- What are the issues with agricultural runoff?
Agricultural runoff triggers significant problems that range far beyond the dozen or so yards adjacent to where it enters the stream. Excess nutrients in runoff provides opportunities for algae and vegetative pests like duckweed to quickly take over, eventually shading out and suffocating creatures that make up the aquatic ecosystem, along the entire food chain, including non-aquatic insects, pollinators, and larger wildlife that consume fish as a major portion of their diets. Downstream, deadly algae blooms can seriously harm recreational and commercial fishing areas, and damage drinking water sources hundreds of miles away.
Pesticides, herbicides, and other chemicals can also be washed away with runoff from fields and other agricultural operations. If it doesn’t enter local waterways or evaporate, it will typically soak into the ground, where it may carry those pollutants into the groundwater, degrading the quality of drinking water, especially for those residents who draw their water directly from wells or local surface waters.
- How do farmers prevent agricultural runoff?
As the environmental damage attributed to agricultural runoff becomes more apparent and concerning, farmers have begun to use a variety of green management techniques to reduce and manage runoff. Increasingly precise, overhead, irrigation techniques, such as drip irrigation, allow farmers to apply just enough water to support the needs of their crop, without producing excess that can flow off the surface of the fields. In the Midwest, the installation of tile drainage systems allow crops to absorb water through their roots by artificially raising and lowering the water table as needed.
Cover crops, prairie strips, and grassed waterways are in-field techniques that divert runoff and minimize pollution by both disrupting and slowing the flow of water and anchoring the soil and their nutrients in place.
Filter strips placed adjacent to tilled fields act as collection centers for runoff that can then be diverted to saturated buffers, sediment control basins, two-stage ditches and wetlands that remove sediment and pollutants through natural physical and biological processes.
Other management options include no-till practices, planting stream-side trees and shrubs, and leaving other native buffers between tilled fields and streams. Physical barriers that prevent livestock from disturbing the banks of streams and lakes minimize physical damage and eliminate pollution from animal waste.
- What impact does farm runoff have on inland and coastal waters?
Across the US, problems associated with soil erosion and the nutrients, pesticides, and other contaminants associated with agricultural runoff constitute the country’s primary source of water quality impairment. According to the EPA, about 46% of our rivers and streams have excess nutrients, and only 28% are assessed as “healthy”. 21% of our lakes have high levels of algal growth and 39% have measurable levels of a cyanotoxin. Around 21% of coastal waters have high nutrient levels, while other waters have high levels of sediment and bacteria. The levels of contamination found in our primary sources of drinking waters represent serious human health hazards. The damage inflicted on commercial fishing, shrimping and shellfish farming creates massive economic hardships and impacts the availability of all types of seafood.
- How does water recycling improve food security?
Farmers who install on-farm reservoirs and include treatment elements like wetlands, saturated buffers, and bioreactors are able to exert a greater measure of control over their water supplies. These reservoirs can be directly managed by individual farmers, who can then prioritize the use and distribution of the stored water for irrigation. A farmer’s ability to provide even moderate, supplemental irrigation during critical growth periods, when rainfall may be entirely absent, allows them to maximize crop yields and ensure reliable, consistent production.
Unlike farmers who are dependent on costly, inconsistent, and increasingly limited water withdrawals from rivers or public or privately owned reservoirs, those who capture and store water during rainy periods are establishing their operations as a means of long term, sustainable food production. This is important because climate scientists project, and we are already seeing, changes in precipitation patterns characterized by intense rainfall events punctuated by dry periods. These changes inevitably impact the productivity of rainfed crop systems around the country and around the world, and by extension, the global issue of food security.
- Why are drainage tiles an environmental issue?
The use of drainage tile systems can be credited with establishing the US Midwest as one of the most intense regions of agricultural production in the world. As a nation, the U.S. produces around a third of the world's corn and soybeans, and more than 80% of those corn and soybeans come from the Midwest, making the region a key player in the global food system. So, while it’s true that the practice of manipulating the water table on Midwest farms can cause environmental issues, it’s perhaps a more valuable goal to seek to mitigate those issues than to eschew the use of tile drainage altogether.
Because tile drainage works by manipulating portions of the local water table, its use may produce unintended consequences like draining valuable wetlands, impacting critical habitats and biodiversity in some of the most productive ecosystems in the world. Often compared to rain forests and coral reefs. When water drains through the soil in agricultural fields, it enters the drainage system loaded with nutrients. When this nutrient-laden water is discharged to ponds, small lakes, and rivers, it puts them at an increased risk for harmful algal blooms, which can not only destroy aquatic ecosystems and negatively affect wildlife dependent on them, but if it enters groundwater or downstream drinking water sources, it can expose human populations to toxins that are known to cause liver damage and cancer.
