基于改进输出系数模型的云南宝象河流域非点源污染负荷估算

本文引入降雨、地形因子(α、β)对经典的输出系数模型(ECM)进行改进,基于1999~2010年云南宝象河流域气象、水文、社会经济等数据,利用改进的输出系数模型(IECM)对该地区(位于滇池的东北部,绝大部分在官渡区内,西北部少部分在盘龙区内)的非点源污染负荷进行估算.结果显示,2008年宝象河流域非点源氮、磷污染的所占比例(分别为74.2%和68.0%)要显著高于点源氮、磷污染的所占比例(分别为25.8%和32.0%).氮污染中,不同非点源的贡献率依次为土地利用类型大气沉降农村生活畜禽养殖;磷污染中,不同非点源污染的贡献率为土地利用类型农村生活大气沉降畜禽养殖.宝象河流域的非点源氮污染比例要高于整个滇池流域,非点源磷污染比例与滇池流域较为接近.与实际观测值比较,IECM对TN、TP负荷的估算值的平均相对偏差分别为15%和-6%,ECM对TN、TP负荷的估算值的平均相对偏差分别为54%和17%.这表明改进的输出系数模型(IECM)提高了结果的准确性,可以为滇池流域的污染(尤其是非点源污染)负荷估算提供参考方法.

Estimation of pollution load from non-point source in Baoxianghe watershed based,Yunnan Province on improved export coefficient model

An improved export coefficient model (IECM) was developed through integrating the precipitation and terrain impact factor into the conventional export coefficient model. Based on the meteorological, hydrological, social and economic data in Baoxianghe watershed from 1999 to 2010, IECM was utilized to calculate the total nitrogen (TN) and total phosphorus (TP) loads. The results indicated that the contribution rates of TN and TP loads from non-point source (NPS) (i.e., 74.2% and 68.0%, respectively) were more than that from point source (i.e., 25.8% and 32.0%, respectively) during 2008. For TN loads, the magnitude order of the contribution of NPS was as follows: land use > atmospheric precipitation > rural life> livestock. For TP loads, the magnitude order was as follows: land use > rural life > atmospheric precipitation > livestock. Also, Contribution rates of TN loads from NPS in Baoxianghe watershed were larger than that in Lake Dianchi watershed, the contribution rates of TP loads from NPS in Baoxianghe watershed was close to that in Lake Dianchi watershed. Furthermore, average relative errors of IECM to estimate the TN and TP loads were 15% and -6%, respective. In comparison, the average relative errors of conventional export coefficient model were 54% for TN loads and 17% for TP loads. It is indicated that the IECM improved the calculation accuracy, and it provided reference information of model selection for the estimation of pollution loads especially that from NPS in Dianchi watershed.