The Study Of Agricultural Non-point Source Pollution Characteristics In The Zulihe Watershed

The study by the Zulihe watershed of loess hilly region as the study area, based on concentration method,had been studied in detail on pollutant sources and pollution levels from two scales which were the big and small watersheds, made a quantitative analysis of pollution load generated by agricultural nonpoint source,explore the relationship between rainfall and runoff and the soil and water conservation measures,constructed water quality pollution model of Zulihe watershed, provide decision-making reference and scientific basis for management work.Made the following main conclusions:(1) Present situation of runoff.The majority of Anjiagou watershed runoff was from slope, farmland, forest land, grassland, waste slope, channel runoff accounted respectively for 38.94%, 25.64%, 9.12%, 26.07%, 0.23%, farmland, waste slope and forest land is the main runoff producing area.The annual runoff of Zulihe watershed was decreasing on overall trend, from 1955 to 1971 was the non-significant reduction on run-off, from 1972 to 1985 was the undulated reduction on run-off, from 1986 to 2000 was the significant reduction on run-off, from 2001 to 2013 was the most significant reduction on run-off.(2) The main pollutants and pollution levels.The main agricultural non-point source pollutants of Zulihe watershed were CODMn、BOD5、NO2-N、NH3-N、TP、F-、TN, most of them came from farmland and forest land, It has contributed in slowly decrease of river water quality pollution. The main pollutants of Zuli river were Cl-、SO42-、CODCr、CODMn、DO、NH3-N、NO2-N、NO3-N、F-、TP、volatile phenol. and the pollution of which got worse with affect by both point source and non-point source pollution. the water quality deteriorated in whole to be inferior classⅤ,the amount of most major pollutants with increased trend.(3) Pollutant attenuation and degradation.During the collection process from Slope to channel runoff, all pollutants are attenuated.attenuation rate TP > CODMn>NH3-N > TN > F->NO2-N > BOD5, TP maximum(57.15%), BOD5 minimum(2.86%); and reservoir storage process, the contaminants are prone to degradation, degradation rate TP>NO2-N>BOD5>CODMn>TN>NH3-N>F-, TP maximum(100%), F- minimum(87.41%).