三峡水库蓄水前后干流总磷浓度比较

Comparison of total phosphorus concentration of Yangtze River within the Three Gorges Reservoir before and after impoundment

为认识三峡工程蓄水对水库总磷浓度的影响,于蓄水前(1998-2002年)和蓄水后(2004-2009年)每月对三峡水库干流5个断面总磷浓度进行监测并对数据进行分析.结果表明,同蓄水前相比,蓄水后水库近坝水体总磷浓度显著降低,至2009年,巴东官渡口断面和坝上太平溪断面总磷浓度比蓄水前分别下降了42.8%和54.9%;蓄水后年内总磷浓度虽然仍是丰水期>平、枯水期,但是越近大坝,这种水期差别越小;蓄水后,库区干流总磷浓度整体上表现为从库尾至库首沿程下降,从涪陵下游的清溪场断面至坝上太平溪断面,总磷浓度下降幅度约61%-65%,尤以丰水期沿程下降最为突出.总磷浓度以上变化特征主要是由于库区水位抬高后,流速减小导致的泥沙沉降.

In order to study the impact of the Three Gorges Project on concentration of total phosphorus（TP）,TP concentration of five sections in Yangtze River within the Three Gorges Reservoir was monitored monthly between 1998 and 2009（impoundment began in 2003）.Results showed that there have appeared new characteristics in spatial and temporal distribution of TP concentration after impoundment.TP concentration of water column near the dam decreased significantly comparing with that before impoundment.For example,the average TP concentration of Guandukou section and Taipingxi section in 2009 decreased by 42.8% and 54.9% than that before impoundment,respectively.TP concentration in wet season was still higher than that in even and dry seasons.Nearer the dam,smaller difference was observed between values in different seasons.After impoundment TP concentration declined from the tail to the head of the reservoir,and it decreased by 61%-65% from Qingxichang section（in the downstream of Fuling） to Taipingxi section（near the dam）.The decrease was prominent especially in wet season.The reason for changes of TP concentration mentioned above was mainly due to sedimentation of sand in the reservoir,which resulted from water level increased and the velocity decreased.