Effects Of Land Use On Karst Groundwater Quality And Quantity

In recent years land use change and its impact on the environment has become the forefront and hot spots of global change research, because a land use is the most prominent landscape signs in the Earth's surface system, it can reflect on human activities on the ecological environment.With increasing human activities, the natural karst ecological environment has been devastated, karst groundwater changes are very outstanding problems. Through land use change the human has produced a significant impact on the vulnerable and sensitive karst hydrological systems.Mark Ellaway, and many foreign scholars studied land use impact on karst groundwater quality, but it more concentrated in researches on a single point or block size and certain type of land led to changes in the water quality, and lacked researches on basin or greater regional scale and type of combined land use changes influenced the water quality; for water quantity, there were only confined that a change of forest or grassland on the supply of karst groundwater is increasing or decreasing and the construction of drainage systems and other human activities resulting in less aquifer recharge and water depletion; in the country Yuan Dao-xian Academicians, Jia Ya-nan, Jiang Yong-jun and other researchers , using previous land use maps, information and groundwater monitoring data, for the basin, in terms of time and space on the sequence, analyzed laws that land use effect karst water quality in respective research areas, the results showed the karst groundwater quality and land use changes were consistent in dynamic changes, and land use changed karst groundwater quality in the time and space had either a positive side or a negative side; for the researches of karst groundwater quantity changes, these only had agricultural land use conversion and excessive exploitation of underground water resources caused significant changes of water quantity.This paper on the basis of previous research experiences and achievements, for study in Diaojiang River Basin in Guangxi - the typical karst watershed of the southwest region, combining with doing the preliminary analysis of the situation by the Guangxi Institute of Geological Survey in 2006 for Diaojiang River Basin water quality in the last 20 years and drought and lack of water, using remote sensing and GIS technology, interpreted and analyzed land use circumstances of the study area, and in accordance with surface water quality evaluation of a single factor and karst groundwater quality integrated evaluation, as well as the results of water quantity changes, in Diaojiang River basin from time and space firstly studied effect connection between the land use and karst groundwater quality and quantity, drew the following conclusions:1. The duration of karst groundwater and surface water quality changes in the study area has a very good consistency, the upper reaches of many mining and mineral processing plant influenced the surface water is the main reason for certain high ion concentration of upstream karst groundwater quality, while in the middle and lower reaches the exposed karst water points are mainly influenced by farmland farming and production and life of the nearby residents.2. In the space distribution different concentrations of the same kind of ion by the impact of land use types mainly show: the higher concentration of Ca2+ and HCO3- centralize distribution in the shrub forest, woodland, uncovered rock and gravel, their relatively high concentration of Cl-, SO42-, NO3- focus on farmland planted with broader distribution of peak-cluster valley in the Zhanglao, Xia'ao, Banling and Laren village,Longwei drop-spring locating primary school of Banmo nearby has a higher concentration of Cl-, Jiudu waterworks skylights of underground river near roadside of village has a higher concentrations of SO42-,this accounts for easy to have an impact on water quality using agricultural fertilizers and owning dense population, but how to influence concentrations of Al3 +, F- and other ions in the spatial distribution under the ways of land use, still await further study.3. Analyze relevant information and focus on comparison results of the water flow of the eight karst groundwater points over the same period of 2003 and 2004, it confirms that in the study area the runoff of underground rivers is decreasing, the main reasons: mining changed the original land use and made the vegetation cover decreased, the tailings inflowing underground river system plug pipeline reduced the effective runoff, resulting in decreasing the flow of karst groundwater points, in addition, a large number extraction of groundwater for irrigation and production and daily life is also one of the reasons for reduction of karst groundwater.4. The extent results of studying the same kind of ion concentration influenced by different land type show: the resident points and mining, and other special used lands are greater than farmland, and farmland is greater than woodland on the impact of the ion concentration levels (except for SO42-concentration, its phenomenon not obvious), this explain the frequent activities of human in the Karst region is an important impact on karst groundwater quality changes.5. In the research region choose a small peak-cluster depression (valley)--three sheep region, doing in-depth studies, and further prove three land types of the mining land and the residents of settlements and arable land play a dominant role of influencing karst groundwater quality; urban and rural population and rapid economic development lead to a significant growth in construction sites, in order to meet production and life needs drew massive groundwater, this makes karst groundwater significantly reduced.Summing up the above, this paper found the main types of land use impacting karst groundwater quality and quantity changes in the research area, explained impact of ways and its impact on the extent, this will have an important practical significance for improving the production and life of people in the region on the quality of water and solving local regional droughty problem of water shortage, and will also provide a scientific basis for achieving virtuous cycle of Diaojiang River Basin Karst Ecosystem, resources and the protection of the environment and the sustainable development of the local economy .