Research On Groundwater Regime In The Western Jilin Province

Water is an important natural resource for human survival anddevelopment, and also is a restricted factor of entironment. As the rapiddevelopment of economy, the contradiction of supply and need of waterresources is prominent increasingly. Solving water resources crisis has beenone of the worldwide strategic problems. West Jilin Province lies in thetransition zone between humid east monsoon region and arid inland, andbelongs to semi-arid and semi-humid continental monsoon climate zone.Water resources in the area is relative indigent, water quality in some placeshas been polluted, and problems induced by it are prominent, such as soilsalinization, desertification, grassland degeneration, water loss and soil erosionetc. Therefore, researching regional groundwater regime (including water leveland quality), and determining rational exploitation and treatment scenario areof great significance to ecological construction and economic development ofthe area.This paper simulated the water level depth of typical observation wells inWest Jilin Province with time-series model, analyzed its variation regularity,and predicted the future water level depth. The analyzing results showed thatthe water level before 1995 changed very gently, in a situation of balancebetween exploitation and supply, but after 1995, the water level declinescontinuously, especially in recently several years, the descending amplitude islarger. It will keep declining if without control. The groundwater regime inthis area has two major periods, one is one year, which reflects the seasonalvariation of precipitation in a year, and the other is 7 to 9 years, which reflectsthe annual periodical variation of climate (mainly is precipitation) in the area.The time-series model can't reflect the dynamic mechanism ofgroundwater flow system, which limits its application, so this paper simulatedand analyzed regularity of the groundwater flow combining numerical methodwith stochastic model, which exerts the advantages of two methods. VisualMODFLOW was used to solve the numerical model. Two groundwaterexploitation scenarios were designed, and the future groundwater flow fieldwas forecasted. If exploring groundwater according to the second scenario, theflow fields in future 16 years will not have obvious change, and theexploitation nearly equals to replenishment, therefore, we can exploit thegroundwater according to this scenario. The allowable exploitation amount ofgroundwater in the research area is 2166 million m3 per year.According to a mass of hydrochemical monitoring data, the groundwatertypes of West Jilin Pronvince were ploted out. Although Shukaliefuclassification is simple and pellucid, it has artificial and can't reflect thevariation of water quality in detail. Piper trilinear diagram wasn't influnced byhumen, and can reflect the ecumenic chemistry character of water. So thechemical types of groundwater were classified by combining the two methods.Meanwile, the zoning map of groundwater types in West Jilin Province wasploted by GIS, Surfer, CAD and so on. The analyzing results showed that thehydrochemical composition of groundwater in the research area is verycomplicated. But the anion component in phreatic and confined water mainlyis HCO3-, water of SO42-and Cl-type only distribute locally. As to the cationcomponent, Ca2+ is predominant in phreatic water, Na+ and Mg2+ is secondly,but in confined water, Na+ is predominant, Ca2+ and Mg2+ is secondly.A mass of hydrochemical monitoring data in 1993 and 2004 wereanalyzed and compared, the variation trend of character composition, such asFe, NH4+, TDS, F-, NO3-, NO2-and so on, were researched. The results showthat the distribution trend of every ion in phreatic and confined water isbasically uniform. From hills in the west and high plain in the east to low plainin the middle, the concentration of each characteristic ion increases gradually,especially in middle low-level wetland, all kinds of ions accumulate, TDS isquite high. From 1993 to 2004, the concentration of most ions in the area has arising trend.Once groundwater was polluted due to the reasonless developmemt andutilization, it will infect the entirenment seriously, and will badly endanger thehealth and activity of pepole. So the compositive evaluation of groundwaterquality is an important work to the development and utilization of groundwaterresources. The groundwater quality in West Jilin Province in 1993 and 2004was evaluated with Nemerow index method and synthetical judgement offuzzy mathematics in this paper. As the Nemerow index method haslimitations that extrude the maximal pollution factor excessively and ignorethe weight factor, so it was improved. The maximal score was insteaded by theaverage of the score of pollution factor with the maximal weight and themaximal score, and the weight of every factor was detemined usinginformation entropy, which resolved the two problems. Water quality subareawas partitioned with GIS, the results shows that phreatic water quality in thearea is mainly of â…£ class, regions with good water quality mostly lie inpiedmont hills-pluvial plain and high plain in southeast, water quality in whichis below â…¢ class in general. Water quality in confined water is generally betterthan in phreatic water, mostly of â…¡ and â…¢ class, only in local area is of â…£class. Water quality in 2004 is worse than in 1993, not only phreatic water, butalso confined water has a trend of being polluted step by step. This is mainlyaffected by human activities, and related department should pay great attentionto it. The ions for determining water quality class in the area mainly are NH4+and F-, which are overproof seriously in many areas,so the pollution reasonswere analyzed, and the prevent and treatment measures were taken.The research showed that groundwater environment in West Jilin is stilldeteriorated gradually. If this continues for a long time, it will bring disastrousaftermath to natural ecology and human life, and strengthening the restorationand treatment is imperative under the situation.