Sediment and nutrient losses from an irrigated watershed.

Irrigated agriculture is an essential part of stable food and fiber production. However, water returning from irrigated watersheds can contain excess sediment, nutrients and salts. Applying polyacrylamide to furrow irrigated fields reduces erosion 60 to 90%. Converting from furrow irrigation to sprinkler irrigation eliminates planned irrigation runoff necessary for uniform water application. Installing sediment ponds removes 50 to 80% of the suspended sediment from water before it flows back to major water bodies. In southern Idaho, irrigation watershed monitoring showed that implementing these conservation practices has reduced average suspended sediment loss from 460 kg/ha in 1970 to less than 100 kg/ha in 2005. These practices, however, have had less effect on soluble nutrients. Median nitrate concentrations have almost doubled from 1970 to 2005. Current research is focusing on identifying practices to reduce soluble nutrient losses.