三峡前置库汉丰湖试运行年水体水质现状及控制效果评估

三峡汉丰湖是世界范围较罕见的专为减弱消落带影响而修建的前置库,也是中国最大城市人工湖体,自汉丰湖试运行后,山水林田湖生态效益及建设宜居城市的社会效益显著.本文以三峡汉丰湖为研究对象,对汉丰湖试运行年支流来水及湖体断面进行水文、水质分层监测,包括水文参数(v、H等)、物理参数(T、pH、SD、DO、TSS等)、化学参数(高锰酸盐指数、Chl-a、TN、DN、NO_3~--N、NH_4~+-N、NO_2~--N、TP、DP、SRP等)共17个指标.监测结果表明:1 2月、10月等开始泄水蓄水时期水质较差,南河支流来水断面水质最差,调节坝出水断面最好;2汉丰湖水体总体呈轻度富营养化,主要污染指标为DN、TN、NO_3~--N、TP;3汉丰湖在试运行年对水体富营养化控制效果显著,Chl-a年平均消减率57.73%,高锰酸盐指数年平均消减率28.12%,SRP、TP、TN、TSS、NO_2~--N、DN、DP等年平均消减率20.15%~22.81%,NH_4~+-N、NO_3~--N等年平均消减率16.92%~18.74%,水体年平均富营养化指数降低15.74%.研究表明,1~3月、10~12月高水位湖泊形态试运行期间对各水质指标消减率高于5~8月河流形态时期,汉丰湖试运行良好,对水体富营养化控制效果显著,可消减三峡入库水体污染物浓度.

Hanfeng Pre-dam Commissioning Eutrophication Status and Control Evaluation in Three Gorges Reservoir

To reduce the impact of Fluctuating Zone, the Three Gorges Reservoir pre-dam is rare in the world which is specially designed and is the largest artificial lake body in China. The ecological benefits of landscape, farmland and lake and the social benefits of livable city have been significantly enhanced since the successful commissioning of the Hanfeng Lake pre-dam system. The paper proposed the application of layered hydrology and water quality monitoring for analysis of Tributary runoff and lake body section in the pre-dam commissioning in the whole year, and a total of 17 measured indicators inlucding hydrological parameters such as v, H, etc, physical parameters such as T, pH, SD, DO, TSS etc. and chemical parameters such as permanganate index, Chl-a, TN, DN, NO₃^--N, NH₄⁺-N, NO₂^--N, TP, DP, SRP etc. We found that the water quality was poor during beginning drain and impoundment period and was the worst in tributary inflow section of South River, while the best water quality was located in water section of regulating dam in February and October. The TLI Water Quality Evaluation and factor analyses performed have shown that the water body of Hanfeng Lake was slightly eutrophicated, and the main pollution indicators included DN, TN, NO₃^--N, TP. By the control of pre-dam in three Gorges to eutrophication in commissioning, we found that the average Chl-a reduction effect reached up to 57.73%, the average reduction rate of permanganate index was 28.12%, SRP, TP, TN, TSS, NO₂^--N, DN, DP etc. were on average cut down by 20.15%-22.81%, the average reduction rates of NH₄⁺-N and NO₃^--N were 16.92%-18.74%, and the average eutrophic index of water body was reduced by 15.74%. The highest reduction average rate in lake form period appeared from January to March and October to December, and the lowest in river form period was during May to August.The analysis results showed that the commissioning of pre-dam was good and remarkable for controlling eutrophication, and cutting the concentrations of pollutant water storage in the Three Gorges.