Reservoir Construction Research Articles

Effectiveness assessment of reservoir projects for flash flood control, water supply and irrigation in Wangmo Basin, China

Most flash floods in countries around the world occur in poor rural mountainous areas and typically cause more casualties and economic losses due to monitoring challenges and early warning difficulties. In mountainous regions, reservoir projects are a very effective measure for mitigating the risk of flash floods and can also be used for water supplies and irrigation, but there is a lack of research on the comprehensive benefit assessments of reservoirs. In this paper, we simulate the inundation extents of flash floods for the Wangmo Basin in China, where flash floods frequently occur, under different return periods using the HEC-HMS (HEC-Hydrologic Modelling System) model and FLO-2D model and compare the resulting housing losses with and without reservoirs. The results indicate that using dam and reservoir operations for flood control in the Wangmo River Basin decreases the flooded housing area in the county centre by approximately 12.9 %–30.2 %, which results in housing losses reductions of 19.7 %–45.7 %.These dams and reservoirs will begin to make a profit during the 38th year of operation, and the average annual net benefit reaches 101.76 million RMB in 50 years, which is equivalent to 1.43 % of the GDP of Wangmo County; the net benefits of flood control, water supply and irrigation accounted for 0.4 %, 1.0 % and 0.03 %, respectively. Priority should be given to planning and building these water conservation measures to help these poor mountainous areas. The construction of dams and reservoirs can contribute to decreasing losses in poverty and disaster-prone regions. The effectiveness evaluation framework for dams and reservoirs presented in this study can be applied to other mountainous basins for flood control and local development.

RETRACTED: Quantifying the effect of anthropogenic activities on water quality change in the Yangtze River from 1981 to 2019

Anthropogenic activities significantly alter the natural hydrological and nutrient cycles, and are recognized as a major influencing factor for water quality deterioration in the river. However, the relative contribution of different human activities, such as fertilizer usage, reservoir construction, and land-use type change, to the water quality pattern of the Yangtze River remained poorly understood. This study investigated the spatiotemporal pattern of water quality in the mainstream of the Yangtze River from 1981 to 2019, identified the dominating influencing factors, and quantified their relative contribution to the water quality change based on the long-term observation data and vector auto-regression model. The result showed that (1) the water quality was relatively poorer in the middle and lower reaches with a wide distribution of farms and construction lands; (2) the water quality experienced a deterioration during 1981–2005 with intense human activities, while it gradually improved during 2006–2019 because of the implementation of environmental protection policy; and (3) the evolution of water quality concentration in the upper reach was primarily affected by natural factors [COD Mn , 43.6%; NH 3 –N, 70.2%; total phosphorus (TP), 55.8%], while in the middle and lower reach, it was mainly driven by fertilizer usage (COD Mn , 29.1%; NH 3 –N, 48.8%; TP, 56.8%) and reservoir construction (COD Mn , 33.0%; NH 3 –N, 40.2%; TP, 42.6%). Our study revealed the spatiotemporal pattern of water quality in the mainstream of the Yangtze River and quantified the effect of anthropogenic activities on water quality patterns, thus helping in the formulation of effective strategies to protect water resources. • Human activity and natural factors contributions to water quality were separated. • Water quality experienced a deterioration while it gradually improved. • Water quality in the upper reach was primarily affected by natural factors. • Water quality in the middle and lower reach was mainly driven by fertilizer usage and reservoir construction.

Spatiotemporal Heterogeneity in Runoff Dynamics and Its Drivers in a Water Conservation Area of the Upper Yellow River Basin over the Past 35 Years

