Three methods to remove nitrates from the agricultural drainage water from the San Luis Service Area in California were investigated. One method was a theoretical evaluation of nitrate removal by algae during the transport of the drainage water in the San Luis Canal or during storage in the Kesterson Reservoir. The other methods were designed to promote anaerobic bacterial denitrification in a continuous flow of drainage water. One method used barley straw and the other water grass grown in shallow ponds as the carbon energy source. Under optimum conditions both of these last two methods reduced the nitrate -N concentration of the drainage water from a maximum of about 30 mg/l to less than 2 mg/l. The cost of nitrogen removal by the shallow grass plot systems, the most economical and feasible method investigated, was estimated.