Abstract:The development process of research on the water resources carrying capacity in China is systematically summarized, and it can be divided into five stages: the creation of conception, the preliminary study, the gradual improvement, the difficult development, and the innovation era. On the basis of comparison of research methods, the calculation methods of water resources carrying capacity can be divided into three categories: the empirical formula method, comprehensive evaluation method, and system analysis method. The control objective inversion model(COIM)based on simulation and optimization and its applications are introduced. It is pointed out that research on the water resources carrying capacity in the future focuses on: using the empirical formula method to calculate the national water resources carrying capacity and system analysis method for detailed calculation; constructing the calculation model of water resources carrying capacity and forewarning system platform; studying the dynamic carrying capacity of water resources under the changing environment; and considering the current achievements of water resources regulation and the balance development of water resources and economic society.

Abstract:In order to investigate cumulative water environmental effects of construction of cascaded reservoirs on water environment comprehensively, new understandings of cumulative water environmental effects are summarized from the definition, classification, and characteristics. Common methods for investigating cumulative water environmental effects are compared. Research achievements of cumulative environmental effects of cascade development on runoff, water quality, water temperature, and sediment are reviewed from the aspects of influence scope and main characteristics. New tendencies for future study on the cumulative effects of cascaded reservoirs on water environment are discussed. It is concluded that the study on the cumulative effects of cascade reservoirs in China, mainly qualitative evaluation at present, is in a developing stage. It is necessary to establish a unified evaluation criteria and method in order to systematically investigate the environmental effects of the construction of cascaded reservoirs.

Abstract:Due to the occurrence of strong biogeochemical processes in the lateral hyporheic zone(LHZ), its unique and complex hydrodynamic characteristics play an important role in aquatic ecosystem and ecological environment. Through analysis and summarization of previous studies on the LHZ, the process and mechanism of hyporheic exchange in different directions are clarified, and the main factors(including topographic conditions, characteristics of sedimentary layers, hydrogeological conditions, river engineerings, and riparian vegetation conditions)that affect the lateral hyporheic exchange are analyzed in detail. Furthermore, the effects of lateral hyporheic exchange on solutes, grains, and ecological environments are discussed. Finally, some suggestions on this subject are given for future study.

Abstract:In order to evaluate the modernization level of regional water resources management, an evaluation index system was established from five aspects, including water resources guarantee, water utilization efficiency, water resources protection, public management ability of water resources, and supporting capacity of water resources. The fuzzy analytic hierarchy process(FAHP)and entropy method were used to determine the weights of indices. An evaluation model of water resources management modernization was constructed based on the matter element theory. Using the Gaochun District of Nanjing City as an example, the results show that the water resources management in the Gaochun District was in the preliminary modernization stage, which is consistent with the actual situation and verifies the feasibility and effectiveness of the established evaluation model.

Abstract:To improve the risk management of flood disasters, risk assessment of flood disasters of 1983 and 2010 in Ankang City was conducted using the cloud model. Eight typical indexes were selected to establish an assessment index system based on field investigation. The entropy method was used to calculate the index weights, and the cloud model was introduced to obtain the membership degrees of flood risk. Through conversion between the index weights and membership degrees, the levels of flood risk of 2010 and 1983 were obtained by means of the principle of maximum membership. Results show that the level of flood risk of 2010 increased as compared to that of 1983 in Ankang City, but the risk changes were different in some counties. Areas with high flood risk were mainly concentrated in the Hanbin District and Hanyin County, and the sizes of those areas were almost unchanged. Areas with relatively high or low flood risk increased, while, areas with moderate or low flood risk decreased. The conversion between adjacent levels of flood risk is the natural behavior when the flood risk increases.

Abstract:Based on the three-dimensional numerical model for Lingdingyang Bay of the Pearl River network, the tidal energy flux and dissipation in Lingdingyang Bay under effects of strong wind were analyzed with the method of integration of regional energy dissipation. Results show that the tidal energy transfers into Lingdingyang Bay and the Pearl River Delta through the deep channel. The effects of wind lead to the changes in the amplitude and phase of the tidal energy flux in Lingdingyang Bay, while have insignificant influence on the average energy flux of multiple tides through each cross-section. Strong wind increases the tidal energy dissipation per unit area in Lingdingyang Bay, and the vertical eddy turbulence energy dissipation increases by 1~2 times; however, it does not produce a great change in friction-induced energy dissipation and does not change the spatial distribution of energy dissipation under the effects of landform’s resistances.

