Within the framework of environmental quality and dry-land productivity improvement programme, we have conducted a study on the groundwater potential in some selected pilot areas of Wonosari and Wonogiri-Central Java. Detail geological mapping has been conducted to indentify the possibility of finding aquifer potential in the Wonosari Formation. Four limestone facies can be distinguished in the Wonosari carbonate reef deposit, i.e., lower reef slope, upper reef slope, coral reef and algal limestone facies. A non-carbonate layer was also found in the middle part of the Wonosari Formation, which is informally termed as the Sandstone Unit. This study concludes that three groundwater reservoirs can be suggested, namely:
boundary zone between Nglanggran Formation and Wonosari Formation,
sandstone unit, and
the lower slope facies ofWonosari reef.
The Wonosari - Wonogiri area informally named as "thousands mountains" to represent the morphology of the area (karstic morphology). This area is one of the arid area in the Java Island with very short rainy season (3 – 4 months). The soluble limestone which is the main geological formation of the area is leached by rain water during rainy season producing cave and small hills (thousand of hills). There is no surface water body (stream) found in the area. The percolating rain water and seepage water in some part of the area joint to form underground stream. Detail Geological map was constructed based on interpretation of black and white SPOT image data of 1: 100.000 scale and aerial foto data. Special attention was made on interpreting the lithology of the area in case of rock potentially behaving as groundwater reservoir.
SPOT image interpretation was made based on black and white data recorded in 1988.