Urbanization accelerate the growth of population in Yogyakarta. The existence of densely populated settlements directly affect the river environment Code. Some residents still dispose liquid waste into the river that contribute to polluting the environment. Slums also lead to environmental health problems. Pollution is not only happen in the river, but also occurs in wells population. The problem is compounded by the condition of the terraced river border. Waste from septic terrace 1 (top) and terrace 2 (middle) will flow into the patio 3 (bottom) and pollute wells population in the terrace 3 (bottom) as the accumulation of septic tank waste originating from above. The purpose of this study was to determine the condition of the water quality of wells in terracedareas, based on parameters DO, pH, electrical conductivity (DHL), temperature, TDS, and E-Coli bacteria as well as to ascertain whether there is a direct correlation of pollution accumulation from high to lower elevation on a terraced area. Methods being used include: Identification of wells and sanitation, wells positioning measurements with GPS, plotting the location of wells to map, collecting sample from wells, analyzing the quality of well water in the laboratory, and analyzing the well water contamination. Based on the results, it can be concluded that there are decline in water quality, either on the left or on the right side of the river. In other words, there is a direct correlation between contamination accumulation of well water at a high elevation and a lower elevation on the terraced riverbank area code.