| At present, although there are many studies on the water resources evaluation ofGolmud, it may be relatively weak in combining the surface water and groundwater as asystem, and on the formation of whole organization from the source to the end of waterresource still are unavailable. This research based on the theory of groundwater system, putforward the relationship between river and groundwater evolution as the main idea, and alsomade sure the typical section to be the start point to water cycle; meanwhile, field test, waterchemistry, environmental isotope and groundwater flow numerical simulation etc. methodswere used to analyze the formation, runoff and consumption in qualitative and quantitativeways of water resource in Golmud River Basin. From what, the geochemical evolution couldbe revealed comprehensively. Furthermore, water cycle model could be put forward insystematic, quantitative and scientific way. Followings are the findings of this research:(1) With the geomorphic units transforming from high mountain zone to fine soil plainzone, the TDS presents increasing tendency, that is: the value is372.98mg/l,440.75mg/l,572.54mg/l and1,663.92mg/l in high mountain zone, alluvial-pluvial fane zone, overflowzone and fine soil plain zone, respectively. The transform of geochemistry type in GolmudRive is as follow: HCO3-Caâ†'HCO3-Ca-Mgâ†'HCO3-Cl-Na-Ca-Mgâ†'Cl-SO4-Na-Mgâ†'Cl-Na-Mgâ†'Cl-Na. The dominate process is rock weathering in the water in high mountainzone and alluvial-pluvial fan zone. The process is either rock weathering or ions exchange inoverflow zone. It is evaporation in fine soil plain zone. The effect factors mainly are:hydrogeological conditions, rock weathering, evaporation, soil precipitation, ion exchangeand wind influence.(2) The distribution of phreatic are from alluvial-pluvial fan to fine soil zone. Becauseof different hydrogeological conditions, there are different characteristics of the phreatic. Theincreasing tendency of TDS is the same as it is in river water with the transformation ofgeomorphic units. Water types in alluvial-pluvial fan zone, overflow zone and fine soil plainzone are HCO3-Cl-Na-Mg, Cl-Na (it is Cl-SO4-Na in some areas) and HCO3-Cl-Na, respectively. In Alluvial-pluvial fan zone, the SI of magnesite, dolomite, calcite and gypsumare all not saturated, and there is a good hydrodynamic condition with slightly mineralizationin this area. In overflow zone, the SI of magnesite, dolomite and calcite are saturated, butgypsum is still not saturated. The dominate process is not only ions exchange but alsoevaporation for the phreatic directly exposes into the atmosphere with a strong evaporationcondition. In fine soil plain zone, because of the decline of the water table comparing withoverflow zone, the evaporation could be relieved. Nevertheless, the depth of phreatic watertable is still less than the limit evaporation depth, so the influence of evaporation wouldremain. In this area, there is a bad hydrodynamic condition with heavy mineralization andsalinizaiton. In total, the process of phreatic are mainly the weathering of carbonate andsilicate，and from overflow zone to fine soil plain zone, the evaporation gradually occurespecially in overflow zone. The geochemistry type of artesian water is simple and unitary,mainly in HCO3-Cl-Na-Mg(Ca) type. Magnesite, dolomite, calcite and gypsum are allunsaturated. The process of water is water-rock reaction with lower TDS and good waterquality.(3) From the geochemistry, it can be concluded that the high mountain zone is theformation area of water resource, alluvial-pluvial fan zone is the recharge and runoff area,and from overflow zone to fine soil plain zone is the discharge areas of Golmud River basin.The hydraulic connection between river and phreatic is closely, but it is weak betweenartesian and phreatic or river. Besides, from the sources of analysis on major ions, itconcludes that the major source of Na+is come from the dissolution of evaporites (halite andmirabilite) andthe weathering of silicate (albite feldspar); Ca2+andMg2+mainly come fromthe weathering of carbonates (calcite, dolomite and magnesite), silicate (anorthite) andevaporite (gypsum); the dominate source of HCO3-mainly comes from the weathering ofcarbonates (calcite, dolomite and magnesite); SO42-is from the dissolution of evaporite(gypsum); Cl-mainly comes from the dissolution of evaporite (halite).(4) The study on environmental isotope indicates that there are about60%river waterinfiltrate to groundwater in alluvial-pluvial fan zone, and about35%river water evaporate into the atmosphere. Thus, the phreatic in alluvial-pluvial fan zone are mainly come fromrive leakage with the age less than30years and a strong update of6%. The artesian over100m are mainly come from alluvial-pluvial fan zone; the artesian with the depth of200~400m mainly comes from the areas near Nachitai with the age around20,000year andthe update of0.3~6%; and the artesian below400m are from the area with the altitude morethan Nachitai whose age is around40,000year with a weak update of0.3%.(5) Based on the section2-dimensional numerical model, the groundwater flow couldbe divided into3parts: shallow circulation zone, central circulation zone and deepcirculation zone. Shallow circulation zone includes two local groundwater systems, one islocated in the alluvial-pluvial zone with the fast runoff speed (>1m/d) and another is locatedin the fine soil plain zone with the slow runoff speed (<0.05m/d). The runoff speed of centraland deep circulation zones are0.05~1m/d and <0.05m/d, respectively. The water resourceproportions of the three zones are55%,29%and16%in shallow, central and deepcirculation zone, respectively. According to water head and runoff speed, combing withgeochemistry characteristics and environmental isotope calculates, it could be determinedthat the high mountain zone is the formation area of water resource, alluvial-pluvial fan zoneis the recharge and runoff areas, and from overflow zone to fine soil plain zone is thedischarge areas of Golmud River basin. Taking water quality, quantity and renewal abilityinto consideration, water resources should be priority exploitated in strong runoff zone (thatis in alluvial-pluvial fan zone); water resources in medium runoff zone (shallow artesian infine soil plain zone) should be exploitated in a moderate way, and which in weak runoff zone(deep artesian in fine soil plain zone) should be take good care of. All of the water resourcesshould be exploitated in a reasonable way. |
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