The upper Yellow River Basin (UYRB) is an important water source and conservation area. As well as a warming climate, the region has experienced long-term human interventions, such as grazing, farming and reservoir construction, since the mid-1980s. The runoff dynamics and its drivers in the UYRB remain poorly constrained, especially the differences between pastoral and agricultural areas, due to a lack of detailed measurements. Here, the contributions of climate change, land-use change and anthropogenic water consumption to runoff changes observed at hydrological stations were evaluated by combining the observations with scenarios simulated by a process-based hydrological model. Changes in the pastoral and agricultural areas of the UYRB were then compared at 10-year intervals during the period 1986–2020. The results indicated lower runoff in the UYRB over the past 35 years, when compared with that in the baseline period of 1965–1985, due to the negative influences of both climate change and anthropogenic water consumption. Meanwhile, land-use change had only a weak influence, due to stable land-use patterns. However, spatial differences in dominant drivers of runoff reductions were evident between the pastoral area and agricultural area. Specifically, runoff decreases were caused by the negative influences of climate change in the pastoral area and anthropogenic water consumption in the agricultural area. A shift in the dominant drivers after the period 2006–2015 was attributed to the positive influence of climate change and a weakening of agricultural water consumption and reservoir inflow during the same period. These changes initially caused a decrease in runoff, and later an increase. These findings contribute to a crucial evidence base for optimizing water resource management, ecological protection and high-quality development in the Yellow River Basin.

Contribution to the knowledge of non-native fishes in reservoirs in the Magdalena River basin: the study case Piedras blancas reservoir

ABSTRACT The habitat fragmentation caused by reservoir construction in different aquatic systems in the Magdalena River basin is a latent threat to the diversity of fishes and aquatic environments in the Andean region of Colombia. Contributing to the knowledge about how fish assemblages are formed in these scenarios is fundamental for the management and decision-making on the aquatic resources of the basin. In this communication, we describe the results of a fish characterization in the area of influence of the Piedras Blancas reservoir, a high Andean reservoir built for hydroelectric power generation. Only three species of fish that make up the evaluated assemblage were captured, and two of them, Cyprinus carpio and Xiphophorus maculatus, are not native to the basin. Possibly, with a greater sampling effort, more species can be found. The native species Hemibrycon sp. is distributed mainly in a creek, while in the reservoir, the introduced species dominate. The environmental variables were in optimal ranges for the development of life in the evaluated environments. It is important to advance the knowledge about the distribution of the introduced and native species in the basin to generate recommendations that contribute to the management of these species in the aquatic systems of Colombian Andes.

Challenges in Understanding the Variability of the Cryosphere in the Himalaya and Its Impact on Regional Water Resources

The Himalaya plays a vital role in regulating the freshwater availability for nearly a billion people living in the Indus, Ganga, and Brahmaputra River basins. Due to climate change and constantly evolving human-hydrosphere interactions, including land use/cover changes, groundwater extraction, reservoir or dam construction, water availability has undergone significant change, and is expected to change further in the future. Therefore, understanding the spatiotemporal evolution of the hydrological cycle over the Himalaya and its river basins has been one of the most critical exercises toward ensuring regional water security. However, due to the lack of extensivein-situmeasurements, complex hydro-climatic environment, and limited collaborative efforts, large gaps in our understanding exist. Moreover, there are several significant issues with available studies, such as lack of consistent hydro-meteorological datasets, very few attempts at integrating different data types, limited spatiotemporal sampling of hydro-meteorological measurements, lack of open access toin-situdatasets, poorly accounted anthropogenic climate feedbacks, and limited understanding of the hydro-meteorological drivers over the region. These factors result in large uncertainties in our estimates of current and future water availability over the Himalaya, which constraints the development of sustainable water management strategies for its river catchments hampering our preparedness for the current and future changes in hydro-climate. To address these issues, a partnership development workshop entitled “Water sEcurity assessment in rIvers oriGinating from Himalaya (WEIGH),” was conducted between the 07th and 11th September 2020. Based on the intense discussions and deliberations among the participants, the most important and urgent research questions were identified. This white paper synthesizes the current understanding, highlights, and the most significant research gaps and research priorities for studying water availability in the Himalaya.

