HR: 09:30h
AN: H51J-07    [Abstracts]
TI: Significance of Overland Flow in Sustaining Water Resources of Arid and Semi-Arid Rivers - Water Quantity and Quality Implications
AU: * Meixner, T
EM: tmeixner@hwr.arizona.edu
AF: University of Arizona, Hydrology and Water Resources/SAHRA, Tucson, AZ 85721, United States
AU: Hogan, J F
EM: jhogan@hwr.arizona.edu
AF: University of Arizona, Hydrology and Water Resources/SAHRA, Tucson, AZ 85721, United States
AU: Brooks, P D
EM: brooks@hwr.arizona.edu
AF: University of Arizona, Hydrology and Water Resources/SAHRA, Tucson, AZ 85721, United States
AU: Oelsner, G P
EM: goelsner@hwr.arizona.edu
AF: University of Arizona, Hydrology and Water Resources/SAHRA, Tucson, AZ 85721, United States
AU: Soto-López, C D
EM: csoto@hwr.arizona.edu
AF: University of Arizona, Hydrology and Water Resources/SAHRA, Tucson, AZ 85721, United States
AU: Baillie, M N
EM: baillie@nmt.edu
AF: New Mexico Institute of Mining and Technology, Earth and Environmental Science, Socorro, NM 87801, United States
AU: Simpson, S C
EM: simpson@hwr.arizona.edu
AF: University of Arizona, Hydrology and Water Resources/SAHRA, Tucson, AZ 85721, United States
AB: Overland flow is known to be a dominant runoff generation mechanism in arid and semiarid river systems. Despite its prevalence, little is known about the impact of overland flow on the quantity and quality of water in arid and semi-arid rivers and riparian systems. Several studies along the San Pedro and Rio Grande Rivers in the Southwest United States have documented the importance of ephemeral overland flows to the quantity and quality of river water in the stream and near stream zones. First, studies on both rivers have documented the importance of flood flows in providing a significant source of water to near stream aquifers. On the San Pedro River studies have shown that ~50% of baseflow water originates from summer Monsoon floods with a stronger influence on losing versus gaining river reaches. In the Rio Grande, stable isotope data indicate that nearly 100% of the increase in discharge during a Monsoon flood event can be attributed to ephemeral overland flow with approximately 40% of this flood pulse in the Rio Grande lost to the shallow alluvial aquifer. Second, nutrient studies on both rivers demonstrate that reconnecting the river with its uplands during flood events causes a dramatic increase in nutrient concentrations and fundamentally alters near and in-stream biogeochemical conditions and processes by providing a large pulse of allochthonous nutrients and organic matter. Despite the large nutrient influx with flood events the sustained impact on nutrient composition is limited; with upwelling zones, possibly reworking particulate organic matter, having more influence than water source on in-stream nutrient concentrations. Furthermore the influence of flood events attenuates significantly over a period of months with the influence of flood events diminishing from 40% of river flow to 20% in a period of just 6 months.
UR: http://hwr.arizona.edu/tmeixner
DE: 1806 Chemistry of fresh water
DE: 1830 Groundwater/surface water interaction
DE: 1850 Overland flow
DE: 1856 River channels (0483, 0744)
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Fall Meeting