Influences of Land Use/Land Cover on Hydrogeochemical Indexes of Karst Groundwater in the Dagouhe Basin, Southwest China

It is essential to understand how karst groundwater hydrogeochemistry responds to watershed land use and land cover changes. However, little information is available on this response in the karst region of southwest China. Water temperature, pH, electrical conductivity, total organic carbon (TOC), ions concentration, CO2 pressure (pCO(2)), calcite saturation index (SIC), stable carbon isotopic compositions of dissolved inorganic carbon (delta(CDIC)-C-13), and carbon sink ability were monitored during the hydrological year of May 2010 to April 2011 in the eastern and western areas of Dagouhe Basin. The two areas share the same climatic condition but show different land use/land cover. Field data were used to calculate pCO(2), SIC, and karst carbon sink density. The results showed higher ion concentrations, TOC, carbon sink ability, pCO(2) and lower pH, SIC, delta C-13 in the groundwater of the eastern area than those in the western area. In the eastern area, there is larger forest and farmland coverage, both produced and kept more biological carbon sources and lower delta C-13 in the soil-vadose zone. While in the western area, there is larger rocky land and wasteland coverage. All results suggested that land use and land cover pattern played very important roles in this basin. Therefore, the hydrogeochemical indexes selected could be good indicators for the land use/cover change in the studied basin.