Aligning Trends in Climatic Parameters and Nomads’ Indigenous Knowledge about Climate Change in Central Iran (Case Study: Semirom Town)

Abstract Nomadic pastoral communities are considered some of the most vulnerable to climate change. While Indigenous knowledge can play an effective role in mitigating or responding to some impacts of climate change, the extent of their capacity to adapt their livestock and rangeland management is under question. This research aims to assess the scope and applicability of climate change–related knowledge acquired in the management of summer rangeland, with a case study in Semirom, Isfahan Province, Iran. To do so, objective weather conditions (precipitation, minimum temperatures, and maximum temperatures) were evaluated using the Mann–Kendall nonparametric test and compared with subjective evaluations by nomad community members. Specifically, the study targeted a community of 7700 members of the Qashqai, a conglomeration of nomadic tribes in Iran. Their understanding of the weather was evaluated using focus groups and self-administered questionnaires, with a descriptive approach to data analysis. The findings of the climatic investigation revealed a possible shift in the climate in the study area, particularly in winter and autumn. The findings of subjective evaluation showed similar changes in wind, precipitation, and temperature to be the main characteristics of climate change in the region, with about 90% of informants directly citing decreasing precipitation and increasing temperature and wind speeds. The community evaluation also highlighted some adaptations to climate change, such as delays in beginning the seasonal migration, increased reliance on concrete homes, reservoir construction, decreasing livestock yields, and increasing diversification of resources to feed livestock. Understanding the perceptions of nomadic pastoralists, their meteorological basis, and ongoing climate adaptations can facilitate governmental planning.

The charophytes (Characeae, Charophyceae) from the Yenisey Siberia (Russia)

The records of new localities of charophytes from the Yenisey Siberia and confirmations for the ones known before were summarized as a result of study both available herbarium collections and field studies during 2007–2021. The twenty species, including one novel genus and five novel species records, 59 new localities (67 % of its total number), 127 new populations (83 % of its total number) were found in this region. In particular, 12 species (incl. 3 novel ones for the region) are known from the Republic of Khakassia, 17 (7) – from the Krasnoyarsk Territory, 12 (7) – from the Tuva Republic. The genus Chara is the most species-rich and frequent in the area of study. The taxonomic rank of C. arcuatifolia sensu Hollerb. et Krassavina is discussed. It seems to be a morphotype of C. globularis having clearly arcuate branchlets. Nitella tenuissima is a novel species record for Asian Russia. The charophyte northernmost locality on the continent was revealed. It belongs to C. virgata collected at Southern Taymyr. The novel locality of circumpolar species Tolypella canadensis, far distant from ones known before from Komi Republic and Republic of Yakutia, was found in this region too. The species occurrence in different ecoregions was estimated. The contemporary presence of some species after long intervals between observations from their first records was confirmed. The persistence of the same species in the same water bodies after a long period was revealed as evidence of stability of their populations, important for species protection. The loss of charophyte localities as a result of construction of large Krasnoyarskoe and Sayano-Shushenskoe water reservoirs is remarkable. The red lists for the regions studied were compiled and some species were suggested for protection. The important charophyte areas enabling protection of some species were revealed.

Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams

Rich ecosystems such as estuaries and brackish lakes are vulnerable to the effects of human activities and are prone to environmental changes. In particular, the salt environment, which is the backbone of the environment, might be affected not only by direct modifications such as dredging but also in ways that were not initially envisioned. Ichkeul Lake, located in the northern part of Tunisia, is a shallow brackish lake registered as a UNESCO World Natural Heritage Site. The construction of reservoirs upstream of the inflowing river in the 1980s reduced the amount of freshwater inflow. That only had been thought to be the cause of the increase in salinity in Ishkeul Lake. On the other hand, the sedimentation in the reservoirs upstream was remarkable, and the supply of sediment from the reservoirs upstream to the Ichkeul Lake was stopped. Changes in sediment outflow may have reduced lakebed altitude and enhanced seawater intrusion. However, the environmental protection measures for the lake so far have focused only on improving the water budget and have not been quantitatively evaluated for sediment transportation. In this study, we first estimated the water budget of the lake. Then the re-suspension by wind disturbance in the lake was estimated from the correlation with the wind speed based on laboratory experiments and field measurements. The outflow of the sediment estimated with these two models was compared with the sediment volume trapped in the upstream reservoirs that would have flowed into the lake if there had been no construction of the dams. Based on this, we evaluated whether the lake is currently erosive or cumulative. As a result, the estimated annual outflow of sediment to the sea was 4300 tons/year. It was estimated that the construction of the reservoirs upstream changed the trend of lakebed height from accumulation to erosion.

