The Impacts Of Paddy Fields Exploitation On Surface Water Quality And Soil Environment Of Songyuan Irrigation District In The West Jilin Province

This paper presents nature, geological and hydrological conditions of songyuan area, with taking songyuan irrigation area as rearch obsject. Based on the possible environmental problems arising from water diversion project , The paper performed impact analysis mainly from water resources, surface water and soil environmental dimensions, focusing on analysis of the impact on surface water for salt water.It also carryed on a detailed description of soil salinization,desertification and other issues, and proposed method of prevention and control.The water quality monitoring results showed that: chaganlake has the trait of pH value between 8.52 - 8.60,weakly-alkaline,high salinity,soda saline-alkali water and the water pollution is serious with the class V standards .The quality of the second songhuajiang water quality is better, and all indexes except COD can meet the class III standards of"environmental quality standards for surface water"(GB3838 - 2002).According to the the experimental field test results of desalination growing rice for many years in daan and qianguo irrigation district, combined with the degree of land salinization, we identify that the desalination rate is 25% in the first year, then year after year are 20%. Based on the soil salinity and irrigation return water quantity of every district, we determine the water quality of every district year after year, the results show that early development in paddy fields, return return flow have a higher soil salt concentration in water. It will bring a more serious impact on water quality of chaganlake when irrigation return flow was discharged directly into chaganLake. take Na+ and total salt as an exmple, for example, the concentration status of Chagan Lake increased 64.61mg / L and 161.01 mg / L. So choose the right drainage receiver and restore reed wetlands at the same time, to prevent salt water discharging directly into chaganlake.It is particularly important to protect water quality of chaganlake and protect the function of the ecological environment .It is also the problem To be solved of land exploitation in songyuan irrigation district.After the implementation of songyuan irrigation planning, water discharged into the second Songhuajiang was 77.24 million m3/a, row of 9.21 million less than the status m3/a. Because the water into the second Songhuajiang irrigation water quality is relatively better, SO42-, CL-, NO3-, Na + four indicators meet drinking water sources and health standards, through the forecast results of impact on the Second Songhuajiang, both indicators will not bring significant impact on water quality of the second Songhuajiang,and the existing function of the second Songhuajiang will not changed. .During the project planning stage,we select 14 marshes and wetlands as drainage receiver of irrigation return flow. Return water contains eluting salt, will be gradually brought to drainage receiver. During the initial stage of lands exploitation, the salt in the marshes and wetlands will accumulate because the absorption capacity of natural recovery or artificial reed wetlands is less than the amount of salt from irrigation return flow. The amount of salt from irrigation return flow reduce each year. When the amount of salt from irrigation return flow is less than the purification capacity of wetlands, the accumulated salt in the drainage receiver will decrease. As part of the bubble discharge capacity commitments marsh inadequate exploitation in the rice fields, ranging from 0.1-3.4 years, there will be some of the excess return of the water discharged to search outside the dry lake. When beginning to return drainage from the extra year, due to accumulation of bubbles in the bearing vent area within the salt marsh stripping, which then discharged through the foam and then return to the water marsh salt concentration but will return higher than the vertical paddy water, This suggested that can meet the emission standards of Irrigation water does not soak through the bearing vent directly into Chagan marsh and lake.Irrigation and drainage of songyuan irrigation district eased off owed to its reasonable designing according to study on soil environmental impact. Based on the analysis of characteristics of the soil salinity, with a systematic analysis of the specific environment, we preliminary view that the nine paddy fields were washed with a more appropriate and exclusive salt conditions and the reasonable use of the geographical conditions can avoid obvious invasion to adjacent dry land.If managed the operation properly in order to wash and discharge salt on the rails, the risk of secondary salinization is little.Through the joint scheduling of water source (Hadashan water control projects) and the reservoir , using the second songhuajiang water reasonable and 90% of the guaranteed rate that there's no water scarcity in paddy field. Vast areas of land abandonment and abandonment phenomenon will happen.So as long as the water source be guarantied, it have a lower potential risk of desertification owing to irrigation exploitation .Rational use of land resources , protect vegetation, ensuring irrigation water , improving water use efficiency and strengthen scientific management are the effective measures to fight against desertification .The key of saline-alkali lands exploitation in jinlin is the Solution of environment problems on saline-alkali lands exploitation.Based on research results,the thesis provide the necessary countermeasure and suggestion of environmental protection from the environmental perspective. It can provide scientific basis for environmental protection of saline-alkali lands exploitation of jilin province and can guarante the general planning of billion tons of grain production to implement smoothly.