Analysis And Evaluation Of Water And Soil Environment In Guangli Irrigation District In Henan

China is a large agricultural irrigation country.The irrigation area is an important infrastructure for my country’s agricultural and rural economic development,and an important production base for agricultural products in my country.It not only undertakes the important task of water supply for urban and rural life,industry and ecological environment,but also ecological environmental protection and construction.An important area of the beautiful countryside.However,in recent years,the water and soil environment of the irrigation area has been threatened due to the unreasonable development of the irrigation area.For example,the excessive use of chemical fertilizers and pesticides,and the disorderly discharge of domestic sewage and industrial wastewater have destroyed the water environment and soil environment of the irrigation area.This paper takes the Guangli Irrigation District in Henan Province as the research object.Aiming at the characteristics of small water volume,frequent drying up of rivers,and complicated drainage systems in northern irrigation areas,the main canal and main drainage ditch water quality and field soil sampling tests were carried out from 2019 to 2020,and analyzed The water quality and eutrophication status of the main canal of the irrigation area,the soil quality status of the irrigation area,and the temporal and spatial distribution characteristics of the main pollutants in the irrigation area’s drainage ditches;The water and soil environment was evaluated,and related measures to improve the water and soil environment of the irrigation area were put forward based on the evaluation results and the existing problems in the irrigation area,in order to provide a scientific basis for the green development and modernization of the irrigation area.The main findings of the thesis are as follows:（1）At present,the overall water quality of Guangli irrigation district can meet the water requirements of agricultural functional areas,but the eutrophication level is high,100%of the water body is in eutrophication state,and 44.4%of the water body is in heavy eutrophication state.（2）The spatial and temporal distribution characteristics of main pollutants（TN,TP）in the main canal water of Guangli irrigation area are obvious,mainly nitrogen pollution.The average concentration of TN was 5.80 mg/L,which was 2.9 times of Class V water standard of surface water.The ratio of nitrogen to phosphorus was 43.04:1,which was beneficial to the growth of algae.The concentrations of COD_Cr and BOD₅ were low.During the monitoring period,90.3%of the water bodies were below Class V water standards,and the pollution degree was light.（3）The soil organic matter content in Guangli Irrigation District is relatively good in the soil tillage layer.According to the soil classification standard,it belongs to the secondary or tertiary soil.The soil total nitrogen is also between the secondary and tertiary levels,and the total phosphorus content is in the fourth or fifth stage on average.It is recommended to reduce the application of nitrogen fertilizer and increase the use of phosphorus fertilizer to reduce the non-point source pollution of farmland and improve the soil quality.（4）The sources of pollutants in the drainage ditches of Guangli Irrigation District are complex,including not only farmland drainage,but also domestic sewage and industrial wastewater,and the emission points are complex and diverse.From the perspective of time distribution,affected by rainfall and inflow of supplementary residual water,the drainage of Guangli Irrigation District has obvious seasonal characteristics.From the spatial distribution,the total drainage outlet of the irrigation area（Zhaozhuang）gathers the drainage of the whole irrigation area.Compared with the other two sampling points（Songcun and Shangyuan）,the mass concentrations of TN,TP,and ammonia nitrogen are higher than 56.9%,respectively.65.4%;6.8%,9.5%;86%,126.6%,the pollutant concentration is relatively high.（5）Combined with the actual situation of Guangli irrigation area,23 indicators were selected and the fuzzy analytic hierarchy process was used to evaluate the water and soil environment of the irrigation area.The evaluation believes that the water and soil environment of Guangli Irrigation District is generally"good",but at the same time,water management and water resources protection in the irrigation area are still weak links.It is recommended to focus on strengthening the construction of the water ecological health system in the irrigation area,increasing the irrigation water utilization coefficient and ensuring ecological water demand.Rate,reduce groundwater exploitation and rational use of chemical fertilizers.