A Simplified Method for Leakage Estimation of Clay Core Dams with Different Groundwater Levels

Clay core dams are widely applied in reservoir construction, regulating water resource and provide electric power. Leakage is a common problem in reservoir construction, and the leakage amount, which not only affects the economic benefits of the project, but also relates to the safety of the dam body, is difficult to estimate. According to Darcy’s law and stable seepage theory, an analytical method can be proposed to calculate the leakage of the clay core dam to gain the seepage flux in a short time. By making some reasonable assumptions, we propose formulae for seepage calculation in different conditions of the position of the groundwater levels, below or above the reservoir bottom. Both sets of formulae contain two parts of leakage calculation, i.e., leakage from the reservoir bottom and leakage from the dam body. By using the proposed analytical method, the leakage of clay core dams can be estimated considering the influence of the groundwater level. To prove the rationality of the analytical method, a simple numerical model can be established using Geo-studio 2020 to calculate the seepage flux of the clay core dam, where relative errors between numerical solutions and analytical solutions are less than 10%. To verify the feasibility in engineering applications, the proposed method was applied to calculate the seepage of a clay core dam in Sichuan, China, which was also calculated using numerical methods by establishing a three-dimensional model. The results show the rationality of the analytical method, which can strike a balance between precision and efficiency.

Spatial-Temporal Change for Ecological Intactness of Giant Panda National Park and Its Adjacent Areas in Sichuan Province, China

Human activities change the natural ecosystem and cause the decline of the intact ecosystem. Establishing an applicable and efficient human activity monitoring indicator system benefits China’s ambitious national park system construction. In this study, we established a refined technique for ecological intactness scores (EIS) and applied it in the area of Giant Panda National Park (GPNP) from 1980 to 2020 by quantifying four types of human interferences including land use and cover change (LUCC), road construction, water reservoir and hydropower construction, and mining. The results show the following: (1) Under the ecological intactness score range of 0–10, the GPNP with about 92.6% area of the EIS was above 6.0, and the mean baseline level of intactness was 7.1 when it was established in 2018. (2) The EIS in the east of Qionglaishan and south of Minshan were relatively lower than the rest of the study area. (3) During the past 40 years, 80% of the GPNP’s ecological intactness has remained stable. (4) In total, 14% of the GPNP was degraded mainly in the areas below 1200 m with severe human activities. (5) LUCC and road construction were the main driving factors for the decrease of ecological intactness in the GPNP. (6) The habitat of the giant panda is mainly distributed in the areas with an EIS above 6.0, and this is a key link between ecological intactness and habitat suitability. Our research proved that the ecological intactness score (EIS) is an effective indicator for monitoring and assessing the impact of human activities on the regional natural ecosystem and could be helpful for ecological restoration and human activities management GPNP in the future.

Influence of Moisture Content on Creep Mechanical Characteristic and Mic-Fracture Behavior of Water-Bearing Coal Specimen

The most challenging aspect of constructing an underground reservoir is ensuring that the safety coal pillar has long-term stability. It is of great significance to study the creep mechanical behavior of coal pillars under water-rock interaction for the construction of underground reservoirs. Five kinds of coal specimens with different moisture contents (dry, 2.42%, 5.53%, 7.55%, and saturated) were prepared. The effect of moisture content on the creep mechanical behavior of coal specimens was studied by graded loading, and the acoustic emission signals during the creep loading of coal specimens were monitored. The results showed that with the increase in moisture content, the instantaneous strain and creep strain of coal specimens gradually increase, and the total time of the creep test, creep failure stress, and long-term strength generally decreases. The creep failure stress to peak strength and the ratio of long-term strength to peak strength were 73%~85% and 57%~65%, respectively, which are basically independent of water content. As the water content of the coal increased, the cumulative acoustic emission energy decreased, and the failure form of the coal specimen gradually shifted from tension failure ( ω = 0 % and 2.42%), tension shear composite failure ( ω = 5.53 % ) to shear failure ( ω = 7.55 % and 10.08%). The research results can be used as a reference for the design and strength evaluation of coal pillars for underground reservoirs in coal mines.

