The Dynamic Changes Of Zabuye Salt Lake On The Tibet Plateau

There are more than 1000 saline lakes in China. The studies on the dynamic changes of meteorology, hydrology and hydrochemistry of a saline lake have important value to the resource exploitation and environmental protection. In this paper, we summarized systemically the regular pattern of the meteorological, hydrological and hydrochemical changes of Zabuye Salt Lake, in which lake we have taken field observation more than ten years. the main study of this dissertation concentrated on the following aspect:①the climatic characteristics of the saline lakes on the Tibetan plateau, especially the dependence relation among evaporation rate and other meteorological elements;②Lake level fluctuation and its time-series forecasting, the calculation method of evaporation rate of lake brine, lake water balance, and shoreline recession related to precipitation during the past 30ka;③characteristics of hydrochemical changes, Apply Pitzer Model in simulation of Evaporation crystallization process of winter and summer lake brines, as well as the relationship between brine origin and different kinds of feeding water.Observation data indicating that, the climate in the area of Zabuye Salt Lake showes typical characteristis of low air temperature, few precipitation, plenty of sunshine and heavy evaporation, windy and very dry.In the past 14 years, air temperature was fluctuating with slight climb trend, precipitation increase slightly,too. Evaporation rate showes strong positive correlation with temperature, and certain degree relationship with sunshine, cloudiness and precipitation. the evaporation rate can be expressed as: Em = 10.4122×Tm + 183.2071 or Em=11.0802×Tm-0.8138×Pm+0.2274×Sm+3.2079×Cm+124.3044In which, Em -monthly evaporation , Tm - monthly average air temperature , Pm - monthly precipitation, Sm - monthly hours of sunshine , Cm -monthly average cloudiness.Hydrologic observation indicating that, the seasonal fluctuation of the water level of Zabuye salt lake was affected by snowmelt, precipitation supply and evaporation, and shows a intricate fluctuation.The lake level drop down year by year generally, but heavy precipitation in individual year could lead to high water level lastly. In the past 14 years, the Southen Lake drop down 17cm, while the Northen Lake which is separated with the Southern Lake arise 26cm.The quantitative prediction of lake level have practical value. In this Dissertation, time series analysis, including decomposition of time series model, Winter linear and seasonal exponential smoothing model(Certainty time series analysis method ), as well as ARIMA product seasonal model (random sequence analytical method), were applied, and show good effects at mid--short term.Evaporation is the only way of water drainage for intraflow lakes. Here we improved the Penman formulae as: (/)()E b = ? +γ? / awRLL+?+γγ/awes?edawfuThe formulae introduce the parameter of solution activity, all other parameters are the same as in Penman formulae for fresh water calculation. the improved formulae is more suitable for the calculation of salt lake evaporation, water balance and solar pond evaporation. There are multiple level old shoreline in Zabuye salt lake.The paleo - precipitation corresponding to the multi-level old shoreline are quantitatively estimated using Kutzbach hydroenergy equation, with improved formulae for the calculation of land and lake surface evaporation.The salinity of Zabuye salt lake brine,which is high in summer and low in winter, varies greatly in a year, caused mainly by the crystalization and dissolveing of Glauber.The ion content of SO4, B2O3 , Na, CO3 + HCO3 in lake brine is positive correlated to air temperature,which is high in summer and low in winter.The ion content of Li, K, C1 in brine is negative correlation negative correlated to temperature, that low in summer and high in winter .。Lithium content in intercrystalline brine shows a more obvious seasonal fluctuation than lake brine, meanwhile SO4 in lake brine varied more greatly than intercrystalline brine.Pitzer Model was applied to simulate the crystallization process during brine evaporation at 2℃,25℃and 50℃for summer lake brine and winter lake brine respectively.Result of simulation shows that, mirabilite - natron - sylvite combination appeares during evaporation at low temperature (2℃), whereas glaserite - trona - gauslinite combination appeares during evaporation at normal temperature ( 25℃) and high temperature ( 50℃) . borax crystalized first at low temperature, whereas lithium carbonate crystalized first and borax crystalized at last at high temperature.More natron (2℃)or trona (25-50℃)( only next to sylvite )and few mirabilite (2℃)or glaserite (25℃-50℃)appeared for winter brine evaporation, whereas much of mirabilite(2℃), glaserite (25-50℃)and little of natron(2℃)or trona (25-50)appeared for summer brine evaporation.The main water supply of Zabuye Lake is precipitation, springwater and stream. The simulation of the evaporation of these water shows that although the Initial componant is different, but their hydrochemistry constitution approach to Zabuye Winter Brine when evaporate at 2℃, whereas their hydrochemistry constitution approach to Zabuye summer Brine when evaporate at 15℃and 25℃, indicating that Zabuye lake Brine could be developed from these water source, and precipitation is the ultimate source.