For water temperature stratified reservoirs, stratified water intake structures are used to extract surface warm water to reduce the adverse effects of low-temperature discharge on river habitats and ...agricultural irrigation. A physical simulation method has been explored and used to conduct the comparative experimental study on the efficiency of the three types of intake structures: a traditional stoplog gate intake, a stoplog gate with a horizontal curtain and a vertical curtain upstream of the intake. In order to extend the laboratory results to the prototype, a similarity relationship for water temperature stratification was derived based on the principle of equal density stratification Froude number between the model and the prototype, as well as the functional relationship between water density and temperature. The similarity relationship makes it possible to simulate the same prototype density flow under different laboratory water temperature conditions, and this was confirmed through experiments conducted in several months with different water temperatures. Under constant water flow conditions, a stable target water temperature distribution can be formed in the experimental model through continuous stratified heating and real-time power regulation, to simulate the density flow generated by various intake operation in water temperature stratified reservoir. The relationships between the intake water temperature and the reference water temperature at intake depth in reservoir were analyzed to distinguish the difference of water intake efficiency. The experimental results showed that, the traditional stoplog gate has a relatively lower efficiency in extracting warm water affected by the lower edge expansion of the drag layer into the cold water zone below the intake elevation; by setting horizontal curtain to prevent the cold water from climbing below, it is helpful to improve the water intake efficiency; by setting vertical curtain in the upstream area of the intake, the velocity of warm water in the upper part of the drag layer increases, and the intake efficiency has been significantly improved. The above research provides a scientific approach for mechanism research and mathematical model validation of thermal density flow.
According to the investigation materials in the water field of Jiaozhou Bay in May, August and October 1979, this paper studied the rise, decline and changing process of water temperature in the ...surface and bottom waters. Based on the definition and model of Yang Dongfang spatial water temperature variation angle, the results indicated that in the waters from inside of the bay mouth to the around from May to October, the range interval of the Yang Dongfang water temperature variation angle is 1.14°in the surface and 6.27°in the bottom when heated is the surface of a water body; from the waters in the bay mouth to the waters outside, the range interval of the Yang Dongfang water temperature variation angle is 13.49°in the surface and 4.00°in the bottom when cooled is the surface of a water body, which displays the changing process of the water temperature when heated or cooled is a water body.
Water temperature is a critically important parameter for characterizing aquatic ecosystem, particularly in hydrodynamic processes produced by human activities or climate effects in shallow water ...regions (oceanic pasture, tidal currents, upwelling currents, etc.). The variation of water temperature is a slight and slow process, as technology advances, high-precision observation of the spatial and temporal variation of water temperature on 3-D scale is crucial to environmental research and predictions. To address this issue, 3-D water temperature field is reconstructed by coastal acoustic tomography technology and inversion water temperature variations are obtained. A multiacoustic station experiment was conducted in a reservoir in Changsha, China, from March 4, 2022 to March 5, 2022. Two grid-averaged 3-D inversion methods (Lagrangian-least-squares method and improved-Landweber iteration method) with multistation underwater sensing network are processed to reveal water temperature fluctuations. The rotated empirical orthogonal function is used to further analyze and evaluate the sensitivity of temperature variations in the individual spatial grids. In this article, water temperature distribution and dynamic variation process in the whole spatial structure are obtained and discussed using 3-D sound transmission information, and the feasibility of the methods is verified by comparing them with temperature depth sensor array observation results. This study provides high-precision ideas and methods for 3-D water temperature activities of underwater acoustic tomography network in shallow environments.