Water Reservoirs as a Driver of Anthropogenic Changes in Landscape and Transport Networks: The Czech Republic Experience

The construction of reservoirs has a major impact on the floodplain landscape, and their existence also affects land use in the hinterland. The aim of this article is to evaluate the influence of artificial lakes on changes in landscape use and transport networks; in this context, an assessment is provided of the significance of this anthropogenic activity as one of the drivers of landscape change. Old topographic maps and archival aerial photographs are used to analyze changes in the use of landscape and road networks, and these materials are complemented with the latest geographic data in digital form. Utilizing geographic information systems, we assessed the landscape changes and processes in the hinterland of those Czech Republic reservoirs that have an area of 100 ha or more. The results of the research show that landscape change processes are more intensive in the hinterland of the lakes than in the surrounding landscape. The predominant utility function of a reservoir emerged as a key factor in landscape use changes and ongoing processes. A different landscape use scenario can be observed in drinking water reservoirs, especially regarding the leisure and irrigation functions that dominate elsewhere. After the completion of reservoirs, the road and railway networks had an impact on, above all, the connection of the nearest villages in the hinterland of the lakes. The information that we found can be employed in projecting future changes in land use and road networks at newly planned dams.

Sensitive indicators of soil nutrients from reservoir effects in the hot-dry valleys of China

The construction of giant reservoirs can affect the hydroclimatic cycles and related soil nutrient recycling. The current understanding of variations in soil nutrients driven by reservoir impoundment is limited because soil often reacts slowly to changes and the impoundment effects can be masked by various factors, making detection difficult. The soils in the hot-dry valleys suffer from a savanna-like hot and dry climate, making it an ideal area for studying the effect of reservoir impoundment on the soil. Here we collected 138 soil samples in April and November along the cascading reservoirs located in the hot-dry valleys of China, including Xiangjiaba, Xiluodu, Baihetan, and Wudongde reservoirs. Results showed that (1) the reservoir impoundment does alter the soil nutrients. The contribution of the impoundment to the variation of soil nutrients was 3.82% in April and 6.44% in November. (2) Compared to April, a relatively dry and cold November is preferred for revealing the reservoir impact on soil nutrients in the hot-dry valleys. (3) Available nitrogen and available phosphorus, followed by soil organic matter, are potential sensitive indicators that can be used to reflect the reservoir impoundment effects. Additionally, pH may be a potential indicator, particularly in the head reservoir area. It is important to note that the effect of reservoir impoundment on soil nutrients is easily masked. This study encourages dam operating agencies, policymakers, and researchers to regard reservoirs as integral parts of the forcings that modify soil nutrients and is an essential step in gaining an insight into the impact of hydropower development on surrounding terrestrial ecosystem services related to soil nutrients.

Mechanical Properties and Acoustic Emission Characteristics of Water-Bearing Coal Specimens under a Coupled Compression–Shear Load

The construction of an underground coal mine reservoir plays an essential role in the ecological environment of arid areas. The moisture content and loading angle inclination significantly impact the strength and stability of the safety coal pillar of underground reservoirs. Water-bearing coal was investigated under a coupled compression–shear load using inclined uniaxial compression tests on coal samples with varying water contents (ω = 0%, 2.42%, 5.53%, 7.55%, and 10.08%) and acoustic emission (AE) technology. The weakening mechanism of the mechanical property parameters and the crack evolution law, combined with the characteristics of the stress–strain curve, the cumulative AE count, and the cumulative AE energy methods, were used. Therefore, the evolution law of the coal’s crack closure (CC) threshold, crack initiation (CI) threshold, and crack damage (CD) threshold was analyzed. The results indicate that coal samples’ peak stress and elastic modulus decreased when the water content or inclination angle increased. Peak shear stress decreased as the water content rose, and the overall characteristics gradually rose as the inclination angle increased. The exception was when the ratio was 10.08%; when the inclination angle was 0°, the failure mode of the coal sample progressively changed from tension failure (ω = 0%, 2.42%) to tension–shear composite failure (ω = 5.53%), and finally to shear failure (ω = 7.55%, 10.08%). When the inclination angle was 5°, the coal sample was dominated by tension–shear composite failure at any moisture content. When the inclination angle was 10° and 15°, the coal specimens showed shear failure at any moisture content. The evolution law of tensile and shear cracks determined by AE characteristic parameters was consistent with the macrofracture characteristics of the coal specimens. When the water content or inclination angle increased, the crack closure threshold, crack initiation threshold, and damage threshold of the coal samples decreased. Therefore, these results show that their peak stress ratio does not depend on the water content or inclination angle.

