Contrasting water quality from paired domestic/public supply wells, Central High Plains

Closely located domestic and public supply wells were sampled using identic al sampling procedures to allow comparison of water quality associated with well type. Water samples from 15 pairs of wells with similar screened inte rvals completed in the central High Plains regional aquifer in parts of Kan sas, Oklahoma, and Texas were analyzed for more than 200 water quality cons tituents. No statistically significant differences were observed between th e concentrations of naturally-derived constituents (major ions, trace eleme nts, and radon) in paired wells. However, differences in water quality betw een paired wells were observed for selected anthropogenic compounds (pestic ides and tritium), in that some public supply wells produced water that was more recently recharged and contained constituents derived from surface ac tivities. The presence of recently recharged water and compounds indicative of anthropogenic activities in some public supply wells was likely due to operational variations (pumping rate and pumping cycles), as demonstrated i n a particle tracking simulation. Water containing surface-derived anthropo genic compounds from near the water table was more quickly drawn to high vo lume public supply wells (less than five years) than domestic wells (greate r than 120 years) with small pumping rates. These findings indicate that wa ter quality samples collected from different well types in the same area ar e not necessarily directly comparable. Sampling domestic wells provides the best broad-scale assessment of water quality in this aquifer setting becau se they are less susceptible to localized contamination from near the water table. However, sampling public supply wells better represents the quality of the used resource because of the population served.