降雨径流对江淮丘陵区农业流域磷素输出影响研究

选择位于安徽省滁州市城西水库上游的花山流域作为代表性流域,研究江淮丘陵区降雨径流对流域磷素输出的影响。2013—2015三个水文年高频次水量水质同步观测结果表明,流域出口断面径流总磷浓度和输出负荷与降雨、径流变化基本同步。研究期间49%和24%的水样总磷浓度超过地表水环境质量标准(GB 3838—2002)Ⅲ和Ⅴ类标准,水样超标主要发生在汛期雨洪过程。花山流域单位面积年总磷输出负荷分别为0.72、0.91 kg·hm~(-2)·a~(-1)和3.86 kg·hm~(-2)·a~(-1)。汛期和夏季总磷输出负荷占全年的比例分别为94%和80%。梅雨期间或台风雨期间单日磷素输出负荷最大值可达全年负荷的12%～18%。2013年和2015年梅雨时期总磷输出负荷占全年输出负荷约60%;2014年梅雨期总磷负荷输出比例仅占全年负荷的11%,受台风"麦德姆"影响,一次台风雨过程磷素输出负荷占全年负荷的22%。花山流域全年10%的时间内发生的5～10次雨洪过程中,约30%的直接径流输出的总磷负荷约占全年总负荷的50%。流域出口断面TP输出负荷主要受流量影响,建立了基于日平均流量的TP输出负荷预测模型。梅雨和台风雨形成的暴雨径流是江淮丘陵区花山流域磷素负荷输出的主要驱动因子。

Impact of rainfall-runoff on phosphorus export from an agriculture watershed in the hilly region of Yangtze-Huaihe zone, China

Huashan watershed at the upstream of Chengxi Reservoir in Chuzhou City of Anhui Province was selected as the representative agricultural watershed to study the impact of rainfall-runoff processes on watershed phosphorus export patterns in the hilly region of Yangtze-Huaihe transition zone with high water sampling frequency in three hydrological years. Results showed that total phosphorus (TP)concentration and load were almost synchronous with the occurrence of rainfall and runoff. 49% and 24% of the surface water samples exceeded the third and fifth class of National Environmental Standards (GB 3838-2002), which mainly occurred in the rainfall-runoff processes during the rainy seasons. The annual loads of TP per unit area in three hydrological years were 0.72 kg·hm^-2·a^-1, 0.91 kg·hm^-2·a^-1 and 3.86 kg·hm^-2·a^-1. TP load during the wet season and summer occupied 94% and 80% of the annual load respectively. TP load in the plum rain season of 2013 and 2015 occupied 60% of annual load. TP load in the plum rain season of 2014 was only 11% of the annual load, while, 22% of the annual load was exported during the rainfall-runoff caused by the typhoon "Madham" during July 23-25. 50% of annual TP load was exported through direct runoff, which occupied 30% of the annual runoff in 5 to 10 storm runoff events. TP load estimation model could be established based on daily flow. Storm runoff caused by the plum rain and typhoon rain was the main driving force of phosphorus export from Huashan watershed in the hilly region of Yangtze-Huaihe zone.