The most recent outburst flood sequence occurred at ∼10.5 ka, with a peak discharge of ∼5 × 105 m3/s. The tilted uplift of the Cona Normal Fault has resulted in localized topographic lift and the formation of river knickpoints, contributing to the development and stabilization of glacial dams. River damming and outburst events have also been influenced by glacial-interglacial climate fluctuations since the Middle Pleistocene. The focused erosion and extensive mobilization of sediment by these low-frequency, high-energy floods have resulted in a repeated pattern of material transport and deposition from the Tibetan Plateau interior to its exterior. Coupled with glacial activity, the primary factor impacting the sustained stability of knickpoints on the Yarlung Tsangpo River along the Tibetan plateau's southern margin has been differential rock uplift, which results in a distinct geomorphic pattern characterized by knickpoints, glacial dams and alternating wide valleys and deep gorges.

Nubian aquifer linkage to the High Aswan Dam Reservoir: Initial assessments of processes and challenges

Egypt, relying heavily on the Nile as its primary water resource, is facing a rising water budget deficit due to increasing consumption, hydroclimatic changes, and upstream river damming. To address the above, innovative management of High Aswan Dam Reservoir (HADR), the third largest artificial reservoir on Earth, and its exchange with the surrounding groundwater system is suggested to develop new agricultural areas. However, the interconnectivity mechanism between the HADR and the fossil Nubian aquifer, the largest transboundary aquifer in Africa, remains speculative due to the lack of in-situ investigations. To address this deficiency, we perform a geophysical survey using aeromagnetic, time-domain electromagnetic, and vertical electrical resistivity sounding in a 330 km2 pilot area to the northwest of the HADR that is hypothesized to have a dense fracture system that could act as a conduit between these two large water bodies. Our survey results show the presence of normal faults cross the reservoir to the tangential basement and the sedimentary cover that are water-saturated and act as recharges to the Nubian fossil aquifer. These in-situ investigations confirm previous orbital gravity observations by GRACE-FO hypothesizing the interconnectivity between the reservoir and the Nubian aquifer, which was subject to debate. We suggest that such connecting areas between these two water bodies can be optimal sites for future agricultural development using improved management of surface water-groundwater exchanges for irrigation. Finally, our findings highlight upcoming challenges for this linkage if the level of HADR reaches below ∼160 m above mean sea level (amsl) due to upstream dam operation during the Nile’s extended drought periods. Under these conditions, the Nubian aquifer could discharge back into the HADR at the investigated site, changing the water budget of the aquifer and compromising the planned agriculture developments in the adjacent areas, which account for ∼ 10 % of the total arable land in Egypt.

Ecohydraulics-based environmental flow assessment in two arid North African rivers

North Africa is among the most water-stressed regions in the world; still, the habitat requirements of its freshwater biota are largely unknown. In this study, (i) we developed habitat suitability curves (HSCs) for freshwater macroinvertebrates in two poorly studied, regulated North African rivers (Ziz and Oum Er-Rbia), and (ii) assessed environmental flows downstream of each river dam by incorporating the HSCs in two-dimensional ecohydraulic models. We demonstrate a low-cost sampling methodology combined with freely distributed ecohydraulic modeling software. The results showed that macroinvertebrates in the arid-desert Ziz River could tolerate a wide range of habitats in terms of flow velocity and water depth compared to the arid-steppe Oum Er-Rbia River, probably due to their adaptation to extreme (arid-desert) environmental conditions. Optimal environmental flows downstream of the Al Hassan Addakhil (Ziz River) and the Al Massira (Oum Er-Rbia River) dams were 1 m3/s and 2 m3/s, respectively. However, environmental flows at 0.5 m3/s and 1 m3/s, respectively, could still maintain sustainable freshwater biota downstream of the dams. The results further highlight the critical status of the Ziz River, which was completely dry, and the alarming status of the Oum Er-Rbia River due to the significant reduction in the water levels of the Al Massira Dam. In a continuously changing climate, we suggest that the proposed environmental flows should be immediately delivered to prevent droughts and ensure healthy freshwater communities downstream of the dams, within a basin-wide freshwater management framework. In this water scarce region, more research is necessary to increase ecological awareness about these understudied freshwater systems and achieve a balance between human needs and ecosystem requirements.

