HR: 17:00h
AN: H32H-05    [PDF]
TI: Hydrological and Biogeochemical Connectivity Between Uplands, Vernal Pools, and Streams, Great Central Valley, California
AU: * Rains, M C
EM: mrains@cas.usf.edu
AF: Department of Geology, University of South Florida, 4202 E. Fowler Avenue, SCA 528, Tampa, FL 33620 United States
AU: Fogg, G E
EM: gefogg@ucdavis.edu
AF: Department of Land, Air, & Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616 United States
AU: Harter, T
EM: thharter@ucdavis.edu
AF: Department of Land, Air, & Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616 United States
AU: Dahlgren, R A
EM: radahlgren@ucdavis.edu
AF: Department of Land, Air, & Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616 United States
AU: Williamson, R J
EM: rjwilliamson@ucdavis.edu
AF: Department of Land, Air, & Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616 United States
AB: Vernal pools are depressional wetlands that are inundated for portions of the wet season, then drain and dry in the late wet and early dry seasons. During portions of the wet season, surface water often flows out of vernal pools to down-gradient aquatic systems such as streams. A common conceptual model of vernal pool hydrology is that vernal pools fill largely due to direct precipitation and drain and dry largely due to evapotranspiration. However, this conceptual model may be largely incorrect for vernal pools occurring on duripans, perhaps the most common type of vernal pool in the Great Central Valley, California. In this presentation, we will present evidence that suggests that vernal pools occurring on duripans are integral surface water components of seasonal, perched surface water and groundwater flow systems, and that the hydrogeological characteristics of these seasonal, perched surface water and groundwater flow systems play important roles in determining biogeochemical function. Groundwater is recharged by annual rainfall, perches on the duripan, and flows down gradient toward a seasonal stream. Groundwater flows through the vernal pools, with groundwater discharge occurring at the up-gradient end of the vernal pools and groundwater recharge occurring at the down-gradient end of the vernal pools. Surface water also flows through the vernal pools, with surface water flowing out of the lowest vernal pool through an outlet swale to a seasonal stream. However, groundwater discharge occurs along the length of the outlet swale, and surface water discharged to the seasonal stream is largely upland groundwater discharge rather than vernal pool surface water discharge. At the pool scale, the biogeochemical functions of individual vernal pools are easily quantified since it is clear that nitrate and, presumably, phosphate are uptaken and that dissolved organic carbon is produced. However, at the catchment scale, the biogeochemical functions of individual vernal pools are not easily quantified since it is equally clear that surface water discharged to the seasonal stream is largely upland groundwater discharge rather than vernal pool surface water discharge.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1871 Surface water quality
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2003 Fall Meeting