| Hydrodynamic is one of the important factors affecting the ecological environment of the lake water. It’s process determines the transport process of substances and energy which in the water, largely determines the macroscopic changes of water quality in process. There are many factors affect water eco-environment, such as velocity, flow rate, depth, lake topography, wind speed and direction. The velocity which can reflect the flow characteristics of water can be used as a comprehensive index to reflect the water hydrodynamic conditions.Lake Dalinuoer is a tapical lake which has no outlet and induced by the ground subsidence of Inner Mongolia Plateau since early tertiary. Today, the lake area is gradually shrinking and become even more serious in recent decades. The area was 213.54km2 in 1999 and decreased to 188.48km2 in 2010. In this paper, the special distribution of temperature, salinity and velocity in Lake Dali was knew by measuring. Then it was analyzed by combining with the hydrogen and oxygen isotopes. The results are as follows:1. In vertical direction, the temperature gradually decreases from the surface to the layer of 1.50m, when it decreases to 15℃ or even lower, then it tends to be stable. Totally the southwest area of lake’s temperature is higher than that in northeast in horizontal direction. The salinity of water is mixed evenly in vertical upward. The surface of lake is impacted greatly by the evaporation and the area of high salinity is wide in horizontal direction. The high value of salinity area is concentrated in the center of the lake and surrounded by low salinity area when the water depth is under 1.50m. The changes of temperature and salinity show a good positive correlation.2. The maximum velocity zone is located in the southwest on the surface of the lake under the influence of wind, then transferred to the spot of G at the middle of the lake, and returned to the southwest due to the friction at the bottom. In the influence of northwest wind, the rate of velocity in the west is greater than the east. Water around flow into the centre of lake and in the northwest area of lake flow from northwest to southeast. There are two main clockwise circulations in the east and south area respectively. The circulation in the east is weak for the existence of island. Lake Dali isn’t affected by the northwest wind in winter. The measured velocity values are lower than the measurement accuracy of flow meter. Then it concludes that the strong wind is one of the main water dynamic conditions of Lake Dali.3. Researches on the spatial distributions of hydrogen and oxygen stable isotopes in the lake base on hydrodynamics. Presented the relationship of δD-δ18O in lake Dali in Sep.2014:δD=5.8648δ18O-20.583(R2=0.997). Isotope values of Lake Dali water are -34.33%～28.06‰ for 8D and -2.56%～-1.07‰ for δ18O, respectively. The values of 8D and δ18O in lake are far higher than that in rivers and wells. Then we can conclude that the lake water is supplied from river water and shallow groundwater. There are good correlations among δD,δ18O, temperature and salinity. Although they all have weak correlations with velocity, which are greatly influenced by the direction of flowing. |
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