|WU, YONG - Inner Mongolian Agriculture University|
|SHI, XIAOHONG - Inner Mongolian Agriculture University|
|LI, CHANGYOU - Inner Mongolian Agriculture University|
|ZHAO, SHENGNAN - Inner Mongolian Agriculture University|
|PENG, FANG - Hetao University|
Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2017
Publication Date: 2/27/2017
Citation: Wu, Y., Shi, X., Li, C., Zhao, S., Peng, F., Green, T.R. 2017. Simulation of hydrology and nitrate transport in the Hetao irrigation district, Inner Mongolia, China. Water. 9(3):169. doi:10.3390/w9030169.
Interpretive Summary: Agricultural activities in the Hetao irrigation district have contributed to the degradation of aquatic ecosystems and water quality causing severe eutrophication. Ulansuhai Lake has attracted public attention as the most rapidly degrading lake in China. Thus it is important to understand the agronomic, hydrologic and pollutant transport processes in the Hetao watershed which has about half mountainous topography and half agricultural plains. The objectives of this study were to simulate monthly stream flow, total nitrogen (TN) and total phosphorus (TP) in the entire Hetao irrigation district catchment using the Soil and Water Assessment Tool (SWAT) and to evaluate the nutrient load, source areas, and hydrological pathways. The SWAT model captured the temporal variation of streamflow well, and about half of the variations in TN and TP loads. Predicted monthly TN load was correlated with irrigation, whereas monthly TP load was correlated with precipitation. This indicates that nitrogen transport is primarily associated with groundwater flow in the irrigation district, and the timing of agricultural management operations plays a role, while phosphorus is primarily transported with sediments caused by rainfall erosion. Therefore, we conclude that best agricultural management can effectively reduce the nitrogen losses, and buffer strips could prevent the phosphorus transport.
Technical Abstract: Intensive agricultural activities in the Hetao irrigation district have severely degraded local aquatic ecosystems and water quality, and Ulansuhai Lake is now the most rapidly degrading eutrophic lake in China. A better understanding of the hydro-agronomic and pollutant transport processes in the area is thus urgently needed. This study simulated monthly streamflow, total nitrogen (TN) and total phosphorus (TP) for the Hetao irrigation district using the Soil and Water Assessment Tool (SWAT) to evaluate the nutrient load, source areas, and hydrological pathways. The Nash-Sutcliffe efficiency (NSE) values obtained for the streamflow simulations were 0.75 and 0.78 for the calibration and evaluation periods, respectively. The SWAT model captured the temporal variation in streamflow (R2 > 0.8) for two periods; the NSE values for the TN and TP loads were 0.63 and 0.64 for the calibration period and 0.48 and 0.42 for the evaluation period, respectively. The predicted monthly TN load was correlated with irrigation (r=0.61) and the monthly TP load with precipitation (r=0.89), indicating that nitrogen transport is primarily associated with groundwater flow and phosphorus is primarily transported by sediments caused by rainfall erosion. Better agricultural management could thus reduce nitrogen losses, and buffer strips could minimize phosphorus transport.