Eucarid and Peracarid Fauna of the Valencia Seamount, a Deep-Isolated Seamount of the Western Mediterranean: Colonisation Capacity and Historical Changes

Seamounts can have a strong influence on the distribution and diversity of species, creating an oasis effect that may favour diversification. In order to assess how and to what extent supra- and epibenthic crustaceans can colonise these environments, the eucarid and peracarid fauna collected from the summit of the Valencia Seamount (VS), a small deep seamount (summit depth: 1056 m), rising from a depth of ca. 1850 m, in the oligotrophic Balearic Basin, was analysed. Based on a first sampling (beam trawls, plankton nets and stomach contents), and a faunal reconstruction from a sediment core (MC2, at 1151 m), the supra(epi)benthic crustaceans at the VS summit (to 1300 m) were composed of nine Eucarida and 25 Peracarida. Polycheles typhlops, Munida tenuimana, and Aristeus antennatus were the dominant species among eucarids. Among Peracarida the most abundant species were the Mysida Boreomysis arctica, the Amphipoda Rhachtropis caeca, and the Isopoda Munnopsurus atlanticus. Among Decapoda, a species with a wide amplitude in their depth distribution and small eggs (i.e., with planktotrophic larvae), showed a higher colonisation capacity. In the absence of larvae, the colonisation of peracarids depends on the amplitude of their depth distribution and only those species that reach the highest depths in the entire Balearic Basin, at least 1600–1800 m, were able to colonise the summit of VS. The natatory capacity of the species also has some influence and whole groups with low natatory capacity, such as the Desmosomatidae, were completely absent on the VS summit; however, they are distributed throughout the Balearic Basin to depths (up to about 1500 m) exceeding the depth of the seamount summit. Therefore, colonisation by peracarids must not have occurred by swimming through the entire water column, but by swimming along or just above the bottom. Remains of some suprabenthic species (mainly the isopod M. atlanticus) in MC2 and another core collected in NW Mallorca (MC3, 1114 m), i.e., out of the VS, showed how isopod diversity and size distribution changed historically. Also, after the 1960s, a decrease in primary production due to a decrease in rainfall and river runoff associated with river damming could have reduced the abundance of M. atlanticus. These types of historical studies can be useful in interpreting long-term changes in deep-sea communities and optimising the management of these vulnerable areas.

Recurrence interval of riverbed sand mining hotspots in the Mekong delta: Potential indications of unsustainable replenishment rates

Rampant and illegal river sand mining in the Vietnamese Mekong Delta (VMD) has led to substantial sediment losses and bank erosion. However, regulation of this issue remains a significant challenge due to insufficient monitoring and enforcement efforts, partly attributed to limited data and technology. To support an improved monitoring system in the VMD, this study investigates the spatiotemporal changes in sand mining hotspots and their underlying drivers. The recurrence intervals of sand mining boats were assessed from 2014 to 2020 using Sentinel-1A, and its association with riverbed incisions were examined from bathymetry field surveys between 2017 and 2020. Our results attest to sand mining intensification from 2015 to 2020, particularly in the upstream section of the VMD, where 70% of the activity was recorded. Not only was there an apparent increase in sand mining hotspots by 32.4%, but most hotspots recorded a recurrence interval of 2 years. This potentially indicates a minimal timeframe of sediment replenishment before the same locations become economically viable for further sand extraction. Additionally, a correlation was detected between sand mining hotspots and significant riverbed incisions, although the lack of spatial overlaps in some regions suggests other upstream influences like bank collapse and river damming. Our study, through the meticulous assessment of sand mining boat movement and river bathymetry data, ultimately sheds light on the potentially unsustainable scale of sand mining activities in the VMD. It aims to support informed decision-making and effective regulations that tackle excessive sand extraction amid the dynamic environmental challenges we face, while offering valuable insights to similar deltas worldwide.

Plant extinction in the Anthropocene

Abstract Species go extinct each day, most without notice. The current human-induced extinction rate is up to 700 times higher than the background rate. Extinctions are not different for plants, animals, or fungi, although botanical and invertebrate extinctions are much more poorly documented than those of charismatic vertebrates. In a recent book on extinct plants (Christenhusz & Govaerts, 2023), an overview of botanical extinctions since 1753 was presented, listing which species became extinct and the probable reason for their extinction. As most have a date when they were last documented, a timeline of extinction can also be compiled based on these data. This timeline shows an increase from 1890 to 1940, but a decline in new recorded extinctions after the 1980s, which is likely a result of taxonomic impediment. Extinction rates before 1800 are impacted by the lack of data (here named Berkeley extinction). It can be concluded that extinction is highest in biodiversity-rich areas with high human influence (extinction hotspots). Two new combinations and a new name are proposed here, showing the importance of taxonomy to conservation. Although anthropogenic plant extinction is a global phenomenon, areas of particular concern are the Hawaiian Islands, southern Africa, Australia, the Indian Subcontinent, Southeast Asia, and Brazil. Extinctions have been mainly caused by land clearing for agriculture and urbanization, invasive feral animals, mining, river dams, diseases, and poaching. We predict that the unusual weather patterns associated with rapid climate change may result in more plant extinctions. Reintroduction, even if a species persists in cultivation, is not always possible due to lack of suitable remaining habitat where threats are decreased or removed. Successful reintroduction cannot be guaranteed. It is costly and usually dependent on short-term funding, after which these efforts may be in vain. Protection of species in their natural habitat is much more cost-effective in the long term. Sometimes, rescued plants should be introduced in similar habitats outside their natural range where the threats are absent. This follows the programmes of assisted migration for climate change mitigation, but this can also be assisted introduction to prevent extinction. Protection of critically endangered species that have naturalized outside their native range should also be considered.

