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| Estimating methods for non-point source pollution of small watershed in drinking water source area |
| Zhang Yan1,Zhang Zhiqiang1,Xie Baoyuan1,Wu Jun2,Wu bin1,Zhao Huijuan1,Zhao Yuanyuan1,Wang Li1,Tang Yin1,Liu En1 |
| 1.Beijing Forestry University,Key Lab.of Soil & Water Conservation and Desertification Combating,Ministry of Education,100083;2.Station for Researching Forest to Protect Riverhead in Beijing,100029:Beijing, China |
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Abstract Nitrogen pollutant in Miyun Tumenxigou small watershed was estimated by export coefficient method,the Universal Soil Loss Equation,Runoff field experiment and relevant relationship method.The results show that: Johnes model of the export coefficient method and the export coefficient model which was considered the rainfall impact on,had large relative error.Considering the loss of watershed the of export coefficients method was the best,of which the simulation value closed to the true one and the relative error was 5%.Export coefficient method is suitable for the region where there is no enough observation data.Export coefficient is the key to improve the accuracy of estimation.The relative error will be smaller if non-point source pollution area are divided into smaller type block and the monitoring results of runoff plot can be used for the whole small watershed.The relative error of runoff plot experiment estimation in Miyun Tumenxigou small watershed reached to 8% by this method.Relevant relationship method needs establish the relationship between pollution load and rainfall,which requires long-term rainfall-water quality monitoring data.Relative error of relevant relationship method was approximate to 4%.Universal Soil Loss Equation did not take into account the transport capacity of runoff,estimation error of which was relatively large.
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Received: 29 April 2008
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