Abstract:Based on analyses of the hydrodynamic parameters, turbidity, and temperature of water in the bay of the Meixi River, a typical tributary in the middle area of the Three Gorges Reservoir area, the characteristics of flow at the interface between the mainstream and the tributary during different operation stages of the Three Gorges Reservoir were investigated, and the factors influencing the flow characteristics and the influence of water exchange on the bay are discussed. The results show that the flow is bidirectional in the Meixi Estuary. Driven by the thermal density flow, the inertia of mainstream flow, and changes in the reservoir water level, the flow intensity at the interface and the structure and pattern of the interface between the inflow and outflow differed in different operation stages. The net flux is low(mostly below 100 m³/s), while the water exchange volume(from 314.17 to 535. 26 m³/s, about 4 to 40 times the net flux)is relatively large at the interface in the Meixi River Estuary because of the bidirectional flow. The mainstream inflow could reach the end of the perennial backwater zone even during the low-water level stage with minimum net flux.

Abstract:The wake concentration fields of a cylindrical hydraulic structure with different pollution source locations(upstream and downstream of the structure)were simulated using the Reynolds equation and RNG k-ε turbulence model. The effects of pollution source locations on the distribution of pollutant concentration downstream of the cylindrical hydraulic structure were investigated from three aspects: the time-averaged pollutant concentration, the fluctuation intensity of concentration, and the half-concentration width, which is the distance from the central line of the wake flow to the position with half of the maximum concentration. The results show that with the increase of flow path length, the transverse distribution of time-averaged pollutant concentration experienced three stages, i. e. , the bimodal structure, transition stage, and Gaussian distribution. When the pollution source was located upstream, the concentration fluctuation intensity first increased and then decreased; when the pollution source was located downstream, the concentration fluctuation intensity decreased continuously. The variation of the half-concentration width shows the same trends for the two pollution source locations: a nonlinear increase trend when 1≤x/D<15 and a linear increase trend when 15≤x/D≤30.

Abstract:The hydraulic conductivities of compacted clay at various temperatures were tested with different methods, the improved GDS full-automatic geoenvironmental permeameter(with a flexible wall)and Nan-55 permeameter(with a rigid wall). Results show that the hydraulic conductivity increased with temperature, and they were positively linearly related in a semi-logarithmic plane; the rates of increase of hydraulic conductivity from tests with a flexible wall and rigid wall were, respectively, up to 5.5 and 2.7 times higher at 70℃ than at 20℃. The hydraulic conductivity obtained from the GDS permeameter was larger than that obtained from the Nan-55 permeameter under the same dry density, due to different sample sizes and preparation methods in the two hydraulic tests. Assuming that the viscosity and density changed with temperature, while, the intrinsic permeability of compacted clay was invariable, the estimated hydraulic conductivity varying with temperature agreed with measured results, implying that the change in fluid properties contributed greatly to the increase of the hydraulic conductivity. However, there were certain differences between estimated and measured results of hydraulic conductivity, because the intrinsic permeability changed with temperature in real conditions. For the sample at a confining pressure of 55 kPa, the intrinsic permeability obtained from the GDS permeameter increased significantly with temperature, and the estimated hydraulic conductivity was larger than measured results; while, the intrinsic permeability obtained from the Nan-55 permeameter decreased slightly with the increase of temperature, and there was little difference between the estimated and measured results of hydraulic conductivity.

Abstract:Geomembrane defect-induced leakage may cause potential hazards to an earth-rock dam with geomembrane on the dam surface used for seepage control. Therefore, three-dimensional saturated-unsaturated seepage fields with different sizes of geomembrane defects occurring at different locations on the surface of an earth-rock dam were simulated with the finite element method. The laws of variations of the entire and local seepage fields with different geomembrane defects were analyzed. The seepage behavior induced by geomembrane defects was simulated using the methods of removing defect elements and amplifying the permeability, respectively. Results show that defect-induced leakage has significant influence on the local seepage field near the defects and little influence on other parts of the dam body. With the low position of geomembrane defects, the head at defects will increase, leading to significant increases of the total seepage flow and local elevation of phreatic lines across the defects. Finally, some methods were proposed for control of defect-induced leakage in engineering design.

Abstract:Using the large-scale multiple reservoirs upstream of the Lutaizi section in the Huaihe River Basin as an example, the flood hydrographs of downstream sections before and after construction of reservoirs were compared, and the total impact of multiple reservoirs on the flood hydrograph was analyzed. An approach that adds reservoirs one by one was used to determine the contribution of each reservoir to the change in the flood hydrograph, and the degree of influence of each reservoir was determined. The hierarchical clustering method was used to determine the degree of influence of reservoirs, and the highly important reservoirs were picked out. The results show that large-scale multiple reservoirs in the Huaihe River Basin significantly reduces the flood volume and flood peak of the Lutaizi section, and the time of the peak is changed. The impacts of each of the reservoirs on the flood hydrograph are different. The Meishan, Xianghongdian, Suyahu, Nanwan, Nianyushan, and Foziling reservoirs have significant influences on the flood hydrograph of the Lutaizi section, and are important to flood control decisions in the Huaihe River Basin.

