The city of Yogyakarta, central Java, received approximately 50 mm of fine ashfall from the 13 February 2014 eruption of Kelud volcano in east Java.
Many residents and businesses in Yogyakarta rely on an extensive system of shallow wells for their water supplies. These wells are typically five to six metres deep and one to 1.5 metres in diameter and constructed of concrete. An estimated 30% of the ~15,000 wells in Yogyakarta are open-air and uncovered. Media reports indicated that uncovered wells in Yogyakarta were contaminated' by volcanic ash from the Mt Kelud eruption, and well owners were urged by the agencies BPBD and BLH (the environment agency) to check the cleanliness of their wells.
The agency BBTKL-PPM conducted a water quality survey to assess impacts of the Kelud eruption in the Yogyakarta area. The main effect on water quality noted in the shallow wells following the Kelud eruption was that some wells became 'cloudy' (i.e. turbid). No other effects on water chemistry were noted. For turbidity removal, the chemical flocculant polyaluminum chloride (PAC) was distributed. This chemical is stocked in community health centres.
| Dosage of coagulant/litre1 | Dosage of disinfectant/litre | ||||
| Clarity of water | PAC (g) | Soda ash (g) | Alum (g) | Quicklime (g) | Chlorine2 (g) |
| Clear | - | - | - | - | 0.002 |
| Moderately clear | 0.05 | 0.05 | 0.15 | 0.05 | 0.002 |
| Cloudy | 0.1 | 0.1 | 0.3 | 0.1 | 0.002 |