Approach to Topographic Map, Hydrogeological and Environmental Isotopes Analysis to Delineation of Watersheds in Drought-prone Areas

Gunung Kidul regency is one of the regencies in Indonesia that almost every year (often) is susceptible to drought, there is an even in term of synonymous with a drought in the province. Water is the essential lifeblood on Earth, with the power to generate, sustain, receive, and ultimately to unify life. Water is also one of the most important resources that need to be protected, conserved, and maintained to support humanity and all life on earth. Drought is a state of shortage of water supply in an area in which a prolonged period (several months to years). Usually, these events appear if a region is continuously subjected to rainfall below the average. Dry season long will cause drought. Drought is also a lack of water for human life and other living things in an area that is usually not a lack of water. The environmental isotopes most widely used as a tracer in the study of hydrology cycle are the stable isotopes deuterium (2H), oxygen-18 (18O) and carbon-13 and the radioisotopes tritium (3H) and carbon-14 (14C). The use of environmental isotopes as a tracer in groundwater studies are usually complementary to approach topography, hydro geology, and geology which has been frequently used. The result of this research show that elevation as an orthometric height of the 15 wells water in the research has a variation elevation which spread at most of the district in The from -18.390 m at Girisubo district up to 238.599 at Nglipar district m. Concerning with elevation of the water table at several geological cross section (East - West) are close to orthometric height.