Dam Reservoir Research Articles

Underwater noise measurements of a free-running ship model

ABSTRACT The high background noise and narrow widths of towing tanks, which cause sound wave reflections, make them unsuitable for noise measurements, leading to a lack of published hydroacoustic data. To address this, we developed a free-running test model of the benchmark DTC container ship at a 1/80 scale and conducted hydroacoustic tests in the artificial lake at Istanbul Technical University. The model was remotely controlled to pass a fixed water station equipped with a hydrophone. We present ship noise measurements at three different velocities, noting a strong correlation between the propeller rotation rates from self-propulsion tests and hydroacoustic signals at high speeds. However, accuracy decreases at lower speeds due to background noise interference.

Assessing the impact of climate change and reservoir operation on the thermal and ice regime of mountain rivers using the XGBoost model and wavelet analysis

This study presents an analysis of the influence of climatic conditions and the operation of a dam reservoir on the occurrence of ice cover and water temperature in two rivers (natural and transformed by reservoir operations) located in the Carpathian Mountains (central Europe). The analyses are based on data obtained from four hydrological and two climatological stations. The Extreme Gradient Boosting (XGBoost) machine learning model was used to quantitatively separate the effects of climate change from the effects arising from the operation of the dam reservoir. An analysis of the effects of reservoir operation on the phase synchronization between air and river water temperatures based on a continuous wavelet transform was also conducted. The analyses showed that there has been an increase in the average air temperature of the study area in November by 1.2 °C per decade (over the period 1984–2016), accompanied by an increase in winter water temperature of 0.3 °C per decade over the same period. As water and air temperatures associated with the river not influenced by the reservoir increased, there was a simultaneous reduction in the duration of ice cover, reaching nine days per decade. The river influenced by the dam reservoir showed a 1.05 °C increase in winter water temperature from the period 1994–2007 to the period 1981–1994, for which the operation of the reservoir was 65% responsible and climatic conditions were 35% responsible. As a result of the reservoir operation, the synchronization of air and water temperatures was disrupted. Increasing water temperatures resulted in a reduction in the average annual number of days with ice cover (by 27.3 days), for which the operation of the dam reservoir was 77.5% responsible, while climatic conditions were 22.5% responsible.

Microcystin-degrading bacteria reduce bioaccumulation in Fragaria vulgaris and enhance fruit yield and quality

In Morocco, red fruit production has thrived, primarily utilizing hydroponic methods to control crops, increase fruit yield and quality, and avoid soil-related problems. However, the irrigation of these expansive hydroponic farms relies heavily on water sourced from dams, many of which are contaminated with Microcystins (MCs). To address this contamination issue, ongoing research is focused on discovering effective and cost-efficient biological solutions for eliminating MCs. In this study, we isolate and identify bacterial strains capable of degrading MCs, evaluate the rate of degradation, and investigate how soil inoculated with these bacteria affects the accumulation of MCs in plant tissue. The partial 16S rRNA analyses of three bacterial sequences were conducted, identifying them through NCBI as follows: Ensifer sp. (B1) isolated from soil, Shinella sp. (B2) from a cyanobacterial bloom, and Stutzerimonas sp. (B3) from water. These bacteria exhibited the ability to degrade MCs, with approximately 34.75%, 73.75%, and 30.1% of the initial concentration (20 µg/L) being removed after a 6-day period for B1, B2, and B3, respectively. Moreover, strawberry plants were cultivated hydroponically in a greenhouse for a duration of 90 days. These plants were subjected to extracts of cyanobacteria containing 10 and 20 µg/L of Microcystins (MC), as well as water from an artificial lake contaminated with MC, both with and without the presence of isolated bacterial strains. Among these strains, Shinella sp. exhibited the highest efficacy in mitigating MC accumulation. Specifically, it resulted in a reduction of approximately 1.159 µg of MC per kilogram of root dry weight, leading to complete elimination in the leaves and fruits. The findings also indicated that the inoculation of perlite with the three MC-degrading bacterial strains significantly enhanced growth, photosynthetic pigments, yield, biochemical constituents, and quality attributes of strawberries (p ≤ 0.05). These promising outcomes suggest the potential of this approach for addressing the adverse impacts of crops irrigated with MC-contaminated water in future agricultural practices.

