Climate Change and its impact on Groundwater Table Fluctuation in Precambrian rocks of Chamarajanagara district, Karnataka, India using Geomatics technique

摘要

Change in climatic conditions directly affects the hydrologic cycle and gradually the groundwater table. Rise in temperature increases the evaporation of surface water and transpiration in wetlands. This results in low precipitation amounts, timings and intensity rates; which impacts on surface water bodies (rivers & lakes) as well as subsurface water bodies (change in volume and distribution of groundwater recharge process) and direct changes in major long-term climate variables such as air temperature, moisture content, precipitation and evapo-transpiration. Geomatics encompasses Survey of India (SoI) Toposheets, Remote Sensing (RS) Satellite Images, Geographic Information Systems (GIS) and Global Positioning Systems (GPS) with limited Ground Truth Check (GTC). Efforts have been made to evaluate the data from 27 representative rain gauge stations and analyzed the season-wise rainfall variation over a period of 26 years (1984-2009). 36 representative well samples are considered to study the groundwater table fluctuation from season to season of about 12 years (1998-2009). The spatial variability of mean annual precipitation depends upon the topographic factors like exposure of station to the prevailing wind, elevation, orientation and slope of the hills/mountains. The average and mean rainfall over the area are calculated using arithmetic mean, thiessen polygon and iso-hyetal methods. Average rainfall is the simple arithmetic mean rainfall measured in the area; while Iso-hyetal method has been adopted for spatial distribution of rainfall with respect to a particular direction. Rain gauge stations are plotted on a base map with their respective amount of rainfall and then the contours of equal rainfall (isohyets) are drawn using Surfer v8.5. The different rainfall intervals obtained (area between the two adjacent lines) are helpful in understanding the variation of rainfall over the study area. The final results highlight the impacts of climatic change over groundwater table fluctuation in typical Precambrian rocks of Chamarajanagara District, Karnataka, which is a suitable model in similar geological conditions.