Research Signpost 37/661 (2), Fort P.O. Trivandrum-695 023 Kerala, India Agricultural Drainage Ditches: Mitigation Wetlands for the 21 st Century, 2010: 173-194 ISBN: 978-81-308-0376-0 Editors: Matthew T. Moore and Robert Kröger 8. Water quality changes occurring in agricultural drains of varying riparian function William Stringfellow 1,2,4 , Justin Graham 1 , Mathew Rogers 2 , Sharon Borglin 1,2 Mark Brunell 3 , Jeremy Hanlon 1,2 , Chelsea Spier 1 and Kennedy Nguyen 1 1 Ecological Engineering Research Program, School of Engineering & Computer Science, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211; 2 Lawrence Berkeley National Laboratory Earth Sciences Division, 1 Cyclotron Road, Berkeley, CA 94720; 3 Department of Biological Sciences, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211. Abstract. Agricultural drainage is a major source of diffuse pollution in the United States and worldwide and nutrient enriched agricultural drainage is a contributing factor to the widespread eutrophication of anthropogenically impacted rivers and estuaries. The addition of edge of field vegetation and grass “filter-strips” has been promoted as a best management practice (BMPs) for preventing the entry of nutrients, sediments and other pollutants into agricultural drainage ditches. More recently, it has been proposed that improving riparian function in agricultural drainages would have a purifying effect on drainage water, in a similar manner to treatment wetlands. In this study we examined the changes in concentration of nitrate, soluble reactive phosphate (SRP), and total suspended solids (TSS) that occurred in agricultural drains at five study sites with varying amounts of riparian function, in the San Joaquin Valley of California. Riparian habitat quality was measured using the California Rapid Assessment Method (CRAM) for Wetlands. We tested the hypothesis that Correspondence/Reprint request: Dr. William Stringfellow, Ecological Engineering Research Program, School of Engineering & Computer Science, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA E-mail: wstringfellow@lbl.gov