Characterization and Quantification of Dam Seepage Based on Resistivity and Geological Information

Dam seepage significantly poses a serious threat to both the reservoir safety and the ecological health of the surrounding area. Characterizing and quantifying seepage zones is essential for effective risk mitigation and reinforcement measures. In this study, Electrical Resistivity Tomography (ERT) was applied to detect seepage on a reservoir dam. The ERT survey included three survey lines along the dam. The results indicated low resistivity in seepage zones, showing a distribution extending to the deep section in the middle of the dam and shallow section on both sides of the dam. The reservoir water came out to the ground surface in the downstream from seepage zones. Five seepage models were constructed to quantify seepage based on geological information. The models were further modeled based on the ERT results. Simulated results revealed the annual seepage of the reservoir is 78,880.16 m3. However, 75.5% of the total seepage is contributed by a region representing 50% of the dam. This concentrated seepage should draw the attention of future safety monitoring and reinforcement efforts. This study combines geophysics, geological, and numerical simulation to quantify dam seepage. This allows for the development of more scientifically sound solutions for preventing seepage and improving drainage ability in reservoir dams.

Analysing slope dynamics of Kaleköy (Türkiye) dam reservoir with Sentinel-1 SAR time series and Sentinel-2 spectral indices

Analysing slope dynamics of Kaleköy (Türkiye) dam reservoir with Sentinel-1 SAR time series and Sentinel-2 spectral indices

Climate Change Impacts for Multipurpose Reservoir Planning: Basnagoda Reservoir, Sri Lanka

Climate change via rainfall and temperature changes poses threats to water resources. Traditionally, these variations are rarely considered in irrigation infrastructure planning. Integrating climate impacts into early irrigation planning ensures resilience and sustainability.This study aims to assess the climate change impacts on Basnagoda reservoir using a reservoir operation study, system designing and sizing, water use strategies and making recommendations as mitigation and adaptation strategies.This study employed reservoir operation model recommended in the Irrigation guideline, Sri Lanka to assess four climatic scenarios derived from predicted temperature and rainfall changes. Sensitivity analysis included reservoir sizing for the most critical scenario. Mitigation and adaptation methodologies such as 1) Reservoir capacity enhancement 2) Seasonal shifting 3) Conveyance enhancement were analyzed. Reservoir operations currently meet 100% of domestic demand, irrigating total 950 ha annually (380 ha Maha, 570 ha Yala) with environmental flow. Design capacity fulfils 78% of domestic demand, with environmental flow for projected period. The maximum cultivable area at the design stage while providing 25% of design domestic demand is 544 ha in Maha and 680 ha in Yala season. With a 20% rainfall reduction posing the worst scenario, domestic water fulfilment reduced to 20% (Maha) and 19% (Yala). Optimal reservoir capacity enhancement is 15%, expanding cultivable area to 390 ha, while providing 25% of design domestic demand. Conveyance enhancement increases cultivable area from reservoir water by 15%. This study is unique for integrating climate change impacts into reservoir infrastructure planning and design stages.

Enhancement of underwater dam crack images using multi-feature fusion

Underwater dam-crack images captured by remotely operated vehicles (ROVs) often exhibit blurred and unclear features because of the absorption and scattering of water and device shaking. To address these challenges, we propose an underwater crack image-enhancement network (UCE-CycleGAN) that outperforms existing methods on unpaired crack datasets. This network employs multi-feature fusion, incorporating edge maps and dark channels to mitigate blurring and enhance texture details. The blurriness metric and number of matched feature points in the enhanced images improved by 4.12 and 17.11 times, respectively. The mean average precision for detection and segmentation increased by 58.5 % and 39.0 %, respectively, surpassing those of other underwater image-enhancement methods. Furthermore, by integrating YOLOv8 feature recognition and a semantic segmentation network, we developed a real-time automated system (UCADS) for underwater dam-crack detection, thereby expanding the applications of enhanced underwater crack images. The effectiveness of UCADS was validated through field experiments at reservoir dams.

Plankton distribution, abundance, diversity, and its potential in the tropical man-made lakes of Kenyir and Temenggor in Peninsular Malaysia

