Farm Runoff

Both upstream of downtown Walla Walla and after the city, Mill Creek is lined by farms. The farm fence pictured here was less than 30 feet away from the water, just east of Walla Walla Community College. 

There are lots of plants around the edge of the water, acting as a barrier between the runoff from the farms and the creek. What could the consequences be if those did not exist? In many areas, they don't have proper filtering systems for runoff from agriculture before it reaches a water source. 

Agriculture runoff is considered a nonpoint source pollutant because it come from a wide area of land. In 2003, the Environmental Protection Agency established a number of measures to be used to help control this runoff. These documents can be found here:

http://water.epa.gov/polwaste/nps/agriculture/agmm_index.cfm

There area  variety of additives in the runoff from farms. They include pesticides, herbicides, and fertilizers. Pesticides and herbicides create problems for obvious reasons: they are toxic and can often times kill the organisms living in the water. Fertilizer is a more complex pollutant. The fertilizer is comprised of nitrogen, phosphates, and potassium, in a variety of proportions. These act as nutrients to the plants on the farms, and continue to act as nutrients to plants as they are brought into the rivers from runoff. This gives algae and other plants in the water extra growing ability. Bacteria begin to eat away at the algae, and in doing so they also use up the dissolved oxygen in the water. 

The main effects of this situation are an increase in turbidity, due to the extra plant growth and the bacterial waste, and a lower dissolved oxygen content. 

One of the easiest and most effective ways to prevent this runoff is to plant a barrier between water (such as lakes and rivers) and farmland. It is important to use native plants because they will have the ability to allow for percolation of the runoff, instead of having the runoff sit in the top layer of the soil. 

Sources:

United States Environmental Protection Agency. (2013, September 09). Water: Polluted runoff. Retrieved from http://water.epa.gov/polwaste/nps/agriculture.cfm