Abstract:In order to verify the feasibility and effectiveness of the whale optimization algorithm for reservoir optimal operation, four test functions were used in the whale optimization algorithm, and the simulated results were compared with those obtained from six algorithms, including the cuckoo search algorithm, differential evolution algorithm, shuffled frog leaping algorithm, particle swarm optimization algorithm, firefly algorithm, and SCE-UA algorithm. The whale optimization algorithm and the six comparison algorithms were used to solve the long-term optimal operation of a single reservoir and cascade reservoirs. The results show that the accuracy of the whale optimization algorithm is higher than that of the other six algorithms by eight or more orders of magnitude, and it has the fast convergence speed, high convergence precision, and excellent ability of optimization. The results of the whale optimization algorithm for the optimal operation of a single reservoir and cascade reservoirs are superior to those of the other six algorithms. The whale optimization algorithm is feasible and effective for reservoir optimal operation.

Abstract:Based on a 21 King ETM+ remote sensing image, time series data of water level variation were interpreted. The water level-area function was derived using the measured water level data of the Sanhe Sluice, a new water level-capacity curve of Hongze Lake was obtained with the integral method, and the water level-capacity curve was compared with the existing curve. The results show that the culture area of the captive polder around Hongze Lake was formed early, and the captive polder condition was improved from 2000 to 2015, but shows an aggravation trend in the western part of Hongze Lake. The selection of the water level-area function has an influence on the calculation of the water surface area with a lower water level, resulting in an error in the calculation of the dead storage of the lake. When the remote sensing image data are more abundant, the difference between lake water levels in different images is smaller, and the water level-capacity curve is more accurate.

Abstract:In order to establish an effective ecological management mode of irrigation and fertilization to reduce non-point source pollution caused by fertilization in paddy fields, nitrogen forms and mass concentrations in surface water and soil water in different soil layers were observed with comparative field trials in an experimental zone in Yuyao City of Zhejiang Province. The variations of nitrogen forms in paddy fields with different irrigation and fertilization modes were analyzed. The results show that in surface water, the average concentration of NH₄⁺-N at seven days after the application of basal fertilizer using the reducing fertilization mode was 46.14% of that using the conventional fertilization mode, while the average concentration of NO₃^--N was 83.62% of that using the conventional fertilization mode. The controlled and mid-gathering irrigation mode coupled with reducing fertilization can prolong the field water storage time, allow nitrogen to infiltrate more rapidly and reserve in the tilth layer, and lead to the improvement of effective utilization of nitrogen, the decrease of the nitrogen concentration in surface drainage, and the decrease of nitrogen deep seepage. High nitrogen concentration of surface water was sustained in four days after fertilization. It is pointed out that drainage should be controlled during this period, so that the loss of nitrogen fertilizer can be avoided and the agricultural non-point source pollution caused by nitrogen fertilization can be alleviated.

Abstract:In order to accurately evaluate the storage capacity of reclaimed land and reasonably select treatment technologies for dredged slurries, based on the theory of sediment transportation mechanics, dredged slurries are divided into three particle-size fractions: d<0.005mm, 0.005mm≤d≤0.01 mm, andd>0.01mm. The variation of relative content for each particle-size fraction was analyzed, and it was determined that the main reason for grain sorting of dredged slurries is the relative movement of particle-size fractions d>0.01mm and 0.005 mm≤d≤0.01mm. Using the sorting coefficient to quantify the significant degree of grain sorting of dredged slurries and the deviation coefficient to quantify the influence of grain composition of in situ mud on grain sorting, the relationships between the sorting coefficient and deviation coefficient and soil properties in reclaimed land were analyzed, and a preliminary quantitative method for grain sorting of dredged slurries in reclaimed land is proposed. The results show that the sorting coefficient decreases with the increase of the distance from the filling inlet and shows a power function distribution, and the significance of grain sorting decreases longitudinally. The sorting coefficient is at its maximum near the filling inlet, where grain sorting is remarkable and the particle-size difference is large. However, it is small near the water outlet, where grain sorting is unremarkable and particle-size distribution is uniform. The deviation coefficient decreases first and then increases longitudinally in reclaimed land, and shows a spoon-type distribution, showing that the soil properties in the forepart and posterior segment of reclaimed land are significantly different from those of in situ mud, but the soil properties in the middle segment of reclaimed land are similar to those of in situ mud. The longitudinal distributions of the sorting coefficient and deviation coefficient are strongly correlated with zoning of soil properties in reclaimed land.