Abstract. Othman F, Yuslan A, Suhaimi H, Azani N, Kamal AHM, Sah ASRMD, Rasdi NW. 2024. Plankton distribution, abundance, diversity, and its potential in the tropical man-made lakes of Kenyir and Temenggor in Peninsular Malaysia. Biodiversitas 25: 3342-3358. Kenyir and Temenggor Lakes, the largest artificial lakes in Malaysia, are the focus of this study due to their unique ecological characteristics and the limited information available. The study aimed to determine the diversity and abundance of plankton in various habitat ecosystems along Kenyir Lake and Temenggor Lake. The selection of three distinct sampling points, namely sampling point A (coastal zone), sampling point B (lotic zone), and sampling point C (lentic zone), was a strategic decision to ensure a comprehensive representation of the diverse habitat conditions. Samples were collected horizontally using a 30-micrometer-sized plankton net. At Kenyir Lake, thirty-two phytoplankton species were recorded, the major division of phytoplankton, with two hundred twenty-eight individuals belonging to Charophyta (43.75%). For zooplankton, Arthropoda (83.3%) was the highest recorded. At Temenggor Lake, thirty-one species of phytoplankton were recorded. The major division with one hundred sixty-five individuals belonging to Charophyta (32.3%). For zooplankton, the major division with two hundred forty-two individuals belonging to Arthropoda (82.4%). The Shannon diversity index, evenness, and species richness measurements revealed a range of index values due to variation in plankton species due to interaction and habitat conditions. The variation in planktonic abundance in Kenyir Lake and Temenggor Lake was attributed to their habitat preferences due to the freshwater lake's ecosystem's different zones and conditions.

Fate of heavy metals in ecosystems of dam reservoirs: Transport, distribution and significance of the origin of organic matter

In this article, a multivariate analysis of the parameters determining the transport and fate of selected heavy metals in the water - bottom sediment interface was carried out. The studies were carried out in the summer season of 2019 at Nielisz Reservoir (southeastern Poland, Lublin Voivodeship).Finally, a previously unknown factor related to the quality of organic matter was identified. Autochthonous organic matter was shown to promote the accumulation of the studied heavy metals. To date, the significance of the origin of organic matter in the context of the transport and fate of heavy metals in retention reservoirs has rarely been reported in the scientific literature. More than that, this factor was not considered an important component in the process of heavy metal deposition in bottom sediments. However, it turns out that not only the quantity of organic matter, but also its quality plays an important role in the circulation of heavy metals in retention reservoir ecosystems. It was found that autochthonous organic matter promotes the accumulation of the studied heavy metals. It can be assumed that, in a sense, it plays the role of a catenary ("hub") controlling the fate of heavy metals in the water-sediment system. It has also been conjectured that, in a sense, OMS may reflect the potential for heavy metal assimilation by aquatic vascular plants (mainly of the C3 group). Plants with a photosynthetic pathway similar to the C3 group generally have a much lower enrichment in the 13C isotope (δ13C from −38‰ to −22‰). In our case, the lowest δ13C-TOCS value was −24.05‰, and the average for the whole reservoir was −21.53‰. In addition, it was observed that quantitative changes in the isotopic composition of total organic carbon δ13C-TOCS, corresponded with changes in the content of the heavy metals studied in entrapped sediments.

Analysis of Fill Dam Using Finite Element Method and Comparison with Monitoring Results

Nowadays, a detailed safety policy is applied for dams. These policies cover structural safety, monitoring, inspection, safe operation, and emergency plans. For high-risk dams, all these policy elements need to be included in dam safety programs. Deficiencies in embankment dams, which suffer the most damage, can be detected by visual inspection and programmed monitoring of dams. In dams, horizontal and vertical deformation, leakage, pressure, stress, loads acting on structural elements, and environmental factors are generally measured. These behaviors can be numerically modeled to determine the dam behavior. Numerical analysis methods are important for monitoring the safety of the dam. Models created with software such as Plaxis provide information about dam behavior. Although numerical analysis is very important for dams, obtaining the material parameters used in the construction of the dam needed for modeling, recording the construction stages of the dam, not taking the water level change in the dam reservoir instantaneously, and not taking the measurement records of the dam measurement instruments correctly for different reasons constitute problems and difficulties for the analyses. Within the scope of this study, İkizdere Dam in Turkey was modeled with the Plaxis finite element program; the survey and piezometer measurement data taken from the dam were evaluated by comparing with the analysis results; the difficulties and problems encountered in the modeling and analysis phase were stated, and recommendations were made on dam safety and numerical analysis. Thus, in addition to other studies, it was emphasized that it is important for dam engineers to monitor the use of numerical analysis models throughout the entire process, not only in the planning phase but also from the planning phase to the life of the dam, and to keep records of all recording intervals that will be needed in digital analysis models.

