| Due to the global change and extreme weather events frequent, drought disasters continued in southwest of our country in recent years, more human and animal are short of drinking water. In karst rock mountainous area, due to its special hydrogeological structure, as well as the lack of good vegetation, the drought is particularly serious. Strengthen the understanding of karst mountainous hydrology and water chemistry process, knowing the regulate mechanism in vadose of karst mountainous area, exploring the development, utilization and protection mode of water resources in karst rock mountainous area in accord with, and improving the ability of dealing with extreme drought climate events, are urgent need to be solved scientific problems.In the early1990s, the study of water system and hydrology model in bare karst peak mountains area had been carried out in Yaji Guilin. karst mountain hydrological system was divided into three storage zones:epikarst zone, the lower vadose zone, runoff zone. In the three zones, protecting water resources of upper vadose zone is the key to solve the problem of drought in karst mountainous area. This article choose vadose cave named Xiaoyan cave in Yaji as the carriert to research the underground hydrology characteristic of upper vadose zone in karst mountainous, through regular sampling and on-line monitoring to understand the dynamic variation characters of hydrology and water chemistry in the cave, discussing hydrology process and regulation mechanism of vadose zone on the cave. Final according to the upper vadose hydrology characteristic, put forward methods to exploit and protect the water resources in karst mountain area.Research mainly consists of three parts:the dynamics characteristics of water chemistry and hydrological process; the dynamic changes of the water process and pondage mechanism; The utilization and protection of water resources in karst stone mountain.1. Water chemistry dynamics process(1) The ion concentration of drip water has an obvious relationship with temperature and precipitation, high temperature and rainy weather will speed up karstification, making Ca2+, Mg2+content increased, and heavy rains will bring about a great fluctuation in the concentration.(2) Chemical properties are affected by soil, rock roof thickness and drip water yield. The thicker the soil layer is, the higher is the calcium ions content in the water.(3) Online monitoring showed that the corresponding relation between rainfall and conductivity temperature quantity of drip water was good. They ware rapid responses to rainfall, but the degree of response had seasonal difference, the response in obvious in the earlier stage of rainy season. At the same time, due to piston effect and the regulation of the vadose zone, conductivity peak was slightly earlier than flow peak, but temperature peak relative later than flow peak.2. The cave hydrological processes and flow characteristicsResearching the hydrological and flow, analyzing the hydrological process of rainfall recharge to cave dripping water, including recharge, runoff and discharge. It was found that the hydrology process of XiaoYan cave slop had its own characteristics:(1) Recharge form of the cave include rapid flow and slow flow, the overland flow along the pipeline and fracture directly into cave to form rapid flow, if infiltration water along the dissolve tiny gap into cave was formed slow flow. Two recharge forms will be enhanced when heavy rainfall, but the rapid recharge will soon disappear after the rain, and slow recharge can last a long time.(2) Because of the existence of epikarst, runoff model is distinctive in karst mountainous area, according to the principle of interface runoff, the runoff of vadose zone upper Xiaoyan cave include:slope flow, epikarst flow, pipe flow, also exist interflow in where soil layer is thicker, overland flow is often a mixture of runoff generation from excess rain, soil water and DSRF. Below the epikarst, there is often seepage flow and leakage flow.(3) The discharge form in the cave is various:like dropwise discharge, linear and screen discharge. The speed of discharge also is different, the various forms and the speed of discharge are mainly decided by the recharge and the form of runoff upper the cave.(4) The flow attenuation process has two obviouse dynamics, and attenuation coefficients of the two dynamics are much difference. The attenuation coefficient of first dynamic is much biger than the second one. It shows that there are two obvious uneven aqueous mediums.(5) Analysis of flow attenuation process and separate base flow in cave, we found that the regulation and storage capacity of vadose upper Xiaoyan cave was poor. Base flow only account for11.2%of the total flow, drought and flood easily happen in such karst mountainous area with such storage characteristics.3. utilization and protection of cave water resourceThrough analysis of water chemistry and flow process, we know that hydrological process model in Xiaoyan cave. Based on the model, we put out many ways to collect water resources in the rainy season, such as building diversion channel to collect overland flow on the slop, building reservoir in cave. Restore the ecological environment to enhance the storage capacity of epikarst, so the time of water attenuation is prolonged, base flow ratio increase. At the end, Less frequent droughtand flood. |
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