On the surface, Ag doesn't pollute water
By: Don Curlee

A recent study of water quality by resource economists at the University of California indicates that agriculture doesn't deserve its bad rap for contaminating surface water.

However, it suggests that agriculture is just as much at fault as other sources for the contamination of groundwater.

Research for the study indicates that only a very small portion of common water pollutants can be positively correlated with agricultural production. The majority of pollutants have no relationship to agriculture at all.

Some of them are even negatively correlated, which means the water quality is better because of agriculture.

Study results

The report was completed by Hossein Farzin, a professor in the Department of Agricultural Resource Economics, or ARE, at University California, Davis, and Kelly Grogan, a Ph. D student in ARE at UC Davis. It was published in ARE's Update for July/August.

They measured water quality indicators commonly reported by the eminent state and federal agencies dealing with water quality and maintained by the federal Environmental Protection Act, or EPA.

They sampled surface water in California counties that are leaders in agricultural production for levels of 15 pollutants that might occur from four sources: natural (nonhuman), industrial, agricultural and household. The statistical samples of the pollutants were taken from a base of sensitive data called STORET maintained by the EPA.

It includes updated water quality information from sources such as the California Department of Water Resources, the EPA National Aquatic Resources Survey, the California Surface Water Monitoring Program, the California State Water Resources Control Board and the National Park Service.

The study measured the reported levels of 15 pollutants from ammonia, arsenic and copper through nitrates and nitrites to total coliform, total suspended solids and zinc. Only specific conductivity and sulfates registered a positive impact of crop intensity, while copper levels measured negative.

In areas of animal intensity only magnesium and nitrites had a positive effect on surface water quality, while dissolved oxygen was on the negative side in these locations.

The authors of the study placed significance on the lack of correlation between the intensity of agriculture and pollutants such as ammonia, arsenic, mercury, total coliform and zinc.

"This suggests that due to health hazards of these toxins, mitigatory measures already in place work adequately, and policy should address the non-agricultural sources of these pollutants," they said.

Additionally, the report said: "This study shows that agriculture is not the main culprit of some typical agricultural pollutants found in surface water. We find that crops do not contribute to total suspended solids and that animal production even appears to decrease TSS."

However, the study found that surface water pollutants such as nitrites, nitrates, sulfates, phosphorous and specific conductivity are significantly positively correlated with agricultural production.

The authors concluded that these pollutants should be targeted by agriculturally related surface water quality programs, especially in counties with high agricultural intensities.

Groundwater quality programs, the authors suggest, may need to study a wider range of pollutants.

To put it all in perspective, it appears that swimming in the state's rivers, lakes, streams and ponds is not only permissible, but entirely safe. When water is pumped from the underground it will be a good idea to monitor its quality before swimming in it, drinking it or bathing your pets in it.

Apparently, washing your car with it is okay.