Dry deposition fluxes, source, and potential ecological impact of amino acids in the Danjiangkou Reservoir of China's South-to-North water transfer project

As a nitrogen source for biological growth, amino compounds can participate in global nitrogen cycle processes and directly impact ecosystems. Dry deposition samples were collected from September 2020 to August 2021 from the Danjiangkou Reservoir of the South-to-North Water Transfer Project. The dry deposition characteristics of amino acids in the reservoir area were analyzed, their sources were resolved, and the potential ecological impacts were evaluated. The results showed that the dry deposition flux of dissolved free amino acids was 0.48 kg N ha−1 yr−1 and that of dissolved combined amino acids was 1.09 kg N ha−1 yr−1 in Danjiangkou Reservoir. The dominant amino acid fractions were glutamic acid and aspartic acid. Agricultural activities, coal combustion, and primary biogenic particles influenced the amino acid deposition in the reservoir area. The potential source areas for amino acid deposition mainly influenced the northeast, southwest, northwest, and south of the reservoir. The amounts of amino acids entering the water bodies via dry deposition was 85.72 t N yr−1, contributing 0.83 g C m−2 yr−1 of new production to the reservoir water bodies. To summarize, this research depicted that the potential ecological impact of dry deposition of amino acids on artificial freshwater lakes should not be overlooked.

The implications of further reservoir development on the Blue Nile in Ethiopia: trade-offs between hydropower, irrigation and transboundary water security

Abstract We evaluate the implications for Ethiopia and Egypt of two dams that could be built upstream of the Grand Ethiopian Renaissance Dam (GERD), in combination with hypothetical Ethiopian irrigation schemes upstream of these Blue Nile hydropower facilities. Two new dams could increase average annual hydropower on the Blue Nile River from Lake Tana to Khartoum and the Main Nile River from Khartoum to Aswan by almost 50% (30.2 TWh yr−1 to 44.7 TWh yr−1). A system-wide analysis of the expected financial benefits of various development scenarios reveals little financial justification for substantial irrigation withdrawals upstream of the GERD. Withdrawing 5 billion cubic meters annually upstream of the GERD without additional hydropower development would reduce total average annual hydropower generation on the Blue and Main Nile River by 10.9% (3.3 TWh yr−1). If two new dams were constructed upstream of the GERD, withdrawing this volume would cause a 15.2% (6.8 TWh yr−1) reduction. 1 and 5 bcm yr−1 of withdrawals upstream of the three dams would also affect water supply downstream, reducing average annual outflow from Sudan’s Merowe Reservoir by 1.1% (0.7 bcm yr−1) and 6.2% (4.1 bcm yr−1), respectively, and by <1% (0.2 bcm yr−1) and 3.3% (1.8 bcm yr−1) at Egypt’s High Aswan Dam (HAD) Reservoir, respectively. Whilst the annual probability of the HAD storage falling below 60 bcm and invoking its current drought management policy is estimated to currently be 0.085, these two scenarios of upstream withdrawals would increase that annual probability to 0.111 and 0.452 respectively.

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.

Modeling total dissolved gas supersaturation in high dam reservoir using advanced novel bidirectional best-first disjoint aggregating M5-rule based algorithms: An innovative framework for ungauged regions

Total Dissolved Gas (TDG) supersaturation is a critical ecological indicator for assessing water quality downstream of high dam reservoirs. TDG concentration exceeding 110 % can cause gas-bubble trauma in fish, leading to mortality and adversely affecting other aquatic organisms. We used hourly datasets of Water Temperature, Barometric Pressure, Spill from Dam, Sensor Depth, and Discharge to calibrate the Bidirectional Best First (BBF) algorithm for feature selection and ensemble-based models (hybrid of Iterative Absolute Error Regression (IAER), Disjoint Aggregating (DA), Random Subspace (RS), and Weighted Instance Handler Wrapper (WIHW) with M5-Rule) for TDG prediction. The TDG prediction capabilities of these models were compared to those of the Support Vector Regression model using statistical metrics. The study determined that Spill from Dam significantly influences TDG prediction at both stations (30.3 % and 31.9 %), while Barometric Pressure is the least effective variable (13.9 % and 15.6 %. According to the BBF technique, an optimal input scenario consists of Spill from Dam, Water Temperature, Barometric Pressure, and sensor depth. The DA-M5-Rule model with root mean square error (RMSE) = 4.00 %, and uncertainty coefficient with 95 % confidence level (U95%) = 11.00 had the highest predictive power followed by IAER-M5-Rule (RMSE=4.41 %, U95%=12.16), WIHW-M5-Rule (RMSE=4.42 %, U95%=12.17), RS-M5-Rule (RMSE=4.61 %, U95%=12.23) and SVR (RMSE=5.71 %, U95%=15.00) at the testing stage, while for generalization stage DA-M5-Rule model (RMSE=4.21 %, U95%=11.08) had the highest generalization power, followed by RS-M5-Rule (RMSE=4.22 %, U95%=10.90), IAER-M5-Rule (RMSE=4.30 %, U95%=11.40), WIHW-M5-Rule (RMSE=4.36 %, U95%=11.44), and SVR (RMSE=5.00 %, U95%=13.50). The relative deviation of the developed models varied between 0.20–0.78 % during the testing stage and 1.72–2.00 % during the validation stage. Developed models in the current study can be applied as a promising tool across the USA. In addition, these models can be used to precisely predict TDG worldwide, particularly after evaluating its generalization power beyond the USA.