Steady-state semi-analytical solutions for assessing the two-dimensional groundwater hydraulic head depletion induced by river dam removal

Dams are pervasive features of the world’s river systems. The reservoir associated with the dam modifies the distribution of the hydraulic head in the aquifer and the natural groundwater flow. However, such modifications must be defined to forecast their environmental, economic and/or social impacts. Based on the method of fundamental solutions (MFS), steady-state semi-analytical solutions are proposed for evaluating the long-term spatial distribution of the rise or decline of the hydraulic head in an aquifer caused by a dam reservoir on a watercourse or its removal. MFS was chosen because of its ability to account for different boundary conditions along the banks of the watercourse. The dam reservoir can have a triangular or rectilinear geometry. The aquifer is assumed unconfined, homogeneous, inclined and finite. The solutions take into account both the reservoir-aquifer interaction and those between the stream and the aquifer up- and downstream of the reservoir. The reservoir-stream system fully penetrates the aquifer, and is separated from the aquifer by semi-pervious banks (Robin condition). Analysis of the semi-analytical solution included sensitivity tests, and assessment of the influence of several parameters: reservoir leakance parameter, width of the reservoir and width of the aquifer. The results show that the reservoir and river leakage parameters up- and downstream of the reservoir, as well as the geometry of the reservoir dam, are the main determining parameters of the extent of the induced groundwater mound. They show that low aquifer-river exchanges in the river upstream and downstream of the reservoir increases the spatial extension of the mound. The degree of error introduced by the method of linearization used to solve the governing partial differential equation is also discussed. A solution has been also developed with a pumping well, particularly to assess what the depletion of the water level at the well location might be if the dam is removed. The proposed solutions were applied at two field sites, giving satisfactory results.These semi-analytical solutions will be useful applications for assessing the long-term spatial impact on the aquifer of the emplacement, removal or leveling of a reservoir dam.

Dam regulation alters the spatio-temporal delivery of organic carbon along the Yellow River

Global river damming has significantly altered the riverine hydrodynamics and organic carbon (OC) delivery along the Land-to-Ocean Aquatic Continuum (LOAC). The Yellow River, one of the largest rivers in the world, has been under perturbation and fragmentation by dam construction. In this study, we quantified particulate OC (POC) and dissolved OC (DOC) fluxes, on daily-monthly-annual timescales, to explore the effects of dam-triggered perturbations on OC delivery in the Yellow River. We found that the “natural” seasonal delivery of OC upstream of the Xiaolangdi (XLD) reservoir had shifted to a heavily dam-regulated pattern downstream of the XLD reservoir. The dam-oriented Water-Sediment Regulation increased the periodic export of OC to the sea in June and July, as opposed to the natural flood season upstream of the XLD reservoir. The dam-modulated annual and inter-annual export of OC, from the Yellow River to the sea, is also teleconnected by El Niño/Southern Oscillation (ENSO) events. Historically known for its high POC flux, the Yellow River has seen a decline in POC/DOC ratios over the recent decades due to dam regulation. The dam-driven changes in organic carbon delivery along the Yellow River will continue to affect carbon cycling in its estuary and marginal seas.

