Sources of Pollution from Agricultural Drainage

In response to Public Law 92-500, a National Pollutant Discharge Elimination System (NPDES) permit program for irrigated agriculture was developed by California in 1974. Approximately 3,000,000 acres (1,200,000 ha) are now under permit. The NPDES permit contains a self-monitoring program that is carried out by water purveying and drainage organizations. Monitoring during the first 2 yr was limited to measurements of flow, salinity, and suspended solids for supply and discharge waters. The information provided by the monitoring program has provided baseline date for surface waters utilized by irrigated agriculture. Since some agricultural discharges have been shown to exceed water quality objectives of surface waters in California, best management practices are being developed in pollution control. Sediment problems are being dealt with by 208 planning sediment control programs while salinity discharge problems are being considered by the Inter-Agency Drainage Program and may also be handled in some areas by 208 planning.