Present status and future prospects of fisheries of Tehri dam reservoir

Fisheries in India are a burgeoning industry with immense potential and opportunities. Ironically, because of its enormous but untapped potential, reservoir fisheries are called as "a sleeping giant". The average productivity from these reservoirs in India is about 30 kg/ha compared to the production potential of 250 kg/ha. Inadequate management leads to low rate of fish production in Indian reservoirs. A major impediment to science-based fish productivity in reservoirs is the lack of authentic data on target stocks. Inland fisheries, like those in reservoirs, are particularly affected. Investigators generally rely on simple catch statistics and hypothesis statements to assess fish production and potential yields due to inadequate resources, population data, and experts in the area. The present paper emphasizes the quintessential 44sq km huge Tehri hydro-power dam reservoir, located in the Bhagirathi and Bhilangana valleys of the lesser Himalayas in the Garhwal hills. On average the fish productivity from Tehri reservoir in the year 2021-2022 is reported as 13.75 kg/ha but, this is significantly lower than its actual productivity. Thus, the current technical paper addresses this issue by condensing and synthesizing the current status of fisheries in the Tehri Dam reservoir with past status in terms of fish species diversity. It provides baseline information on fish production and various data shortfalls in fisheries activity management. The paper also describes the ecological and economic aspects that affect fish catch to utilize the reservoir resources and mired the cold-water fishery management in the Tehri reservoir.

A Multifunctional Project Study for Elazig: Botanic Park, Pumped Irrigation Line, and Solar-Hydroelectric Power Plant

Urban centers serve as more than just hubs of economic activity; they are also focal points of community life and social interaction. It is incumbent upon local authorities to elevate the standard of living within these urban environments by establishing communal spaces conducive to enhancing the well-being of residents. To this end, botanical gardens and recreational areas have been established in numerous developed cities worldwide. These amenities not only enrich the lives of inhabitants and local fauna but also constitute significant contributors to the municipal economy. Recognizing their pivotal role in urban economies, the imperative lies in implementing projects that optimize the utilization of available water resources. The prospect of establishing such a facility in the heart of Elazig holds promise. This study undertakes a preliminary assessment of the feasibility of establishing a botanical garden within the designated area, exploring avenues such as tapping into the Keban Dam reservoir, constructing a micro-hydroelectric power plant utilizing downstream water, and other potential initiatives

Beyond dams: Assessing integrated water storage in the Shashe catchment, Limpopo River Basin

Study regionThe Shashe catchment, Limpopo River Basin, Botswana, and Zimbabwe. Study focusThe Shashe catchment is the third largest flow contributor to the Limpopo River Basin. Water availability in the Shashe catchment is highly seasonal due to high seasonal rainfall variability. The seasonality and inter-annual variability cause shortfalls (demand exceeds the average water availability) in certain months and years. Storage is needed to bridge the seasonal water availability “gap” and mitigate the deficits in drought years, i.e., inter-annual variability. While the need for water storage through grey infrastructure such as dams has long been known, there is growing recognition of the need for approaches to water storage that capitalize on all storage types. However, the current capacity to plan in ways that utilize all storage types is limited. The analyses conducted for this paper assessed the volume and spatial and temporal variability of different storage options – large and small dams, sand dams, soil moisture, and aquifers – in the Shashe catchment of the Limpopo River Basin. An integrated SWAT-MODFLOW model and remote sensing approach were developed for 2015–2020. New hydrological insights for the regionThe total annual water storage in the Shashe catchment is approximately 44,000 Mm3, dominated by groundwater. The annual storage is about 42,000 Mm3 in aquifers, 1500 Mm3 in soil, 700 Mm3 in large dam reservoirs, 45 Mm3 in small dams/ponds, and 0.13 Mm3 in sand dams. There is high seasonality in water storage availability. Soil moisture storage is at its maximum from January to March and lowest from July to September. Dam storage is at its maximum from March to May, and the water storage is relatively stable throughout the year. Aquifer storage is relatively stable during the dry seasons compared to other storage options. Optimizing water use considering the seasonal variation in different storage types could improve water availability and climate resilience.

