Hydrogeological surveys have been carried out in the Borobudur area and its surroundings, the northern part of the West Progo Hills to the Magelang intermountain plains. The purpose of this study is to determine the variations in groundwater’s chemical types in the study area and to interpret the hydrochemical processes. Primary data was taken in the field, including groundwater data and rock petrology. Physical / chemical data of groundwater were obtained from laboratory test results. Data analysis includes hydrochemical analysis using the Stiff, Piper, and Durov diagrams. The result shows that groundwater in the study area has a wide variety of chemical types, namely Ca, Mg - bicarbonate; Ca, Mg, alkaline – bicarbonate; Alkaline, Ca – chloride, and Alkaline - chloride. Groundwater in the study area is fresh (type Va) to brackish (type Vc), with low -moderate TDS content (119 - 6,810 ppm), and soft calcium carbonate hardness (6.0 - 16.6 ppm). Hydrochemical processes occur in groundwater are simple dissolution and cation exchange caused by clay materials originating from Quaternary deposits or weathering of Old Andesite Formation volcanic breccia. In addition, the presence of brackish water in Karangrejo and Candirejo may be triggered by mixing with fossil water.

Groundwater in the Banjararum area is found in various rocks that build  the West Progo Hills, including the Nanggulan and the Andesite Breccia Formations. Groundwater can be found in dug wells and springs. Field surveys show that the groundwater is generally clear, tasteless and odorless, except for the well at Ngipikrejo. Chemical test results from four samples showed that groundwater in limestone has Ca, Mg - HCO3 type, whereas in volcanic rocks of type Ca - HCO3 and Ca, Na - HCO3. Groundwater chemistry type is generated from the soil, mineral dissolution in sedimentary rocks and igneous rocks as well as the atmosphere through rainwater. The considerable content of NO3 in the Ngipikrejo area indicates pollution from human activities, plants or animal dung. In general, groundwater in the study area is suitable for use as clean water or drinking water, characterized by a measurable pH in the field of 6.6 - 7.2 and TDS 54 - 155 ppm. Nevertheless, laboratory test results show that groundwater samples are water-filled, with a hardness of 135,866 - 778,048 (moderately hard - very hard), so special treatment is required before drinking.

Survei airtanah di bidang kimia isotop dilakukan di daerah Banjararum Kabupaten Kulon Progo. Pengamatan mataair Degan dan Dukuh dan sampling dua contoh airtanah dari mataair secara langsung di lapangan dilakukan untuk mengetahui karakteristik isotop airtanah di daerah tersebut. Metode penelitian adalah survei airtanah dan uji laboratorium isotop. Data yang dibutuhkan meliputi data fisik/kimia dan kandungan isotop airtanah. Analisis kandungan isotop airtanah dilakukan guna mendukung pemahaman genetika airtanah dengan melihat variasi kandungan hidroisotopnya. Hasil penelitian menunjukkan bahwa di daerah penelitian diketahui adanya airtanah dengan karakter isotop stabil yang ringan maupun berat. Kandungan isotop yang ringan di daerah Degan menunjukkan bahwa presipitasi sangat berperan dalam mempengaruhi kualitas airtanah setempat. Sementara itu, mataair di daerah Dukuh menunujukkan genetik airtanah yang lebih kaya isotop, dan dapat diinterpretasikan adanya  interaksi water-rocks yang lebih kuat, khususnya dari batuan karbonat Formasi Jonggrangan yang kemungkinan dilewati aliran airtanah setempat.