Monitoring 23-year of shoreline changes of the Zengwun Estuary in Southern Taiwan using time-series Landsat data and edge detection techniques

More than 80% of sandy beaches in Taiwan have been experiencing a severe recession, although the sediment discharge of rivers in Taiwan is significantly higher than the world average producing almost 2% of global fluvial sediment discharge. This contradiction is primarily due to the widespread constructions of reservoirs and intensive anthropogenic activities in coastal regions. In addition, coasts are particularly vulnerable to hazards due to climate change, such as sea-level rise, as they are located at the transition zone of terrestrial and marine environments. Along with the fact that Taiwan is an island and is one of the most climate-vulnerable regions globally, coastal management and sustainability are nationally critical topics, especially considering the ongoing reformation and legislation of Taiwan's coastal conservation laws.As stated in the Sustainable Development Goals (SDGs) goal 14, accurate and continuous shoreline positions information is essential for coastal conservation. However, by reviewing previous global studies and projects commissioned by the Taiwanese government aiming at monitoring shoreline changes, they usually exhibit several limitations, such as limited band selections or conservative band ratio-derived water indices, relying on either manual digitization or simple thresholding methods, focusing on either artificial or smoothly shaped coasts, and using images acquired at considerably different tidal height levels.Therefore, in the present study, a subpixel shoreline extraction approach based on a sustainable cross-generation dataset and a robust edge detection algorithm is proposed. This approach is exemplified by the Zengwun River Estuary located in southwestern Taiwan—Taiwan's most critical coastal preservation region. By quantitatively analyzing the resultant time-series shoreline positions from 1999 to 2021, several hotspots of shoreline recession have been identified: an extreme erosional rate up to −69.4 m year−1 is revealed in the northern sand bank; while the offshore sand bar demonstrates an overall landward retreat rate of −35.4 ± 1.24 m year−1.

A Research on the Ecological Operation of Reservoirs Based on the Indicators of Hydrological Alteration

The conventional reservoir operation strategy considering hydropower production ignores the ecology of the downstream rivers and causes a series of environmental problems. To ensure the sustainable development of a reservoir, the operation strategy should consider both the economic benefits of the power station and the ecological benefits in downstream rivers, the key to which is to select suitable parameters for quantifying the ecological objectives of the rivers and incorporate them into the reservoir operation model. To this end, the ecological index (EI) based on the Indicators of Hydrological Alteration (IHA) was developed to reflect the ecology of the downstream rivers, and a reservoir ecological operation model that takes into account the power generation capacity of the power station and the degree of hydrological alteration was constructed, which can be solved using the Non-Dominated Sorting Genetic Algorithm II (NSGA-II). The results show that the mean EI values increase a lot, from 0.24 to 0.62, after the construction of reservoir, and the optimal reservoir operation strategy in each typical year can reduce the hydrological alteration significantly (the reduction rates of both the abundant and dry water years exceed 20%), while ensuring the hydropower production of the power station (the reduction rates of hydropower production are just 1.64%, 3.15%, and 3.16% for abundant, normal, and dry water years, respectively), which provides a good reference for restoring the natural hydrological situation of downstream rivers.

