Yaji Karst Experimental Site


  The karst area of southwest China is about 1 million km2, 90% of which is fengcong (peak cluster depression) landform.It suffers from both drought and flood. Water resources problems are obstacles to local long-term economic development. In 1986, the Institute of Karst Geology (IKG) of Chinese Academy of Geological Sciences, supported by Sino-French scientific and technological cooperation projects, established the Yaji Experimental Site on Karst Hydrogeology. Since then, longtime research on hydrogeology has been carried out. It not only helps to promote karst S&T innovation, but serves as a good platform to cultivate young scientists and raise the public awareness on karst science. The Yaji Experimental Site on Karst Hydrogeology is located at the junction of peak cluster depression and fenglin (peak forest plain), 8 km from IKG with beautiful sceneries and convenient transportation. The carbonate rocks developed in the strata of Rongxian Formation, Devonian System, formed a peak cluster depression hydrological system after longtime geological evolution. The area of peak forest plain is covered by Quaternary strata of 3m, with buried karst aquifer at the bottom. There are abundant karst phenomena, such as karst depressions, sinkholes and blue holes on the surface, and underground conduits and caves. The Yaji Experimental Site, with 2 km2 in area, is composed of 4 integrated karst spring watersheds. With its hydrogeological conditions being clearly identified, it is a good place for field research on karst water.

  The main scientific goal of Yaji Experimental Site is to understand the occurrence and flow of groundwater in karst media, and to establish mathematic models to reflect the structure and flow process of karst drainage systems and to predict the changes in water level and spring discharge. Meanwhile, according to the development of modern karstology, it can also be used to carry out scientific research on carbon cycle, karst ecosystem, soil microbiology and other related fields.

  After 25 years’ development, certain research achievement has been made in the Yaji Experimental Site as follows: Recharge of karst springs and boundaries of watersheds have been identified by tracing tests, and the flow speeds of karst conduit flows have been calculated by the tests results; With the hydrochemical and isotopic rainstorm monitoring at 9 boreholes distributed in both recharge area and discharge area, 8 epikarst springs 4 karst springs, different proportions of two rainfall recharge ways of diffusion and concentrated have been recognized. And a new point of view has been put forth that the participation of soil CO2 in karst processes increases the calcium of karst water after rain rather than decrease; The hydrological observation and measurement of the overland flow observation sites, karst springs and cave dripping water provide different hydrographs as well as 5 flow types in karst area, which reveals the karst slope infiltration and runoff mechanism; The box models, reflecting special physical structure of karst media, have been created. Good simulation results have been made by taking advantage of the hydrograph calibration models of borehole water levels, epikarst springs and karst springs. The assessment on the storage function of epikarst zone in different precipitation conditions has been done with the Yaji models. The significance of epikarst zone to the system has been first recognized. The above scientific study results gained in the Yaji Experimental Site have been given to the world. With 59 published papers, of which 6 are SCI included, and 1 printed monograph, the Yaji Experimental Site has exerted an influence in the academic circle. Except for scientific research, the Yaji Experimental Site has taken its responsibility on karst science popularization. Since its establishment, it has welcome professors and students of both Chinese and foreign universities (such as University of Oxford, Huazhong University of Science and technology, and Guangxi Normal University) for field work and practice. Even every visiting scholar of the Institute of Karst Geology has a visit there.

  25 years’ experience has laid a sound foundation for further development of the Yaji Experimental Site. Under the new circumstances, large-scale karst water project construction to be urgently undertaken and new challenges from climate change to water resources demand further innovation of karst water scientific research. On the other hand, the IGCP 598 “Environmental change and sustainability in karst systems”, which is approved in February, 2011, will be mainly conducted by the Karst Dynamic Laboratory. At the same time, the Yaji Experimental Site will be chosen to be one of the observation sites for international comparison study, which puts forward higher requirements for its facilities and construction. Led by Professor Yuan Daoxian, the study team of the Yaji Experimental Site will continue to move forward.