Study On The Groundwater And Environment Influenced By Water Diversion Irrigation In Weak Eco-environmental Area Of Zhenlai County

The thesis is based on the topic of "groundwater resources evaluation" of the Water Diversion Project from Nenjiang River to Baicheng City.Zhenlai County is located in western Jilin Province, where the ecological environment is fragile. The main environmental problems of the area are salinization, desertification, and poor quality of original water. For developing the agricultural economy, the local government planned to build up Wujiazi Irrigation area, expand the Baishatan Irrigation area, and improve the paddy with diversion from Nenjiang River. Since the depth of groundwater level is shallow, and the salinity is high with large quantity of fluoride in the soil, irrigation water will cause changes of groundwater concentration of salinity and fluoride ion, resulting in impact on the environment.This thesis mainly introduces the natural economic conditions, the geological and hydrogeological conditions of the low plain in Zhenlai County. According to environmental problems of the irrigation area caused by the water diversion project, the influencing analyzes are made in four aspects, which are water quantity, water level, water quality and soil environment, and in this area both the hydrogeological conceptual model and the simulation model for the heterogeneous isotropy groundwater flow and groundwater quality are studied.In water quantity aspect, considering the complex effects of different recharge and discharge, the storage of groundwater is calculated in current year and forecasted after the project is built. In water level and water quality forecasting aspect, the software of GMS is used to simulate, the water level and the concentration of different ions are forecasted, and the forecasting period is 5and10 years, this part being the main body of this thesis. Finally, according to the results of groundwater level and quality simulate, analyze the trend of groundwater and environment in the Zhenlai area in 5~10 years . The MAP module and MODFLOW module in GMS(GroundwaterModeling System)software are used to simulate the Quaternary unconfined aquifer and confined aquifer of the Zhenlai County, and after the identification and verification of the model, the parameters which can reflect the actual hydrogeological conditions can be got. Based on these parameters, the most suitable irrigation system for the growth of the crops is chosen, and under different climate conditions, the model is used to forecast the changing trend of groundwater level of Zhenlai County after 5and10 years, meanwhile base on model of groundwater flow, and the groundwater quality is also forecasted. Base on the results of groundwater level and quality, conclude the influences on the environment by the projects.The research results show that: (1) the built of Irrigation Area solve the serious problem of water shortage, and increase the storage of groundwater; (2) if the irrigation conditions are constant, under influence of different climate conditions, the rise of water level in this area may be different; (3) though the water level in the area may rise, violent lixiviation action decreases the salinization; (4) the water diversion project makes advantaged influence on groundwater quality. (5) Irrigation has great significance for the protection of existing wetlands, curbing desertification, salinization and the phenomena of grassland degradation.Finally, according to the adverse influences on the environment, we propose some schemes and corresponding management measures for the ecological environment in long run. For curbing salinization, the exploitation of groundwater should be increased while irrigation, which could control the increasing of the water level and prevent the secondary salinization; meanwhile irrigation and drainage system should be strengthened in order to irrigate and drain freely, changing the water timely, which could wash salt. For curbing desertification, more trees and grass should be planted, biological sand-fixation, imply the responsible contract system of grassland, restrict grazing and restore natural vegetation, by doing all that the desertification will be improved.