Response of suspended sediment dynamics to human activities in the transitional zone between Changjiang Estuary and Hangzhou Bay

The Changjiang Estuary and Hangzhou Bay system has experienced river damming and estuarine engineering in the last decades. However, few studies focused on the shifts in its sediment dynamics due to such human activities. In this study multi-decadal development of sediment dynamics in the transitional zone of the two large estuaries was analyzed, based on the synchronous hydrographic data in the winter of 2023, 2014 and 1983. The results revealed significant changes in regional hydrodynamics and suspended sediment transport, despite the continuous good correlations between the current velocity, suspended sediment concentration (SSC), water/sediment fluxes and tidal range. Specifically, the current velocity has been decreased by 8 - 21% after 2014, mainly due to the land reclamation (implemented around 2016) with several groins stretching into deep water and altering alongshore hydrodynamics. The SSC has decreased further by 29 - 38% in addition to the significant decrease during 1983 - 2014. The SSC changes are related to the combination of river damming which induced sediment load reduction and land reclamation which enclosed a large amount of sediment. Furthermore, the sediment transport from Changjiang Estuary to Hangzhou Bay decreased by 36% - 53%, explaining the observed bed erosion in the northern bay mouth in recent years. The findings are also relevant for studies on sediment dynamics in other large estuaries worldwide.

Evaporation from dams governing the water cycle dynamics of a regulated river basin from the Western Ghats: Sharavati, India

Study regionSharavati River, Karnataka, India. Study focusA small mountainous river system, Sharavati, was selected to study the impact of river damming on the hydrological cycle. Sharavati river flow is regulated by two dams, Linganamakki and Gersoppa. Despite the Western Ghats' global significance in controlling local and regional climates, the effects of damming on its hydrological cycles have received limited attention. A stable water isotopic approach was employed in the study. New hydrological insights for the regionThe line-conditioned excess (lc-excess) was primarily negative across all seasons. Notably, the pre-monsoon season exhibited comparatively higher evaporation with high negative lc-excess, while the postmonsoon lc-excess values approached zero, indicating minimal evaporation. The sampling points from the dams exhibited very high evaporation signals, the evaporative loss during the pre-monsoon season from the Linganamakki reservoir was estimated as 10 %, and from the Gersoppa dam was 6 %. Consequently, groundwater sampled near the dams, plotted along the local evaporation line indicating recharge from the evaporated reservoir water. Damming has affected the hydrological cycle of the heavily regulated Sharavati River, transforming the entire catchment into a connected, narrow lake-like structure, especially during the pre-monsoon season. Since the Western Ghat river systems are regulated by many large and small dams, it is pertinent to study the impact of damming on the hydrological cycles of the entire system.

The dynamics of heavy metals and metalloids accumulation in oxbow bottom sediments of the Sok River

The article analyzes the dynamics of heavy metals (V, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Cd, Pb) and metalloids (As, Se) accumulation in the bottom sediments of the low-flow oxbow of the Sok River. This oxbow was formed as a result of the Saratov reservoir creation and located within the Krasnoglinsky District of the Samara city. The study was conducted in 2021 and 2022. Four trial plots were established in the oxbow of the river; the control plot was a sample area allocated in the Saratov reservoir, in the immediate vicinity of the oxbow. The quantitative determination of heavy metals and metalloids content in bottom sediments was carried out using inductively coupled plasma spectrometry. The results obtained showed that specific conditions arise in each research period that affect the studied elements accumulation in the oxbow bottom sediments. These processes are influenced by the location of the sample plot in the oxbow, the flow degree, the spring flood nature, the anthropogenic transformation and the overgrowth of Typha angustifolia L. For all sample plots located in the oxbow, higher concentrations of most of nalyzed elements were detected in 2022. Heavy metals and metalloids accumulated especially actively in the bottom sediments of sample plot 4, located in the oxbow behind an artificial dam and characterized by the weakest flow. The soil cover of Samara city posesses weak and moderate effect on the quantitative characteristics of metal accumulation in the oxbow bottom sediments. Compared to the control, the studied elements accumulated more actively in the bottom sediments of all oxbow sample areas, which confirms the accumulative nature of river oxbow of varying degrees of isolation.

Analysis of Land Use Changes in the Sado Estuary (Portugal) from the 19th to the 21st Century, Based on Historical Maps, Fieldwork, and Remote Sensing

This study analyses land use changes in the Sado Estuary (West-Central Portugal) based on a multi-temporal analysis of 19th century cartographic data and 21st century remote sensing land use maps, updated by fieldwork. A GIS plot of land use evolution is summarized in a quantitative table. The comparison shows the changes in land use, with increasing occupation by human economic activities, including extensive agriculture and forestry, as well as localized urbanization and industrialization. The main elements of the landscape impacted by anthropogenic uses were (i) hydrography—river dams affected the flow dynamics and sedimentary processes in the estuary; (ii) vegetation—increasing agriculture and forestry reduced the area of native vegetation, which is now mostly occupied by vineyards, pine forests and cork oaks; (iii) wetlands—tidal and alluvial plains are being occupied by rice cultivation, aquaculture, industries, and ports; (iv) coastal dunes—new developments are occupying large areas of Holocene coastal dunes; and (v) natural environment—mining and dredging have affected some habitats and biodiversity. This analysis is intended to help the territorial organization of present and future economic activities, as well as to reduce environmental and social problems, thus promoting the long-term sustainability of this rapidly evolving region.

