The Relationship of Land Use and Groundwater Quality: A Case Study of Rhode Island

Abstract

The quality of groundwater used for drinking is critical to consumers. Due to the nature of groundwater flow, pollution source control is important for groundwater protection. Point and nonpoint pollution sources are closely related to land use. The pollution sources that originate from particular land uses must be identified and controlled to prevent degradation of groundwater quality. This research is a study of the relationship between groundwater quality and land use in Rhode Island State. Water quality data were collected from twenty-one public drinking water wells and land use data were interpreted from air photos. Water quality data and land use data from 1970 and 1988 are compared to analyze the change of land use and change of groundwater quality. The study areas are within a 1,000 foot radius around each well. Land use types include commercial/industrial, residential, undeveloped, and agricultural land. Road systems are also considered as a factor in this study. A computerized Geographic Information System (ARC/INFO) has been applied in the study. Several statistical methods have been used to analyze the relationship between land use and groundwater quality. The water quality data in 1988 indicate that nitrate and chloride do not pose a threat to groundwater in Rhode Island. However, sodium levels are likely to cause water quality problems at some public drinking water wells. The analysis demonstrates that the nitrate, chloride, and sodium concentrations in groundwater in 1988 were greater than that in 1970. This indicates that groundwater among the study wells has degraded over the study period. The study determined that undeveloped areas around study wells decreased significantly from 1970 to 1988. The result shows that most new development in these area had converted undeveloped land into residential, commercial, or industrial land. The study has found that the areas of residential land use and surface water are related to increases in the levels of chloride and sodium concentrations in the wells. Nitrate concentrations in the wells are closely related to increased areas of residential land and paved light duty roads. It can be concluded from the research that urbanization has an impact on groundwater quality. Attention should also be given to the area beyond the 1,000 foot limit. Further studies will need to include more independent variables and more valuable findings are expected by increasing the sample size.