Ground-water age dating and other tools used to assess land-use effects on water quality

A relatively new method for age dating recent ground water along with other investigative tools improve our understanding of land-use effects on the water quality in a surficial aquifer and adjacent streams in the Red River of the North Basin:

• Ground water commonly takes more than 20 years to reach depths in the surficial aquifer where it is withdrawn for use.
• Water withdrawn from most drinking-water wells was recharged through land areas greater than 1 mile upgradient.
• Because of these long travel times and distances, land-management practices on the land and aquifer-protection strategies may take as much as 50 years to produce measurable improvement in water quality.
• The amount of fertilizer and some herbicides used to enhance crop growth in this study area can be related to the distribution and trends of nitrate and herbicides found in the surficial aquifer.