Response Of Karst Hydrology System Under Different Rainfall

Water is main resource for mankind's survival, water resource is the basic guarantee of human living and developing, development and utilization of water resource is the permanent objective of mankind. In China, freshwater resources is lack, the world average per capita water volume accouts for only 1/3. It's very important for human, livestocks, agriculture and industry in dryland arears that exploit groundwater resources in a scientific and appropriate way. Karst water is a significant kind of freshwater resources in China, and it's reserves accounted for groundwater resources is 1/4. It is the main water resources for daily life and production in karst arears. But karst arear is considered to be fragile environment which is the same as the edge of the desert. The rainfall quickly infiltrates into underground and caused that soil resources are not coherent with water resources in space allocation, then given rise to serious soil erosion and soil depletion boil. People in these area always lack of water. One of the major reson for a long period poverty and backwardness in karst mountainous region is drought and lack of water. Because of the low capacity of the karst environment, once destroyed, it is difficult to resume shortly. There are special double hydrogelolgy structure, it may be made of up and down parts. Soil and water are separated, the upper is the soil that is lack of water, the lower is underground rivers. The dissolvability rocks has little ability to made soil. The uneven spatial distribution of karst water and surface water and groundwater are closely linked, which made karst water are vulnerable and easy to be impact by human activities. Development, theremore, utilization of groundwater resources become more difficult.Because of the karst hydrological system have a strong sensitivity to environmental change, the traditional methods of observation does not accurately reflect the karst dynamic system changes of short-time scale. We can obtain a large number of first-hand basic data of karst water dynamics and environment-related, by the field automation equipments on long-term dynamic monitoring of karst groundwater. It's has great significance for discovery karst dynamic system operating rules and developing theory of the karst dynamics.This paper analysis operation rules of karst dynamic system of Qingmuguan underground river under different rainfall by automate monitoring for chemistry and flow. Several representative rain were be selected with different intensity and rainfall to study the dydrological system variation; and analyzed the hydrological process line in rising phase and decay phase flow, then calculated and discussed the storage capacity of karst aquifer medium.By monitoring the conductivity, pH, temperature and NO3-, and other hydrochemical indicators for the export of Jiangjia spring, combining with the data of basin rainfall, study the different response of karst hydrological system to different rainfall conditions. The analysis results shows that:1. Research finds that response to karst hydrochemical indicators is very quickly for rainfall by continuous monitoring underground river more than two years. During the rainfall period, especially a downpour, the water level is fast changed. It indicat that the underground river have large-scale karst channel, and the karst aquifer media is uneven, which verified by tracer experiments.2. Response of karst hydrochemical characteristics is not consistent under different rain conditions(different rainfall or rainfall intensity). In seasonal scale, value of karst hydrochemical indicators is low in the rainy season. Conversely, it is high in the dry season. In short-scale, dilution effect of rainwater is apparent in the course of heavy rain or downpour; The conductivity is rapid rise under short-heavy rain; On rainless state, hydrochemical value is changed with different external environment. The value of hydrochemical is significant changes in Yan kou doline, while Jiangjia spring is not obvious.3. By analysis flow line of the flow growth process, storage capacity of the karst aquifer m×edia and it is 2.2 X 104-2.66×104m3. Using and distributing this water resource is very practical significance for drinking water and agricultural irrigation.4. Through analysis on flow decay curve at Jiangjia spring, we found that flow decayed very fast in stage I under the heavy rain, showing a clear channel characteristic; the flow is not significant change in stage III. So the drainage of karst water can be divided into 3 stages or 3 types:the pipe water, the fissure water and the aperture water. The fissure water and the aperture water are the main groundwater resources, which contend more than 90 percent of the total storge capacity. Unlike the heavy rainfall, flow decay can be considered as two sub-flow dynamics under the weak rainfall. Stage I is not present or not obvious; storage capacity of stage II and stageⅢare equal approximately.5. The study of karst groundwater system must take into account the impact of the various spheres. Karst dynamic system is formation of CO2-H2O-Ca system, we must understand the evolution, mechanism and operation rules in karst aquifers, and solve problem of eco-management and soil conservation. So, we must unified with the atmosphere, hydrosphere, lithosphere,biosphere and human activities, and toexplain the role of hydro-geochemical processes.6.Through analysis on flow decay curve at Jiangjia spring under different rainfall intensities, we found that storage functions concentrated in small fractures and pores in epikarst aquifer medium, and storage of karst aquifer medium are more powerful under the weak rainfall.