Landslide Damming Threats Along the Jinsha River, China

The 2280 km long Jinsha River has been blocked at least four times in the past 30 years. A landslide damming hazard chain can endanger communities and infrastructures hundreds of kilometers downstream from the damming site in alpine gorges. Past damming events have resulted in severe consequences, demanding a thorough assessment of damming threats along the entire Jinsha River. This study digitizes the Jinsha River and visualizes its topographic, tectonic, hydrologic, and climate characteristics in detail. A two-stage full-probability method is proposed for assessing the damming threats along this river, making it possible to identify potential damming hotspots and high-priority zones for hazard mitigation. It is found that the upper reach of the Jinsha River poses the greatest damming threat, and the threat level gradually decreases downstream. Approximately 33.4%, 36.7%, 20.5%, and 9.4% of the entire length of the Jinsha River are classified as low, moderate, high, and very high threat levels, respectively. Compared with existing hydropower projects, future projects in the upper reach are more likely to be exposed to landslide damming. We highlight the value of basin-scale spatial threat analysis and envisage that our findings will promote more targeted local-scale risk assessments for potential damming hotspots. These outcomes provide the basis for managing the risks of river damming and hydropower infrastructure along the Jinsha River.

A Review of Stability of Dam Structures in Coal Mine Underground Reservoirs

Coal has remained the primary component of China’s energy structure, and high-intensity extraction has continued in the central and western coal-producing regions of China. In contrast to the abundant coal resources, water resources have become extremely scarce in these regions, creating a conflict between coal resource extraction and water resource conservation. The coal mine underground reservoir (CMUR), as a typical technology for combined coal and water extraction and water-preserving coal mining, has been applied in numerous mines in central and western China. This effectively alleviates water resource shortages and achieves the goal of water resource conservation. The CMURs utilizes the goaf created by longwall mining as the water storage space. The reservoir dam structure comprises coal pillars, which serve as protective coal pillars in the mining area, and artificial dam structures that filled the gaps between these coal pillars. The stability of the dam structure under the complex stress effects of hydraulic coupling has been identified as the key to maintaining the safe operation of the CMUR. The mechanical properties, stress field, fracture field, and seepage field (“three fields”) change mechanisms, as well as the research results on size optimization of coal pillar dams and artificial dams in CMURs, were systematically reviewed. The core content included the instability and failure mechanisms of dam structures under the comprehensive coupling effects of factors such as dry–wet cycles of mine water, long-term immersion, chemical effects of high-salinity water, dynamic and static loads, and cyclic loads. This paper is considered to have certain reference value for the study of the stability of dam structures in CMURs and to provide some guidance for the safe operation of CMURs.

Quantitative determination of flow rate variations in reservoir Eco-scheduling: A case study of Yangqu dam in the upper yellow river

Accurate quantification of flow dynamics during reservoir ecological scheduling hinders the maintenance of normal reproductive activities in downstream riverine fish. This study proposed a quantitative method for determining the flow rate changes in reservoir ecological scheduling. The approach utilized the daily flow rate and daily flow-rate increment to characterize the flow process. Adopting the perspective of shifting spawning grounds of adhesive egg-laying fish species in response to flow rate variations, we introduced the Spawning Ground Overlap Rate as an indicator and utilized it to determine flow rate changes. Focusing on the downstream area of the Yangqu Hydropower Station in the upper reaches of the Yellow River, we calculated the distribution of spawning grounds and the Spawning Ground Overlap Rate in the region. We set a threshold for the Spawning Ground Overlap Rate to restrict the flow rate changes. The results indicated that during the fish spawning period, the ecological flow range in the downstream area of the Yangqu Dam was 480–1200 m3/s. It was required to maintain a daily flow rate change of less than 49.45 m3/(s·d) and a maximum seven-day flow difference of less than 227.76 m3/s to maintain the optimal level of spawning ground overlap rate. Additionally, it was necessary to keep the daily flow rate change below 123.83 m3/(s·d) and the maximum seven-day flow difference below 368.84 m3/s to maintain the minimum spawning ground overlap rate. The findings provide foundational data for determining flow dynamics during the ecological scheduling of the spawning period for viscous-spawning fish.