水库温排水增温模拟及其对富营养化影响分析

The Simulation of Reservoir Water Warming by Thermal Discharge and Research on Reservoir Eutrophication

温排水导致的水库增温及衍生富营养化是水库生态学领域的研究热点。以承纳温排水的北方某浅水水库为例,利用MIKE21模型构建平面二维水温模拟模型,针对可能出现的调水量和气温极端情况,设定4个情景,分别模拟不同情景下水库水温时空分布规律,对温升带来的富营养化及水华爆发风险进行了分析。结论如下:(1)受温排水口位置、温排水流向及水深共同影响,水库水温呈西高东低,北高南低的分布规律;(2)气温对水库水温的影响较水深更为强烈,取水口1处水域年均温升最大,取水口1和取水口2处水域温升波动较大;(3)调水量和气温等条件变化会导致水华爆发风险变化:除取水口2附近水域外,相对于情景1,情景2和情景3高风险发生时间提前一个月;情景4增温幅度较大,导致东支和取水口1附近高风险延续时段比情景1短一个月。

Reservoir water warming and eutrophication caused by thermal discharge is a hot issue in the field of reservoir ecology. A shallow reservoir in North China receiving warm-water discharge was chosen as the study area, and MIKE21 was used to construct a two-dimensional water temperature model. In view of the extreme conditions of air temperature and water transfer, four scenarios were set to simulate the tem- poral and spatial distribution of water temperature. The eutrophication and risk of algal bloom were analyzed under the four scenarios. The following conclusions were reached.（ 1 ）The water temperature in western and northern water area was higher than that in eastern and south- ern water area, respectively. The main influencing factors were the location of warm-water discharging spot, flow direction of warm water and water depth. （2）The influence of air temperature on water temperature was more significant than that of water depth, and the annual mean wa- ter temperature rise in water intake 1 was the greatest, meanwhile the water temperature fluctuation in water intakes 1 and 2 was relative]y obvious. （3）The change of air temperature or transferred water volume would change algal bloom risk：under scenarios 2 and 3, the occurring time of high risk of algal bloom was one month earlier than that under scenario 1; under scenario 4, the duration of high risk of algal bloom near the eastern boundary and water intake 1 was one month shorter than that under scenario 1, owing to the higher water temperature rise.