基于负荷历时曲线法的东苕溪纳污能力研究

Application of load duration curve to analyze the assimilative capacity of East Tiaoxi watershed

根据东苕溪流域2011—2014年水文数据,以氨氮为控制指标,利用负荷历时曲线法计算流域内4个站点对应控制断面的氨氮纳污能力,解析流域内纳污能力的时空变化规律,并结合实测水质数据探究区域水体的实际受纳污染负荷,得到剩余纳污量。结果表明,流域纳污能力年度变化较大,高纳污能力主要集中在6—9月与3月,其中夏季最大,冬季最小,丰水期流域水体纳污能力分别是平水期的1.7倍、枯水期的2.4倍。从空间分布上看,下游区域纳污能力相对大于上游区域,特别是在枯水区,下游纳污能力是上游的4.8倍。根据污染排放现状计算剩余纳污量,结果显示:除洛舍闸站点外,其他站点剩余纳污量均表现为高流量区>丰水区>中流量区>枯水区>低流量区;洛舍闸站点受非点源污染排放影响,高流量区、丰水区反而表现出低的剩余纳污量。综上所述,利用负荷历时曲线能有效开展水体纳污能力计算与分析,可为流域水污染容量总量控制提供依据。

Based on the hydrologic data of East Tiaoxi watershed from 2011 to 2014, taken ammonia nitrogen as control criterion, we calculated the ammonia assimilative capacity of four areas divided from upstream to downstream by load duration curve, and analyzed spatial and temporal variation of assimilative capacity in the basin. Combined with the actual water quality data, we measured the residual assimilative amount. The results showed that the assimilative capacity fluctuated dramatically with time, and the high assimilative capacity was mainly from June to September and March. The summer had the maximal assimilative capacity while the winter had the minimal one. The assimilative capacity of wet season was 1.7 times and 2.4 times that of the normal season and the dry season, respectively. Moreover, the assimilative capacity in downstream area was higher than that in upstream area, especially in dry condition interval when the assimilative capacity in downstream was 4.8 times of that in upstream. Except Luoshezha station, the residual assimilative capacity of other stations had the same variation, which showed as high flow interval>moist condition interval>mid-range flow interval>dry condition interval>low flow interval. The residual assimilative capacity in the Luoshezha station was low in the high flow interval and moist condition interval because of non-point source pollution. In conclusion, the load duration curve is effective in calculating and analyzing assimilative capacity, and this study provides valuable principles for total capacity control in watershed scale.