Study On Water Environment Of Lake In Arid And Semi-arid Areas In Northwest China

Lakes are the principal component of wetlands,it plays a very important role in regional climate regulation and biodiversity preservation.The lake water quantity and water quality of Lakes in arid and semi-arid areas in northwest China,controlled by both natural and human factors,with the rapid development of economy and society,the influence of human factors on water quantity and water quality of lakes in arid and semi-arid areas becomes more and more strong,it seriously affects the function of lakes.Hongjiannao Lake is located in the boundary zone of Shanxi and Inner Mongolia province,it is the largest and youngest desert Lake in China,a Provincial Nature Reserve of relictus,and also an important target for the protection of good lakes in China.With the water resource shortage in Hongjiannao watershed,the lake area shrinks rapidly,lake water quality has changed.How to improve the lake area and protect the water quality,is the main task of Hongjiannao protection.This Research has important value of providing a good environment for relictus migration.This paper uses water balance model,analysis the ways and quantities of Hongjiannao water supply and consumption,find the main ways of water supply and consumption.Use the scenario analysis predicting the area of a lake.Based on the theory of hydrological geochemistry,compared water quality indicators of rivers,lake and Similar lakes,characteristics of water quality change in inland lakes are analyzed.According to the principle of conservation of matter,forecasted the change trend of water quality of Hongjiannao,proposed the countermeasures and measures of Hongjiannao water quality and water quantity protection.The conclusions were summarized in this following:(1)Established Hongjiannao water balance model,the results showed that,Hongjiannao watershed average recharge is 1.321×i08m3/a,interannual variability is large,watershed surface runoff recharge is the most important source of recharge.Basin water average consumption is 1.588×108m3/a,interannual variation is small,the evaporation of water consumption is the main way of water consumption of Hongjiannao watershed.The annual water consumption of Hongjiannao watershed is greater than annual recharge in most years,average annual loss is 0.267×108m3.(2)Set up a variety of scenarios,predicted the area of Hongjiannao,the minimum value is 13.82km2 and the maximum value is 39.16km2,and pointed out that adjusting the operation of upstream reservoir should,increasing the water saving irrigation area is the key factor to maintain the water balance of the basin and restore the surface area of the lake.(3)Compared water quality indicators of rivers and lake,Based on the theory of hydrological geochemistry,the causes of lake water quality indexes are discussed.Proposed that the ammonia nitrogen BOD5 should be determined as a basis for judging the degree of water pollution in lakes.According to the principle of conservation of matter,analysis the water quality of Hongjiannao which under the condition of minimum water quantity,can guarantee above class IV water quality.(4)Based on the recognition of the Hongjiannao environment problems,the protection and treatment measures of water environment were proposed,included that regulation of basin water resources,watershed ecological conservation,watershed pollution prevention and so on.