Groundwater Circulation Of Wulan Basin

Wulan basin is located in the central part of Qinghai Province, the Mongolia TibetanAutonomous Prefecture of Haixi state and the eastern Qaidam Basin. It is a semi-arid are andhas a typical plateau continental climate, scarce rainfall, strong evaporation, temperaturedifference between day and night. The basin surface water spatial distribution is extremelyuneven, and the long freezing period, therefore, fully utilization of surface water to meet thewater requirement of this Basin. On the contrary, the groundwater has the characteristics ofwide distribution, good water quality, water stability, evaporation and less pollution, systemregulation and strong, can meet the large range of daily water demand, the more advantage inthe frozen period. Especially the aquifer thickness is large, the piedmont alluvial plain area issuitable for the use of underground water supply.In this paper, Chinese Geological Survey held a project which is "the exploration"groundwater in key areas of circular economy pilot area of Qaidam Basin. The aim is to studythe regularity of water cycle with the groundwater dynamics theory, through the typicalprofile of water chemistry analysis and numerical simulation of groundwater flow technology,the study area reveals the chemical characteristics of water and groundwater circulationpattern. According to the research, the author draws the following results:1.Through the data of water chemistry analysis, It is supposed to be divided three kindsof the water chemistry type, which are Cl, Cl·SO4and Cl·HCO3·(SO4) In the northwesternbasin where mainly accounted for22.34%Cl·HCO3—Na·Ca water, but Northeast accountedfor25.99%CL·SO4—Na·Mg water, meanwhile in the central and southern mainly about CL—Na type water, which nearly approach51.67%. Mineralization in the Northern Piedmontarea is less than1g/L, which belongs to the fresh water. Piedmont alluvial fan edge watersalinity is1~3g/L, which belongs to the brackish water; basin in central and southernmineralized degree is larger than3g/L, which belongs to the water or strong salt. Salinity andhardness from the north and south sides of the basin to basin center increases ceaselessly.From north and south to the center of the basin, hydrodynamic condition is worse, lacustrinehydrodynamic conditions of groundwater in plain the difference and enrichment in favor of Cl, which has the highest salinity.2.The water, diving and precipitation have close relationship. The rain is the main supplysource of river, on the country the river alluvial fan area is groundwater recharge zone, divingby the river. By calculating the groundwater recharge, the northern red circle basin elevationis about3100m where the supply temperature is7.0℃; blue circle Southern groundwaterrecharge elevation is about3900m where the supply temperature is about4.3℃. The value ofδ D in the northern part of the basin, river water and spring water ranges from-67.05to-56.24(mean-62.40). The value of δ18O are varied from-10.2to-7.97(mean-8.89). Fromthe above results, it shows that there are great hydraulic connections between the3kinds ofwater and the unconfined water cycle condition is better in northern region. The value of δ Dis between-77.48to-74.58(mean-75.72), and the value of δ18O ranges from-10.77to-10.2(mean-10.51) in Basin South. the values are lower than the red circle dive, dive furtherillustrate the supply source of the southern and northern parts of different. Saishenke profile,from the river alluvial river on diving supplies to around40%in the proportion, that is to say,the piedmont alluvial fan area about40%of diving. The main recharge is from the river.3.Wulan basin on the northern and southern water circulation system is divided intothree levels, namely the local circulation system, the intermediate circulation system and theregional circulatory system. The north part of the basin, the permeability coefficient ofaquifer is strong and underground water salinity is less than1g/L, what’s more the waterchemical type is CL·SO4—Na·Mg, at the same time the groundwater velocity exceeds0.4m/d belonging to the strong runoff zone, finally the circulation depth were30-90m. In themiddle cycle system, the changes of groundwater property and coefficient of permeability areversatile, groundwater velocity is0.1-0.4m/d, belongs to the medium flow zone, circulationdepth of50-150m and the renewal cycle ability is poor; the regional circulation system ofdistribution under the local groundwater flow system and middle groundwater system, whichis developed very well. In this area, the groundwater velocity is0.1m/d and its circulationdepth is less than30–400m, of course the update ability is poorer. In the southern part of thebasin, the local circulation system of groundwater salinity is greater than1g/L, water chemical type is mainly CL—Na, groundwater velocity is0.1-0.4m/d, belongs to the mediumrunoff belt and the circulation depth is varied from20-100m. groundwater flow intermediatecirculation system and regional circulatory system groundwater speed is less than0.1m/d,which are belonged to the weak runoff zone.