The Guarantee Of Groundwater On River Ecological Base Flow In Guanzhong Section Of Weihe River Basin

Weihe River is the largest tributary of the Yellow River which is the mother river ofShaanxi Province.lt plays an important role in the socio-economic development. In recentyears, Weihe River base lfow showed a signiifcant downward trend because of the impact ofhuman activities and natural factors. Especially, the river ecological base lfow can not beguaranteed in dry season. However, it is an important part of surface runoff. Its attenuationmeans groundwater weaken the protection of the river. These result decreasing in river runoff,shrinking lakes, drying up rivers and a series of ecological environment negative effects.Therefore，this study carryed on groundwater protection of the river ecosystem base lfow inGuanzhong section of Weihe rive.That plays an important role on theoretical signiifcance andpractical value in maintaining healthy to Weihe River.This stdudy was based on the major projects of the National Science and Technology of“ecological base lfow security technology research in the Weihe River basin Guanzhongsection It is the third topic of" the Weihe River water pollution prevention and control ofspecial technology research and demonstration". This study takes Weihe River ecological baselfow as a main target, guided by system theory. It was starting from the conversion betweenriver water and groundwater. Base on methods of the river base lfow separation, mathematicalstatistics and numerical simulation, the researchcarries out the study of groundwater protectionof the river ecological base lfow and the main results are as follows:(l)By analyzing the concept，characteristics and influencing factors of the river base lfowand ecological base lfow, the study points out that the river base lfow occupies an extremelyimportant position in river ecological base lfow in dry season. In the same time, it indicatesthat increasing the amount of river base lfow in dry season is an important way to safeguardriver ecological base flow. (2)0nthe base of the data collection and ifeld investigation, the transformation diagrambetween river water and groundwater is compiled in Weihe River basin. It shows groundwaterrecharge rivers happenes at more than95%region in Weihe River basin. The region of riverrecharge groundwater is back in the diluvial fan of QinLing mountain and Weinan toTongguan section in Guanzhong segment of Weihe River basin.The rest region is groundwaterrecharge rivers.(3)Throughthe analysis of the BFI (base lfow index), Mann-Kenndal and R/S(RescaledRange Analysis), the research shows that the river base lfow appears fluctuation downwardtrend in Weihe River Guanzhong section in recent60years. Since the1990s，the stream lfowand the river base lfow have been keeping downward trend obviously. The river base lfowaccounts for more than85%of the river runoff in dry season.(4)Inwet year and median water year, the river ecological base lfow can be guaranteedbasically in Guanzhong segment of Weihe River basin. In dry year and particular dry year, theriver ecological base lfow appeares different degree of loss，that is the Linjia village section>Weijia fort section〉Xianyang section>Huaxian county section. In the period of the riverecological base lfow losses，the river base lfow accounts for more than90%of the river runoffamount. As a result, groundwater plays an important role in the river ecological base flow.(5)Inwet year and average year, the groundwater can meet the river ecological base lfowin Guanzhong section of Weihe river basin. In dry season of dry year, the contribution value ofthe groundwater to the river ecological base lfow is between0.6and0.8in Weijia andxianyang station. However, Huaxian station groundwater can satisyf the river ecological baselfow during this period.(6)Inorder to strengthen the groundwater protection degree of the river ecological baselfow，the study puts forward the reasonable exploitation of groundwater and rain lfood ofunderground sotrage system technology.①Aiming at protect the river ecological base lfow in Weihe River Guanzhong section,and taking regional ecological environment development as constraint conditions, the researchstructure the regional hydrogeology conceptual model and groundwater lfow numericalmodel.lt calculates that groundwater development threshold in Linjia village-Weijia fortsection, Weijia fort-Xianyang section, Xianyang-Huaxian county section, is respectively1.78xl08m3/a,7.43><10sm3/a，13.01xl08m3/a.②According to the conditions of geology, hydrological geology and meteorologyhydrology in study area, the reseach puts forward groundwater storage mode: before theQinling mountain diluvial fan, the mountain valley, alongside the river water source and urban rain lfood storage pattern. Under these regulation mode，groundwater can increase the storagecapacity by2.7X108m3/a.③Under the combination effect of area groundwater rational exploitation and a variety ofwater stored underground, the level of groundwater protection to the river ecological base lfowis66%.The research has important theoretical signiifcance and practical use value for theguidance to the Weihe River ecological base lfow protection and rational development ofwater resources. Further more it provides a demonstrate in river ecological base lfowprotection of the northwest arid and semi-arid regions，where the river is severely polluted andwater resource is poor.