乌梁素海水体交换特征及影响因素分析

Characteristics and Influencing Factors Analysis of Water Exchange in the Wuliangsuhai Lake

乌梁素海作为我国北方地区重要的生态安全屏障,多年来面临着湖泊水环境污染、水生态退化等问题,科学开展湖泊水环境综合治理需要以充分掌握湖区水体交换特征为基础。利用2019年4月1日~11月30日乌梁素海逐日水文、气象数据,基于EFDC模型构建了适用于乌梁素海宽浅型湖泊的二维水动力数学模型,引入水龄概念对湖区水体交换特征进行描述,开展了湖区水体交换受植被、生态补水和风场影响的研究。结果表明,乌梁素海湖区水龄在10~275 d之间,水龄表现为小海子>东大滩>出水区>湖心区>进水区;考虑植被情况下,小海子、东大滩平均水龄上升46.7%、25.1%,进水区、湖心区和出水区平均水龄分别下降63.2%、16.7%、4.3%;生态补水量对入湖排干附近水体交换存在明显影响,但影响范围有限;风场是湖区水体交换重要的驱动力,风向变化对湖区环流方向产生影响,风速变化对湖区的流速产生较大影响。

As an important ecological security barrier in northern China,the Wuliangsuhai Lake has faced many problems such as water environment pollution and water ecological degradation for many years.Scientific comprehensive management of lake water environment should be carried out on the basis of fully grasping the characteristics of water exchange in the lake.Based on the daily hydrological and meteorological data from April 1st to November 30th in 2019,a two-dimensional hydrodynamic mathematical model suitable for the wide and shallow lake of the Wuliangsuhai Lake was established by using the EFDC model.The concept of water age was introduced to describe the characteristics of lake water exchange,and the impact of vegetation,ecological water supplement and wind field on water exchange was studied.The results show that the water age of the Wuliangsuhai Lake was between 10 d and 275 d,and the water age of different lake regions was ranked as Xiaohaizi>Dongdatan>outflow area>central lake area>inflow area.Under the influence of vegetation,the mean water ages of Xiaohaizi and Dongdatan increased by 46.7%and 25.1%,respectively,while the mean water ages of the inflow area,the central lake area and the outflow area decreased by 63.2%,16.7%and 4.3%,respectively.Ecological water supplement had obvious impact on water exchange near the inflow area,but the affected area was small.Wind field was an important driving force for water exchange in the lake area.The change of wind direction has impact on the circulation direction,and the change of wind speed has a great impact on the flow velocity in the lake area.