Telaga is a pond formed in the dolines as a result of ponor plugging. A total number of 443 telaga arerandomly distributed within Gunung Sewu Karst (3,200 km2). Telaga used to provide approximately 90%of the local people's water supply (before 1990s). However, most telaga are currently drying up, only 30telaga remain perennial. The environmental problems of the telaga can be grouped into three categories,namely a) diminishing storage, b) rapid water loss, and c) water quality deterioration.

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... nishing storagehas been resulted from rapid sedimentation (caused by extensive agriculture to the karst hills) and theincrease of infiltration (caused by the lost of karst soil cover). Rapid water loss is due to basal leakage(caused by removal of bottom soil during telaga deepening practices or embankment construction) andhigher evaporation (caused by higher wind velocity and warmer local temperature). Water qualitydeterioration has been resulted from multiple usages (human bathing, washing, animal bathing, animaldrinking, fishery) inside the telaga, as a result waste is retained in the telaga water body. Majorcontaminants of telaga water are phosphate, COD, nitrate, detergent, collie bacteria, and suspended solid.Proposed rehabilitation options which may be easily applied among others are, a) leaving the upper slopeof karst hills for perennial crops, b) imposing Guyang Warak tradition, c) sealing telaga bottom with asphalt soaked sacks buried in clay, c) replacing concrete levy with a sandwich of stone pile and clay, d)planting readily consumed perennial crops along telaga sides, and e) establishing simple bathrooms outside telaga so that waste will not remain in the telaga water body.