HR: 16:30h
AN: H54D-03    [Abstracts]
TI: Water Quality Significance of Wetlands Receiving Agricultural Drainage
AU: * Stringfellow, W
EM: wstringfellow@lbl.gov
AF: Environmental Engineering Research Program University of the Pacific, School of Engineering & Computer Sciences Sears Hall 3601 Pacific Ave, Stockton, CA 95211, United States
AU: * Stringfellow, W
EM: wstringfellow@lbl.gov
AF: Lawrence Berkeley National Laboratory, Ecology Department MS 70A-3317, Berkeley, CA 94720, United States
AU: Sharon, B
EM: seborglin@lbl.gov
AF: Environmental Engineering Research Program University of the Pacific, School of Engineering & Computer Sciences Sears Hall 3601 Pacific Ave, Stockton, CA 95211, United States
AU: Sharon, B
EM: seborglin@lbl.gov
AF: Lawrence Berkeley National Laboratory, Ecology Department MS 70A-3317, Berkeley, CA 94720, United States
AU: Engelage, S
EM: SKEngelage@lbl.gov
AF: Lawrence Berkeley National Laboratory, Ecology Department MS 70A-3317, Berkeley, CA 94720, United States
AU: Hanlon, J
EM: jshanlon@lbl.gov
AF: Environmental Engineering Research Program University of the Pacific, School of Engineering & Computer Sciences Sears Hall 3601 Pacific Ave, Stockton, CA 95211, United States
AU: Graham, J
EM: jgraham@pacific.edu
AF: Environmental Engineering Research Program University of the Pacific, School of Engineering & Computer Sciences Sears Hall 3601 Pacific Ave, Stockton, CA 95211, United States
AU: Burks, R
EM: rburks@pacific.edu
AF: Environmental Engineering Research Program University of the Pacific, School of Engineering & Computer Sciences Sears Hall 3601 Pacific Ave, Stockton, CA 95211, United States
AB: The San Joaquin Valley is one of the most productive agricultural regions in the world and this productivity is heavily dependent on irrigated agricultural. An inevitable consequence of irrigated agricultural is the generation of return-flows conveyed down-gradient in agricultural drains that eventually discharge to surface waters. Agricultural drainage often has poor water quality characteristics, but demand for water in California is high and agricultural drainage is often diverted for secondary use, including the maintenance of ponds and wetlands. Additionally, agricultural drainage often discharges into riparian wetlands, rather than into the open river channel. In this study we tested the hypothesis that wetlands were mitigating or buffering the impact of agricultural drainage and that discharge of agricultural drainage into wetland buffer zones would provide water quality benefits. Water samples were collected at wetland, agricultural, and mixed drainages in the San Joaquin River basin and analyzed for a broad array of physical and chemical water quality parameters, including nutrients and organic carbon. At selected wetlands, input-output studies were conducted to determine wetland specific water quality effects. The water quality of drainages influenced by wetlands was compared to drainages that were predominantly influenced by other types of land-use. Wetland influenced drainages are more likely to have higher DOC concentrations that other drainages, including agricultural and mixed urban-agricultural drains. Wetland dominated drainages had lower nitrates than agricultural drainages and studies of individual wetlands demonstrated that wetlands remove soluble phosphate and nitrate, but produce DOC and biochemical oxygen demand (BOD). Overall land use in a drainage was a less significant determinant of water quality than soil type and the presence or absence of wetlands. The specific trihalomethane formation potential (THMFP) of the DOC from wetland dominated drainage waters was not significantly different than the specific THMFP for agriculturally derived DOC. The biodegradation potential for the THMFP was also similar between the different drainage sources, suggesting that there is not a biologically recalcitrant DOC fraction contributing disproportionately to specific THMFP in wetland drainage. Results to date suggest that the THMFP of wetland carbon can be mitigated by biological degradation as would occur in natural ecosystems. Nutrient enrichment of the San Joaquin River is an significant regional water quality problem and diversion of agricultural drainage through wetlands before discharge reduces nutrient loads to surface waters. However, potential waster quality gains from nutrient removal are offset by increases in DOC and associated BOD. The overall benefit of diverting agricultural drainage through wetlands is being investigated in the context of competing water quality priorities and the desire to expand riparian habitat in the San Joaquin Valley.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1831 Groundwater quality
DE: 1834 Human impacts
DE: 1847 Modeling
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Fall Meeting