The quality of water delivered by the city of Lincoln is affected by seasonal concentrations of herbicides in water from the Platte River, especially during spring and early summer. Filtration through valley sediments reduces herbicide concentrations to less than half of the original amount in the river. This mixing decreases the concentrations of herbicides in drinking water about another 50 percent. The quality of the drinking water also is affected by water demand. Water demand increases during the growing season, especially during hot and dry weather, more than 1 month after the largest concentrations tend to occur in the river.
Greater demand requires a larger percentage of collector-well water.
This potentially reduces the quality of the drinking water because the water from the collector wells is more affected by the surface water than the vertical wells, and the surface water tends to be more contaminated than the ground water. Degradation of herbicides during transport in soil, river, and aquifer and during the ozonation process in treatment plants results in the formation of by-products. The health risk of the by-products of herbicides naturally created in the environment and during the ozonation process have not been studied fully. Small herbicide concentrations in water from the collector wells can be limited through well-field management. The rest of the water pumped by the collector wells is ground water containing small herbicide concentrations.