The Distribution Regularity Of Nonpoint Source Pollutants And Drainage Simulation In Hetao Irrigation Area

Non-point source pollution and serious soil salinization is the two big problem of the agricultural production. The main reason of groundwater pollution is the excessive dependence on fertilizers and excessive use of nitrogen and phosphorus, the strong field diving evaporation and imperfect drainage conditions lead to the increasing of soil salinity. Farmland non-point source pollution is uncertain, and the control technology of water pollution is not yet mature.This research background is Hetao irrigation area, under the purpose of reducing non-point source pollution and the salinization degree, based on the inverse distance weighted interpolation method of ArcGIS technology and field drainage model DRAINMOD hydrological module, combined with the typical plots in the irrigation area of yellow groundwater pollutant concentration and the actual drainage situation, explore the regularity of nitrogen and phosphorus pollutants migration in farmland system and the applicability of the DRAINMOD model in Hetao irrigation district, study the correlation of groundwater depth and non-point source pollutants at different periods and the design plan of drain of the farmland, provide reference for the establishment of water pollution control plan for Inner Mongolia Hetao irrigation area.Based on ArcGIS inverse distance weighted (IDW) interpolation,analyze the spatial and temporal variations after the reconstruction of water-saving in Hetao irrigation area, the research shows that:, groundwater depth is deeper, ranging from1.5-2.5m in the irrigation period, the study area southwest corner has high altitudes, the TN concentration is higher, while it is lower in central, TN concentration shows a trend of "northeast high west low"; the groundwater depth shows "south deep north shallow, west deep east shallow" trend in irrigation period, also the TN concentration in the trend of "central lower, south high north low".Choosing Parameter for DRAINMOD model using the field measured data rate in the study area, through the actual operation test shows that:in the study area modeling efficiency coefficient reaches0.76on average, decision coefficient reaches0.82on average, the average relative error is10%and5.9%respectively, proving that the model can be used for local drainage. Different drain spacing have influence on the groundwater depth and the displacement, research shows that:when the drain depth remains the same, with the increasing of drain spacing, groundwater depth decreasing, and the corresponding underground displacement reduced gradually. From the view of suitable depth of groundwater, as the drain spacing increases, groundwater depth increases gradually. Different drain depth affect the groundwater depth and groundwater displacement, the study shows that:when the drain spacing remains the same, the groundwater depth increases with the increasing of drain depth, the underground displacement also will increase. Relative index of drain design for experimental zone has put forward:when drain distance is250m, the depth of the drain chooses200cm; when the drainage distance is500m, the advisable drain depth is250cm. And the displacement of the two schemes respectively7%and4.5%more than that of the actual。...