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Effect of hydrologic response unit delineation on the SWAT model results of total nitrogen simulation
Received:October 12, 2018  
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KeyWord:SWAT model;hydrologic response unit;land use;soil type;slope;total nitrogen
Author NameAffiliationE-mail
ZHENG Si-yuan College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China  
WANG Fei-er College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
Zhejiang Provincial Key Laboratory for Water Pollution Control and Environmental Safety, Hangzhou 310058, China 
wangfeier@zju.edu.cn 
YU Jie Zhejiang Environmental Monitoring Center, Hangzhou 310012, China  
DONG Qiu-yi College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China  
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Abstract:
      In the Soil & Water Assessment Tool (SWAT) model, hydrologic response unit (HRU) delineation largely depends on the parameters selected, such as slope, land use, and soil type. Different HRU delineation schemes directly impact the results of the SWAT model simulation. In this study, to achieve a suitable HRU delineation scheme for simulating total nitrogen (TN) export from the East Tiaoxi watershed, 18 HRU schemes in 3 groups with different thresholds of parameters were investigated. Each group included one particular parameter of slope, land use, or soil type that ranged in the threshold from 5% to 30% with the 5% gradient, with the other two parameters remaining at determined thresholds. The Nash-Sutcliffe efficiency (NSE) and the ratio of the root mean square error to the standard deviation (RSR) were used to assess the effect of 18 HRU schemes on SWAT model simulation. Results showed that extensive slope classification was beneficial for reducing the deviation between simulated TN values and observed TN values, whereas the lower thresholds of land use and soil type helped obtain better TN simulation results. The land use threshold had the greatest impact on TN simulation. The optimal HRU scheme was found in the group with 5% land use, 5% soil type, and 20% slope.