HR: 17:15h
AN: H24F-06    [Abstracts]
TI: Artificial Streams, Distorted Processes: The Effect of Effluent on Stream-Aquifer Interactions
AU: * Treese, S
EM: streese@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, The University of Arizona, 1133 E James E. Rogers Way, Tucson, AZ 85721, United States
AU: Meixner, T
EM: tmeixner@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, The University of Arizona, 1133 E James E. Rogers Way, Tucson, AZ 85721, United States
AU: Hogan, J
EM: jhogan@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, The University of Arizona, 1133 E James E. Rogers Way, Tucson, AZ 85721, United States
AU: McCoy, A
EM: amccoy@email.arizona.edu
AF: Department of Arid Lands, The University of Arizona, 1955 E Sixth Street, Tucson, AZ 85705, United States
AB: Treated wastewater, effluent, has been used as a remedy for overstressed aquifers and dry streambeds. Artificial recharge basins allow effluent to seep into the ground relieving stressed aquifers. These basins however, frequently become clogged due to physical obstacles resulting from chemical and biological reactions. Effluent can also be used to replace baseflow for dry streambeds. However, little is known about the effect of effluent on stream-aquifer interactions. The Upper Santa Cruz River, Arizona has effluent, from the Nogales International Waste Water Treatment Plant, as its dominant water input (excepting flood events). A series of monthly field campaigns were undertaken to understand the impact of effluent on the streambed at 16 different sites along a thirty kilometer stretch of the river. The San Pedro River, Arizona is a natural flow, perennial stream that was also tested monthly and used as a control reach. The field campaigns had two focuses: physical transformations in the streambed and water source identification using chemical composition. Physical transformations were measured through the use of 1) piezometers and seepage pans and 2) soil cores; both used to obtain saturated hydraulic conductivity values (K_SAT) over time. Water sampling included: the monthly field campaigns, monsoon flows, and nearby wells. All samples were analyzed for cations, anions, and stable isotope ratios (δD and δ¹⁸O). Results indicate that the Santa Cruz River becomes disconnected from the aquifer adjacent to the point of effluent discharge. Furthermore, as the time between major flood events increases, the disconnection of the stream and aquifer extends further downstream. In total the results imply that water in the streambed is isolated from the groundwater, perhaps due to clogging and that barrier is removed after especially large flood flows (1000+ cfs).
DE: 1830 Groundwater/surface water interaction
DE: 1834 Human impacts
DE: 1860 Streamflow
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: 2007 Fall Meeting