亚深型水库水体季节性分层特征研究

Seasonal Stratified Characteristics of Water Bodies in a Sub-deep Reservoir

【目的】探究亚热带亚深型水库的热分层结构、水质响应特征以及形成机制。【方法】对2018年的长潭水库(位于台州市境内)的水温、溶解氧(DO)、pH和叶绿素a的垂直方向变化进行现场测定和实验室测试。然后分析热分层的季节性物理结构特征,探讨其对于水质的影响。【结果】长潭水库在5—6月为3层结构分层期,7—11月为2层结构分层期。相对水体稳定性(RWCS) 8月最高,为521;温跃层厚度8月最大,占水深的85.19%,强度6月最大,为0.70℃/m。DO的垂直方向分布在7—9月呈现3峰特征,10—11月呈现2峰特征。表层水体在5—9月呈弱碱性,其他月份呈中性,底层水体在7—11月呈弱酸性,其他月份呈中性。叶绿素a垂直方向分布在12月、1月和2月以及6月离散性较大,其他月份呈现单峰特征。【结论】长潭水库全年呈现单循环的混合模式,在分层稳定期内呈现了不同于深水型水库的结构特征。亚深型水库特殊的分层结构对于水体中DO、pH和叶绿素a的垂直方向变化产生了一定的影响。

[Purpose]In order to explore the thermal stratification structure,water quality response characteristics and their formation mechanism of a subtropical sub-deep reservoir.[Method]We conducted on-site measurements and laboratory tests on the vertical changes of water temperature,dissolved oxygen(DO),pH,and chlorophyll a in the Changtan Reservoir(in Taizhou City)in 2018.Then the seasonal physical structure characteristics of thermal stratification were analyzed,and its impact on water quality was discussed.[Result]Changtan Reservoir has a three-layer stratification period from May to June,and a two-layer stratification period from July to November.The relative water column stability(RWCS)was the highest(521)in August,the thermocline was the largest in August,accounting for 85.19%of the water depth,and the intensity was the largest(0.70℃/m)in June.The vertical distribution of DO showed a 3-peak characteristic from July to September,and a 2-peak characteristic from October to November.The surface water was weakly alkaline from May to September,and was neutral in other months,the bottom water was weakly acidic from July to November,and was neutral in other months.The vertical distribution of chlorophyll a in December,January and February,and June was more discrete,and other months showed a single peak characteristic.[Conclusion]The thermal stratified structure of Changtan Reservoir presents a single-cycle mixed pattern throughout the year,and presents structural characteristics different from those of deepwater reservoirs during the stratified stable period.The special layered structure of the sub-deep reservoir has a certain special effect on the vertical changes of DO,pH and chlorophyll a.