Study of Hydrogeomorphological Springs in Tlegung Watershed, Kulonprogo Regency

Abstract

The spring characteristics such as spring discharge, temperature, EC, TDS, pH, spring stream character, and spring emergence type can be linked to geomorphology. This link is the main study in this research. This research was conducted in Tlegung Watershed, which is mostly located in Samigaluh and Kalibawang District, Kulonprogo Regency. The purposes of this study are to determine the springs distribution pattern and the springs hydrogeomorphology characteristics, also to analyze the hydrogeomorphological factors which control the springs’ emergence and characteristics. Data collection method which used in this research is survey method to determine the source of spring emergence, measure spring discharge, test springs’ physical and chemical quality, and validate geomorphological interpretation. The other method which used is collecting secondary data from institution such as RBI maps, geological maps, satellite imagery, etc. The result showed that all springs in Tlegung Watershed classified as perennial springs and gravitational springs with depression, contact, and fracture springs type. Springs discharge in the Tlegung Watershed are classified in Q3 class (10-100 liters/sec) to Q5 class (<1 liter/sec). Electric Conductivity (EC) of all springs are classified in the EC1 (fresh water) with an average of 229,24 μmhos/cm, whereas the average value of TDS is 116,09 mg/L. The value of EC and TDS in the upstream watershed tend to be lower than the value of EC and TDS in the middle and downstream watershed. Hydrogeomorphological factors that control the emergence and characteristic of springs, including rock contact between old vulcanic rocks and limestone, crack structures found in andesitic breccia rocks, and slope class changes between slope 13-20% and 20-55% and 20-55% and 55-140%.