Study Of Effects Of Ecological Environment On Regulated Function Of Epikarst Water In Typical Karst Area Of Southwest, China

Karst area in southwest of China is fragile environment. The rainwater fast infiltrates into underground for special geological background. It could lead that soil resources are not coherent with water resources in space distribution. So there are thin soil, seriously water loss and soil erosion and short surface water in these karst areas. Those local people lives much poor. One of the main matters of poverty is shortage of water and dry in karst mountainous district without soil. As a part of efficient exploitation karst water, the Epikarst water has become an important wellspring for those people living in mountainous area. Of course it could also be used to bring the karst stone desertification under control. The water of epikarst aquifer in karst hydrological system could be adjusted by epikarst zone and ecological environment. So the special dual hydrogeology structure was formed for karst aciton. It may be made of up and down parts. The upper is mainly consisting of the epikarst water. The lower is mainly made of underground rivers. Obviously soil and vegetation affect the water cycle of epikarst. There is distinct difference for hydrological course of epikarst spring under different ecological environment through abundant wild research. In desertification area the discharge of Epikarst spring increased and declined rapidly. There was flood in rain season while drought in arid season. But in a dense and primitive forest the discharge of epikarst did not be cut off ever and keep a stable flux. Thus the effects of ecological environment on regulated function of epikarst water should be known and holded throuth a lot of research. Furthermore to master the function and mechanism is great important for preventing and harnessing the desertification. It also includes exploitation epikarst water through ecological recovery. Homochronously it can also be built the base for SVAT(soil-vegetation-atmosphere transfer) model in karst area.The thesis aimed at four epikarst spring watersheds respectively formed under four kinds of different ecological environments in Nanchuan city of Chongqing, China. They are respectively Shuifang spring watershed in Mt.jinfo, Boshuwan spring watershed in Dapuzi village, Lanhuagou spring watershed and Xiangjiayuanzi Spring watershed in Nanping town. The main vegetation is subalpine meadow in Shuifang spring watershed, Pinus massoniana in Boshuwan spring watershed, corn in Lanhuagou spring watershed and camphor in Xiangjiayuanzi spring watershed. In the study, firstly, characters of epikarst aquifer were discovered through the recession curve of epikarst spring. Secondly, regulating function of soil could be known on the basis of the seriate same medium model through monitoring soil water content in rain. Thirdly, the effects of vegetaion-soil on the quality of epikarst water be knowed through the analysis of water quality on rainfall, throughfall, soil water and epikarst spring. In the end effects of ecological environment on regulated function of epikarst water were mastered on the base of the front analysis.Firstly recession process of epikarst spring can be divided into three stages. Recession coefficient of epikarst spring and the ratios of conduit water, fissure water and miscibility gap water in epikarst aquifer could be respectively calculated in the stage I, stage II and Stage III according to the analysis of recession curve of epikarst spring flux. The conclusions were as follows: (1) the amount of fissure in epikarst aquifer could more easily increase under good ecological environment. Recession Velocity of fissure water could become smaller and recession coefficient could become smaller too. (2) The effects of ecological environment on recession coefficient of miscibility gap water in epikarst aquifer were not obviously. The recession coefficient of miscibility gap water was mainly controlled by porosity of carbonates. (3) Heaver litter layer might slow down the recession velocity of conduit water. Its recession coefficient became small and conduit water might be recognized as fissure water in calculation. (4) Regulation function of epikarst was remarkable under good ecological environment. The total ratio of fissure water and miscibility gap water in the whole water in epikarst aquifer, the more important water, were all respectively above 90% in Shuifang spring watershed, Boshuwan spring watershed and Xiangjiayuanzi spring watershed.Secondly the increment of soil water could be calculated on the basis of the seriate same medium model through monitoring soil water content, rain and flux of epikarst spring. The characters of increment of soil water varied with rain could be analyzed. Correlation between the increment of soil water and flux of epikarst spring was gripped too. The conclusions were as follows: (1) soil was obviously of regulating epikarst water. Before it was raining the increment of soil water was negative. When it rained the increment of soil water began to increase. But it could not arrive at the maximum value right now. The maximum value of increment of soil water lagged behind the maximum value of rain. Synchronously it was earlier for the increment of soil water than the increment of epikarst spring flux. Because of regulation of soil the maximum of epikarst spring flux lagged behind the maximum of rain. (2) Storage capacity of soil was focused on the middle-up soil layers, not the whole soil layer. (3) Soil was obviously of regulating function in good ecological environment. According to obtained value the coefficient of soil regulation were respectively 90.74%, 72.65%. 52.13% and 33.33% in Boshuwan spring watershed and Shuifangquan spring and Xiangjiayuanzi spring watershed and Lanhuagou spring watershed.In the end on the basis of analysis of HCO₃^-,Cl^-,Ca²⁺,Mg²⁺,Na⁺,K⁺,SO₄^2- ions concentration in in rainwater, throughfall, soil water and epikarst water, Characters of these varied ions concentration were respectively obtained in four spring watersheds. Furthermore chemical characters of epikarst spring varied with rain could be analyzed. The conclusions were as follows: (1) ecological environment was relatively of regulating pH value of water. Based on the analysis of the pH value of rainwater contrasted with throughfall, vegetation played a role of acidification rainwater, while karst soil was of relieving acid through the pH value of soil water contrasted with throughfall. The pH value of water decreased and became thin acid from rainwater to throughfall. On the contrary the pH value of water increased and became thin alkali from throufall to soil water. (2) vegetation-soil could vary chemical characters of rainfall, accelerate elements to move and add the total amount of chemical materials of epikarst water. Those ions concentration increased from rainfall to epikarst water, especially for HCO₃^-, Ca²⁺ and Mg²⁺ ions. HCO₃^-, Ca²⁺ and Mg²⁺ ions concentration in epikarst water were respectively about 25, 14, 30 times of these ions concentration of rainwater. (3) Agricultural environment could accelerate NO₃^- and SO₄^2- ions in soil to be released. The increase of NO₃^- and SO₄^2- ions concentration were respectively 60.4% and 60.7% through epikarst water contrasted with rainfall in Lanhuagou spring watershed. While they were only 5.5% and 37% in Xiangjiayuanzi spring watershed. (4) Ecological was obviously of regulating function for chemical characters of epikarst water. For epikarst spring the max values of temperature, pH and conductivity all lagged behind the Maximum of rain.In summary ecological environment was obviously of affecting regulated function for epikarst water. It affected not only the amount of epikarst water, but also the quality of epikarst water. Good ecological environment was obviously of regulated function for epikarst water. So forest for water and soil conservation must be protected in Preventing and harnessing the desertification and Exploitation epikarst water through ecological recovery so that ecological environment in mountainous karst area would become more and more well.