Kualitas Airtanah di Dataran Borobudur Kabupaten Magelang Propinsi Jawa Tengah =

The aims of this research are : 1) to understand groundwater quality distribution in Borobudur Plain2) to analyze the relationships between population density and groundwater quality in Borobudur Plain. A collection of field data has been done with the help of topographic map, geologic map, landform map and land use map from previous research. A collection of geological data includes observation kind of stones, relation, and thickness. Groundwater data collection i.e. temperature measurement, pH, electrical conductivity, water level, and depth of the well has been done as random sampling method in Borobudur Plain. Sampling for groundwater chemical and biological analysis used stratified random sampling from electrical conductivity group with range less than 500 pmhos/cm, 500-1000 iimhos/cm and more than 1000 pmhos/cm. Chemical and biological analysis is meant for making an illustration groundwater quality in Borobudur Plain. The result of this research showed that groundwater quality in Borobudur Plain is distinguish on four lithological units, i.e.: 1) silty sandstone unit, which is formed from recurrence silty sandstone, tuff siltstone, conglomerate, fine-coarse tuff sandstone with inserted young Merapi breccia2) tuff sandstone unit, which is formed from tuff sandstone with recurrence tuff3) colluvial deposit unit, which is formed from free material silt to boulder grain size4) alluvial deposit unit, which is formed from free material fine sand to cobble. Tuff siltstone as impermeable layer forms the boundary groundwater in Borobudur Plain, as an unconfined groundwater and a confined groundwater. Both groundwater from unconfined and confined aquifer are used as people groundwater resources. The region was arranged silty sandstone unit i.e. Wanurejo, Candirejo, and Ngargogondo that decreasing groundwater quality than Bumiharjo, Borobudur, and Tanjungsari until very dangerous if used drinking water. This showed that maximum drinking water quality standard for drinking water is showed DHL, Cat., Fe, NO3-, Cl- found at silty sandstone unit in Candirejo, Wanurejo, and Ngargogondo. Relationship between population density and groundwater quality showed that increasing population density at settlement land use in Borobudur Plain cause decreasing groundwater quality if the water is used for drinking water, especially shown by coliform concentrations. Settlement land use as the high population density cause groundwater quality decreasing. Key words : groundwater characteristics - population density -groundwater qualit