Study on the influence mechanism of interfacial inclination angle on the mechanical behavior of coal and concrete specimens

In recent years, the proposed distributed underground reservoir technology has attracted a lot of attention from experts and scholars in the field of engineering. This technology not only avoids the waste of mine water resources, but also realizes the rational utilization of coal mine underground space, and promotes the green and sustainable development of coal mining. As a storage facility of the underground reservoir, the stability of the coal-concrete composite structure will directly affect the long-term safe operation of the underground reservoir. In light of this situation, this study conducted uniaxial compression and acoustic emission experiments on coal-concrete specimens with interface inclinations of 0°, 15°, 30°, 45°, 60°, 75°, and 90° to investigate the impact of interface inclination on coal-concrete specimen stability. The test results show that the stress-strain curve passes through three stages: compression, elastic deformation, and deformation failure. The peak stress, peak strain, and elastic modulus exhibit a “U”-shaped distribution with varying angles, reaching a minimum at 60°. Crack analysis using RA-AF reveals that tension cracks predominate at 0°-30°, while shear cracks predominate at 45°-90°. The application of the Mohr-Coulomb criterion to coal-concrete specimens is discussed, and a derivation of the formula for calculating the ultimate principal stress is provided. The research in this paper provides a theoretical reference for the structural design and parameter selection of underground reservoir dams in coal mines.

Carbon dioxide emissions from temperate reservoirs and pit lakes of different trophic states

The abundance of human-made inland waters, such as artificial ponds and reservoirs, has multiplied over the last decades. Compared to natural lakes, reservoirs and retention basins can exhibit a higher accumulation of organic carbon and a higher emission of greenhouse gases. Magnitude and dynamics of related emission fluxes are important to understand the role of inland waters in the global carbon cycle. However, origin and use of artificial waterbodies are diverse, and it is unclear whether current gas flux estimates adequately represent all important types and conditions of artificial inland waters. This study compares drivers of CO2 and CH4 emissions from two types of temperate artificial waters that are widespread in central Europe: reservoirs and artificial lakes in former open-pit lignite mines (pit lakes). We measured CO2 exchange at the water surface, calculated surface water CO2 from long-term DIC and pH data, and measured CO2 and CH4 concentrations throughout the water column. We found that an older, eutrophic pit lake showed seasonal variations in CO2 fluxes including uptake during summer and release during turnover, similar to three studied freshwater reservoirs. In contrast, reacidification and repeated addition of carbonate (liming) led to sustained CO2 supersaturation in a young, oligotrophic pit lake throughout the year, potentially making it a steady source of CO2 to the atmosphere. This implies that on an annual level, pH regulation and lake maturity largely determine whether pit lakes act as sources of CO2 (young, slightly acidic) or sinks of CO2 (older, neutral pH).

Spatial differences of dissolved organic matter composition and humification in an artificial lake.

The depth-dependent dynamics of dissolved organic matter (DOM) structure and humification in an artificial lake limits the understanding of lake eutrophication and carbon cycling. Using fluorescence regional integration (FRI) and parallel factor analysis (PARAFAC) models to analyze the 3D fluorescence spectroscopy dataset, we revealed the depth-dependent structure and vertical distribution of DOM in the estuarine and center regions of Lake Hongfeng. The percentage fluorescence response (Pi,n) showed humic acid is an important part of DOM in Lake Hongfeng. Fluorescence results show that the fulvic-like and protein-like materials in HF1-DOM located at the estuarine position showed greater variation in the middle stage, probably due to human influence and sediment suspension. Fluorescence index (PI+II+IV,n/PIII+V,n and FIC4/FIC3) can be used to indicate the degree of humification of DOM in artificial lakes. Results of each index show that the estuary is more affected by human activities, and the humification degree is significantly lower than that of the center of the lake. The evaluation index system of the humification degree of artificial lake established in this study can effectively predict the eutrophication state of the typical area of artificial lake and deeply understand the possible important influence of human activities on the carbon cycle of lake.