Pengolahan Air Bersih Berbasis Kebutuhan Rumah Tangga dalam Upaya Meningkatkan Kesehatan Masyarakat di Desa Kandat Kabupaten Kediri

The purpose of this community service activity is to increase awareness of Kandat Village residents through counseling about clean water treatment for household needs. This service method used a hybrid method, namely offline and online. The results of the service show that the community is aware of the need for clean water for health and daily needs. Utilization of infrastructure to facilitate clean water treatment is indicated by the construction of reservoirs. The achievement of fulfilling clean water is expected to have a positive impact, especially preventing the spread of the Covid-19 pandemic by using clean water to implement health protocols.

Meningkatkan Kesehatan Masyarakat Guna Mencapai Tujuan SDGs Melalui Penyuluhan Pengelolaan Air Bersih pada Masa Pandemi Covid-19 di Desa Kalimas Kabupaten Situbondo

This community service aims to increase the knowledge of the residents of Kalimas Village about the importance of clean water management as an effort to improve public health in order to achieve the SDGs goals. the service method uses counseling that takes place offline and online to reduce the spread of Covid-19. The results of the service show that the community understands the importance of clean water for health. The construction of reservoirs is proof of the application of infrastructure that supports clean water treatment. The people of Kalimas Village still need material and non-material assistance to increase the SGDs (Sustainable Development Goals) index according to the government's target.

Study on carbon dioxide emission from reservoirs with different regulation types and its empirical prediction model.

The construction of artificial reservoirs with various regulation types on river is currently an important form of comprehensive utilization of water energy and water resources in river basins. The type of regulation is important in controlling the residence time, which in turn affects the photosynthesis-respiration balance in the water. This process has a significant impact on carbon dioxide (CO2) emissions from reservoirs. In this study, seasonal observations were carried out from September 2020 to July 2021 at five artificial reservoirs in the Qiantang River Basin, eastern China, to reveal the characteristics of CO2 emission from the water-air interface of reservoirs with different regulating types. The results showed that the annual average CO2 emission flux of the studied reservoirs varied significantly, ranging from 4.2 to 155.3mmolm-2day-1 with an average of 48.4mmolm-2day-1, which also had a significant negative correlation with the hydraulic retention time. While downstream of the dam, the annual average CO2 emission flux was quite high with a range of 105.8 to 543.0mmolm-2day-1, averaging 381.6mmolm-2day-1. This is mainly due to the release of water with high-concentration CO2 from the bottom of the reservoir. Additionally, using related data of reservoirs around the world, a CO2 emission model with hydraulic retention time, air temperature, and reservoir age as the primary parameters was developed, which was conducive to evaluate reservoir CO2 emissions on a larger scale and provided theoretical support for effective reservoir management.

Impact of Mountain Reservoir Construction on Groundwater Level in Downstream Loess Areas in Guanzhong Basin, China

An accurate understanding of the relationship between reservoir construction and the dynamic change of groundwater level in downstream areas is of great significance for rational development and utilization of water resources. At present, the research on the interaction between surface water (SW) and groundwater (GW) mainly focuses on the interaction between river and GW. There are few studies on the impact of the reservoir construction on GW level in downstream loess irrigation area. Rainfall, evaporation and climate temperature have a great impact on W level, but the impact of reservoir construction on the GW level should not be ignored in the utilization of water resources. In this paper, a GW flow model under a natural boundary was established by numerical simulation. Taking Heihe Jinpen Reservoir in Heihe River watershed as the research object, the influence of the construction of a mountain reservoir on the dynamic change of GW level in the downstream loess region is studied. By comparing the GW level under the natural state without reservoir construction and the measured GW level after the reservoir was built, the variation of the GW depth in the loess area of the lower reaches in the Heihe River watershed is obtained. The results show that simulation accuracy of the interaction between SW and GW was reasonable; after the Heihe Jinpen Reservoir construction, the mean GW level decrease was about 6.05 m in the downstream loess irrigation area in Guanzhong Basin. It provides a method for the simulation and prediction of SW–GW conversion laws. This study is also of great significance to explore the change law of the water cycle and improve the utilization rate of water resources.