Discussion On Simulation And Forecast Of Groundwater And Ecological Effect In The Western Jilin Province, China

This paper is based on two projects. One is about environmental protection and science in Jilin, named'Research on lawn ecosystem environment deterioration mechanism and recovery in western region of Jilin province'. The other is a technology project belongs to national territory resources hall of Jilin, named'Research on groundwater over development and surface ecosystem in western region of Jilin province'. We carry on numerical imitation on groundwater current and analysis the amount of water that ecosystem needs to forecast the groundwater water level in the following 15 years in this area. This paper analyses how the changes of the level of underground water influence the ecosystem surface and do study on the ecosystem effectiveness. Based on the conclusion of this study, we put forward some meaningful suggestions in order to improve water resources and environmental construction in western of Jilin.The western of Jilin mentioned in this paper refers to the area located eastern longitude 121°38'~126°17', northern latitudes 43°53'~46°18', high distance 150-200m. This area is located in a crossing weak ecosystem environment which is half wetness and half drought. It is one of the most alkali lands in our country. It belongs to southwest department of Songnei plain, connects to Heilongjiang in north, Changchun in east, Inner Mongolia in west and southwest, Siping of Jilin in southeast. The area of the whole region is 47011 km2, and the salt alkali area in this region is 15327km2, it means 32.6%. The western plain in Jilin includes tow cities, Baicheng and Songyuan, and the population is 4,755,000. That area is placed in the transition district which is half wetness to half drought, and has the characteristic of the two climate zones. The whole area is mostly influenced by Inner Mongolia inland climatic zone. It carries the characteristic of inland climate, dry and windy in spring, hot and rainy in summer, cool and big temperature gap in autumn, long and cold in winter. Because of the influence of climate, the ecosystem environment of the western region is weak. The surface water resources of this area are in the severity shortage, and there is not enough control system to regulate the passing surface water. As a result, the using of surface water resources is small. So they make use of the underground water to satisfy the water need of industry, agriculture and living. This behavior makes the water that ecosystem environment need occupied, the water need of wetly area and lawn can't be guaranteed, and the area of surface water become small gradually.Based on the analysis of the geology and hrogeology conditions of the research area,this paper constructs a concept model, sovles the conspronding mathematical model using Feflow, and makes a prediction of the groundwater level for the coming 15 years.The result shows both the confined water level and unconfined water level have been decreasing year by year,especialy for the unconfined water level ,which has the deepest drawdown of 5 meters or more .The decrease of confined water level is not obvious and dramatic drawdown of 2 to 4 meters only appears in the areas of poor recharge conditions. In some areas,there exists cone of depression which has the tendency to extend.The nature plant in Jilin western region includes forest steppe, steppe, grass and marsh. The artificial plant includes farmland and shelter forest, etc. This paper categorizes the planting types mentioned above, calculates the amount of water that farmland, grassland, and forest land need. In the calculating process, we use direct method for farmland, water quantity balance equation for grass land, Penman comprehensive method for forest land. Meanwhile, we get the amount of water in shortage for ecosystem according to average water fall in many years. And we use this amount as the amount water that the surface water and underground water need. The surface water resource in this area is in shortage, so the water that ecosystem need is satisfied by underground water in large extent. We analyze the vicious cycle problems which happen in the research area according to the forecast of the underground water level and the amount of water fall in the following 15 years and the cumulative amount of water that ecosystem need in the following 15 years. 1. The underground water level descends year by year cause more difficult for ecosystem water need, which will influence the scale and function of the surface planting ecosystem. 2. The short amount of water for surface planting ecosystem will enlarge the excretion for underground water; turn worse the groundwater water level to descend. At the same time, the area of the surface plants will become small and the functions will descend because of the shortage of need water and other reasons. This will enlarge ground evaporation, cause the amount of water fall descend and drier, make the supplement for underground water become small, which will cause underground water level descended year by year. The final results of this problem are: the gradual descend of underground water level makes water shortage for the surface ecosystem more and more serious. And the deterioration of natural ecosystem happens, such as wet land became small, the area of grass and forest descends and hungriness turns worse. All these problems will influence people's life directly. The weak farmland ecosystem will be threatened by harsh natural environment. The lowness of underground water level will make it more difficult for people's life.We analyze the ecosystem effect caused by the change of the underground water level according to the amount of water that ecosystem needs. Along with the current change of the underground water level and environmental change, there need more economical investment and resources investment for the farm crops. And this behavior will affect the other type plant. People put more water resources on farmland will cause unbalanced expenditure for surface water and underground water, which will influence the healthy development of grassland, forestland, marsh and lake ecosystem. Meanwhile, when the output of the farmland is much lower than the input, people will give up the lower productive farmland and redevelop new land. This will not only cause the original weak farmland hungering, but also threaten other ecosystem environment, causing the environment worsen. The area of the natural plant ecosystem such as lawn, woodland and marsh etc. descends yeas by yeas because of people's behavior. And their original functions, such as self-restraint humidity, keeping the water and soil and regulating the climate, also deteriorate in large extent, and cause drought and hungriness.From all these problems, we can see that it is necessary to focus more on water resource management. And considering that the amount of water that the farmland need is very huge, which is the major reason for the water shortage of the area, so it is very necessary to strength the scientific management for agriculture. In addition, the development of the herding industry will influencer the lawn ecosystem, so adopting the modern principle for herding industry is very crucial. In a word, in order to promote the sustainable and harmonious development for resources, environment and society, we have to change the traditional operating method, put more investment on scientific technology and strength management power of the government.