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| Estimation of pollution load from non-point source in Baoxianghe watershed based, Yunnan Province on improved export coefficient model |
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Abstract 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.
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Received: 20 December 2014
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