三峡水库库首水温监测及初步分析

WATER TEMPERATURE MONITORING OF THE HEAD OF THE THREE GORGES RESERVOIR AND PRELIMINARY ANALYSIS

水温是评价水库水生态系统影响的重要水质参数之一，为研究三峡水库库首水温分布状况，于201i年在距三峡大坝约为3．5km处，对三峡水库建成后各个运行期库首水温进行了详细监测。研究发现：在已确定的三峡工程常规调度运行方式下，12～4月库首底部形成明显的低温区域，3月表层和底部水温之差为全年的最大值2．08℃，最大温度梯度为0．156。5月底部低温区迅速减弱，表层和底部水温之差小于1．O℃,6～9月期间，低温区一直处于减弱的趋势，水体垂向掺混逐渐增强，库首水温垂向分布基本均匀一致。但进入10月后，由于上游来流水温较低，水体由于密度较大而潜入底部对低温区域起到了加强的作用，致使表底层温差达到I．46℃。根据2012年3～5月对三峡水库库首茅坪断面水温监测数据可知，在横向断面上，水温几乎没有差别。在分析三峡水库库首水温空间分布时，可以近似认为其横向水温分布基本一致。为研究三峡大坝的建成对河道水温的改变以及坝前是否存在水温分层现象提供依据和参考。

Water quality situation and water temperature distribution will influence not only water ecological environment structure of the front of the dam,but also water quality of the downstream of reservoir,aquat ic microorganism and fish breeding growth. Water temperature is one of the important water quality param eters to assess reservoir water ecological system. For studying the water temperature condition of reservoir head of the Three Gorges Reservoir （TGR）,the monitoring section was set away from the Three Gorges Dam approximately 3.5 km in 2011 ,and water temperature of the reservoir head was monitored detailed in each operating period after the completion of the Three Gorges Project （TGP）. Research found that under the established routine scheduling mode of operation of the Three Gorges Project,the bottom of the reser voir head formed obvious low temperature area from December 2011 to April 2012, water temperature difference between the surface and bottom reached to annual maximum 2.08℃ and maximum temperature gradient was 0. 156 in March 2012. The low temperature area of bottom was rapidly declined,and water temperature difference between the surface and bottom was less than 1.0℃ in May. From June to Septem her,the low temperature area showed a subdued trend,water vertical mixing gradually enhanced,and water temperature vertical distribution of reservoir head was basic uniform. But in October, because of the low temperature of upstream inflow,the water of higher density dived into the bottom resulting in low tempera ture area strengthened,and brought about water temperature difference of the surface and bottom reached to 1.46℃. In the head of the Three Gorges Reservoir,water temperature condition and structure type were different from one another in different operation period. According to the observation findings, water tem perature showed no stability phenomenon at present in the head of the Three Gorges Reservoir. In addi tion,according to water temperature monitoring data of Maoping section from March to May 2012,water temperature of lateral section was almost uniform. The result indicated that water temperature distribution of lateral section was the same basically. Based on the measured data of Mao ping section in the head of the Three Gorges Reservoir from June 2011 to May 2012 ,water temperature structure of the head of the Three Gorges Reservoir in different operation period was also analyzed. This paper could provide basis and refer ences to the research on the channel water temperature changed by the completion of the Three Gorges Dam and whether the water temperature stratification exists in front the dam .