Lake surface water temperature (LSWT) is an important factor of water ecological environment. In the context of global warming, the LSWT of global lakes generally reveals an upward trend. With a ...continuous intensification of human activities and a rapid expansion of the impervious surface, urbanization has exerted an increasing impact on the environment, so the impact of human activities on LSWT cannot be ignored. Because of the special geographical location, the change of LSWT in plateau lakes has important impacts on climate diversity, biodiversity, and cultural diversity. As a result, it is critical to monitor and model the variation characteristics of LSWT in the plateau area. Based on the data set of natural factors representing climate change and human factors representing human activities, this study proposes a classification of lake types by K‐Means clustering method. At watershed scale, 11 lakes in the study area are divided into three types: Natural Lake, Semi‐urban Lake, and Urban Lake (UL). Based on this classification, the variation characteristics of LSWT for the eleven lakes from 2001 to 2017 are analyzed. The causal relationship and contribution of climate change and human activities to the rise of LSWT are discussed. Results show that (1) from 2001 to 2017, the annual mean of LSWT‐day/night and near‐surface air temperature in the 11 lakes show a warming trend, a significant correlation (R = 0.82, α = 0.0164 < 0.5) and a same periodicity, which indicates that near‐surface air temperature is one of the main influencing factors of LSWT warming in Yunnan‐Guizhou Plateau. (2) LSWT warming trend of UL is more obvious than those of Semi‐urban Lake and Natural Lake, indicating that human activities have more significant impact on LSWT of UL. The main driving factors are the impervious surface expansion and population increase. (3) The influence of human activities on the LSWT in Yunnan‐Guizhou Plateau is becoming more and more significant, and it is also the main factor in causing the deterioration of lake water environment in Yunnan‐Guizhou Plateau.
Key Points
Lakes are divided into Natural Lake, Semi‐urban Lake, and Urban Lake by K‐Means clustering algorithm
LSWT warming rate is dependent on combinations of NSAT and human activities; the average rate of LSWT increased is faster than the rate at which air temperatures increased
Human activity will become the main driving factor of LSWT increasing in the research area
Worldwide riverine thermal pollution patterns were investigated by combining mean annual heat rejection rates from power plants with once-through cooling systems with the global hydrological-water ...temperature model variable infiltration capacity (VIC)-RBM. The model simulates both streamflow and water temperature on 0.5° × 0.5° spatial resolution worldwide and by capturing their effect, identifies multiple thermal pollution hotspots. The Mississippi receives the highest total amount of heat emissions (62% and 28% of which come from coal-fuelled and nuclear power plants, respectively) and presents the highest number of instances where the commonly set 3 °C temperature increase limit is equalled or exceeded. The Rhine receives 20% of the thermal emissions compared to the Mississippi (predominantly due to nuclear power plants), but is the thermally most polluted basin in relation to the total flow per watershed, with one third of its total flow experiencing a temperature increase ≥5 °C on average over the year. In other smaller basins in Europe, such as the Weser and the Po, the share of the total streamflow with a temperature increase ≥3 °C goes up to 49% and 81%, respectively, during July-September. As the first global analysis of its kind, this work points towards areas of high riverine thermal pollution, where temporally finer thermal emission data could be coupled with a spatially finer model to better investigate water temperature increase and its effect on aquatic ecosystems.
To assess the decadal water temperature (WT) changes observed at the center of Lake Kasumigaura, a shallow turbid lake in Japan, we constructed a prediction model for WT. The thermal interactions ...among air, water, and sediment were simulated by a one-dimensional differential equation using hourly observations of meteorological and limnological parameters. The validated model showed good performance (i.e., <1 °C RMSE for the daily averaged WT) for 2012, 2013, and 2015, respectively, in both upper and lower water layers, which were attained by incorporating a physical sub-model regarding the surface water temperature (surface WT). The good description of seasonal, daily, and hourly changes in surface WT obtained with the sub-model was confirmed by the observed and simulated time series. We then quantified and evaluated the trends of the meteorological and limnological parameters influencing WT changes from 1979 to 2015 based on their effects on WT by using the prediction model with the increases in air temperature (AT), solar radiation (SR), wind velocity (WV), and turbidity during that period; then, WT in the former period (1979) was predicted according to the trends and compared with the measured WT. The observed WT changes during the period were quantitatively explained by the compound effects of the parameters' changes, i.e., the AT and SR raising the WT, and the WV and turbidity lowering the WT.
