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In order to reduce the negative effect of lowertemperature water released from the intake to the environment in the downstream reach, a selective withdrawal structure will adopted in Glen Canyon Dam. The 3D numerical model EFDC was used to simulate the velocity fields and water temperatures released with surface and lower withdrawal. The numerical results of water temperature released are validated with the measured data. The velocity fields with surface and lower withdrawal indicate that the mainstream of withdrawal water column is located near the elevation of withdrawal intake. Temperatures of water released from the surface and lower withdrawal are simulated for twelve months. The temperatures of water released with a surface withdrawal are effectively enhanced compared with the lower withdrawal.

This paper establishes the physical model of the prototype tailings pond using the similarity theory by taking a heightened and expanded project of tailings reservoir in Chengde, Hebei Province as an example and studies the process and mechanism of partial failure of the tailings reservoir when the drainage system fails by adopting the model test of the dam failure. The result shows that the dam damage can be divided into three categories: soil flow damage, gully damage and collapse damage. In addition, this paper analyzes the reasons for the three categories of damages.

As one of the largest coastal wetlands in northern China, the ecological function of Caofeidian wetland has gradually degraded due to the influence of climate and surrounding environment. In order to regulate and repair the water area of the wetland, it is necessary to study and analyse the historical changes and influencing factors of the water area of Caofeidian wetland This paper extracts the water area of Caofeidian Wetland in 1984~2013 from the images collected by Landsat satellites using the normalized difference water index (NDWI), and analyzes the causes of water area variation in the wetland according to the climate data of Caofeidian Meteorological Station and the Tangshan Statistical Yearbook. The main conclusions are as follows: (1) the water area of Caofeidian wetland had been fluctuating in 1984~2013, showing a slow upward trend. (2) Considering the water area variation and the climate data of Caofeidian Meteorological Station, it is concluded that the mean precipitation of Caofeidian Wetland showed a slight decrease while the annual mean temperature exhibited a slow increase. The correlation analysis reveals that the water area variation is not highly correlated with annual precipitation or annual mean temperature. Thus, the natural factors have a slight impact on the water area variation in Caofeidian Wetland. (3) Based on the water area variation and the data in the Tangshan Statistical Yearbook, the author discovered a prominent growth in resident population in Caofeidian District, and a huge increase in the local aquaculture area. The correlation analysis shows that the water area variation in the wetland is highly correlated with the resident population and strongly correlated with aquaculture area. Because Caofeidian wetland is located in the underdeveloped areas of industry and economy, local people have built a large number of breeding ponds in the wetland, so the main influencing factor of the wetland water area is the breeding area, followed by the permanent population.

In order to reduce the negative effect of lower water temperature released from the intake to the salmon in the downstream of the river, a multi-level intake was adopted in Glen Canyon Dam. Based on three-dimensional numerical model EFDC, this article simulated the water temperature under different discharge and open combination, obtained the effect law of discharge and open combination on temperature of water released. The results show that the temperature released increases slightly with the increase of the single diversion flow rate. The effect on the temperature released is very small when the intake opens in different combinations.