Geosonar for impermeable layer mapping in urbanized Upper Belik catchment, Yogyakarta

The scarcity of water in most Yogyakarta grounds water basin is because of decreasing the groundwater recharge as the implication of the build-up area growing. One exception is in Upper Belik Watershed in which more than 95 covered as paved area. In order to reduce the runoff, the infiltration well must be applied. The artificial well design depends on the characteristics of impermeable layer that can be seen by its depth. So the analysist of impermeable layer depth is extremely important to be researched. Distribution of the impermeable layer can be interpreted using Geosonar. Therefore, the purpose of this research is to find the distribution of impermeable layers in Upper Belik Catchment. The primary data used systematic random sampling base on grid size 125x125 m. Spatial data analysis of the impermeable layer utilized to visualize the result of material type which consists of sand, little gravel, tuff, clay sands, sandy clay, and gravel in research location. Variation of impermeable layer depth divided into 5 classes which are: I (9-10 m); II (10-20 m); III (20-30 m); IV (30-40 m); and V (>40m). The composition of the impermeable layer material dominated by clay and tuff in Upper Belik watershed and located below the groundwater level.