Display omitted
•Construction of a one-dimensional model for water temperature (WT)•Simulation of thermal interactions among air, water and sediments•Validation of good description of surface WT•Determination of decadal trends of the parameters influencing WT•Prediction of WT change using compound effects of these trends•Usefulness of the model confirmed by decadal trend in WT
Water temperature is a critically important parameter for characterizing aquatic ecosystem, particularly in hydrodynamic processes produced by human activities or climate effects in shallow water ...regions (oceanic pasture, tidal currents, upwelling currents, etc). The variation of water temperature is a slight and slow process, as technology advances, high-precision observation for of the spatial and temporal variation of water temperature in three-dimensional scale is crucial to environment research and predictions. To address this issue, three-dimensional water temperature field is reconstructed by costal acoustic tomography technology, and inversion water temperature variations are obtained. A multi acoustic station experiment was conducted in a reservoir in Changsha, China, from March 4th to March 5th in 2022. Two grid-averaged three-dimensional inversion methods (Lagrangian-Least-Square method and Improved-Landweber iteration method) with multi-station underwater sensing network are processed for reveal water temperature fluctuations. Rotated empirical orthogonal function is used to further analyze and evaluate the sensitivity of temperature variations in the individual spatial grids. In this paper, water temperature distribution and dynamic variation process in the whole spatial structure is obtained and discussed using three-dimensional sound transmission information, and feasibility of the methods are verified by comparing with temperature depth sensor array observation results. Our study provides high-precision ideas and methods for three-dimensional water temperature activities of underwater acoustic tomography network in shallow environments.
Floating photovoltaics (FPV) are an emerging renewable energy technology. Although they have received extensive attention in recent years, understanding of their environmental impacts is limited. To ...address this knowledge gap, we measured water temperature and meteorological parameters for six months under FPV arrays and in the control open water site and constructed a numerical model reflecting the water energy balance. Our results showed that FPV arrays caused diurnal variation in water temperature and microclimate. Specifically, we found that FPV had a cooling effect on their host waterbody during the daytime and a heat preservation effect at night, reducing diurnal variation. The diel oscillation of water temperature below FPV panels lagged behind that of open waters by approximately two hours. The microclimate conditions below FPV panels also changed, with wind speed decreasing by 70%, air temperature increasing during the daytime (averaging +2.01°C) and decreasing at night (averaging −1.27°C). Notably, the trend in relative humidity was the opposite (−3.72%, +14.43%). Correlation analysis showed that the degree of water temperature affected by FPV was related to local climate conditions. The numerical model could capture the energy balance characteristics with a correlation coefficient of 0.80 between the simulated and actual data. The shortwave radiation and latent heat flux below FPV panels was significantly reduced, and the longwave radiation emitted by FPV panels became one of the heat sources during the daytime. The combined variations of these factors dominated the water energy balance below FPV panels. The measured data and simulation results serve as a foundation for evaluating the impact of FPV systems on water temperature, energy budget, and aquatic environment, which would also provide a more comprehensive understanding of FPV systems.
•The numerical model is established to assess energy balance of the FPV water area.•The influence of FPV on water temperature and local microclimatic conditions is analyzed.•The meteorological heterogeneity of FPV's impact on water temperature is expounded.•The composition and variation of heat fluxes under the influence of FPV are revealed.
Abstract
Water temperature in the Yangtze River mainstream has been experiencing significant changes due to the climate change and the operation of a series of world-class large dams, i.e. the Three ...Gorges Dam (TGD) and upstream cascade dams (CDs). However, quantitative effects of these factors are not fully known, which hinders our understanding on the thermal regime alterations and further prediction in ecosystem response. Here, we will simulate the riverine water temperature (RWT) variations by building a physics-based model, and quantify the respective impacts from TGD, CDs and climate change through a model-based framework. In the framework, both the dam-regulated hydro-thermodynamic processes and the spatial heterogeneity of the meteorological condition in this large river-reservoir system are thoroughly considered. The results show a fluvial warming of 0.31 °C–0.56 °C/10a in recent three decades, mainly attributed to climate change (44%–80% for different reaches). The dam has caused a substantial seasonal thermal lag, e.g. ∼40 d near the TGD in the dry season, and accompanying severe alterations in the monthly RWT. A reduction of 10% in seasonal RWT range is identified, which is attributed to both dam and climate change.
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