An analysis of the effects of retiring irrigation pumpage in the San Pedro riparian national conservation area, Cochise county, Arizona
AffiliationDepartment of Hydrology & Water Resources, The University of Arizona
Arizona Research Laboratory for Riparian Studies
KeywordsWater-supply -- Arizona -- San Pedro Riparian National Conservation Area.
Irrigation farming -- San Pedro River Valley (Mexico and Ariz.)
Groundwater -- San Pedro River Valley (Mexico and Ariz.)
Riparian areas -- San Pedro River (Mexico and Ariz.)
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Collection InformationThis title from the Hydrology & Water Resources Technical Reports collection is made available by the Department of Hydrology & Atmospheric Sciences and the University Libraries, University of Arizona. If you have questions about titles in this collection, please contact firstname.lastname@example.org.
AbstractA seasonal groundwater model was developed to simulate fluxes and head distributions with periodic boundary conditions within the San Pedro Riparian National Conservation Area (SPRNCA) in southeastern Arizona. This model incorporated a seasonal approach for the period 1940-1995. Two years were used to simulate streamflow, 1990 and 1995. The model, as currently calibrated, does not accurately reproduce observed baseflow conditions in the San Pedro River and simulates an exaggerated effect of retiring irrigation within the SPRNCA. The model simulated increased baseflows while the observed baseflows declined at the USGS Charleston stream gage, though increases in baseflow contributions between Hereford Bridge and Lewis Springs have been reported. The original (Corell, et al., 1996) model and the seasonal transient model suffer from over- estimation of discharge from the floodplain aquifer to the San Pedro river, as well as errors in the seasonal transient model's simulation of riparian ET, and seasonal variations in stream conductance. These problems precluded the seasonal transient model from replicating the observed baseflows in the San Pedro river at the Charleston bridge, however, the results of the simulation are thought to be qualitatively indicative of changes in the flow system resulting from the retirement of irrigated agriculture in the San Pedro Riparian National Conservation Area. Possible sources for this problem include replacement of irrigation stresses by the expansion of cones of depression more distant from the river, overestimation of mountain front recharge, poor baseflow estimates and evapotransipration calculations from the stream gages at Charleston and Palominas, and the effects of a recently discovered silt -clay body that may dampen the speed of the rivers response to changes in stress. Additional efforts to re- calibrate the model, taking these areas into account, should provide better simulated baseflow values of the observed data.
Series/Report no.Technical Reports on Hydrology and Water Resources, No. 00-010
SponsorsThis project was funded by, and this report prepared for the Bureau of Land Management. We are very grateful to many individuals whose support was invaluable to the completion of this project. Stan Leake, of the USGS, Frank Putman of the ADWR, Steve Correll, of Hydrosystem, Inc., and many of Dr. Sorooshian's research group at the University of Arizona.
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Simulation of Groundwater Conditions in the Upper San Pedro Basin for the Evaluation of Alternative FuturesGoode, Tomas Charles; Maddock, Thomas, III; Department of Hydrology & Water Resources, The University of Arizona; University of Arizona Research Laboratory for Riparian Studies (Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ), 2000)The creation of the groundwater model of the Upper San Pedro Basin included two developmental phases: the creation of a conceptual and numerical model. The creation of the conceptual model was accomplished through the utilization of Geographic Information System (GIS) software, namely ArcView, used primarily to view and create point, line, and polygonal shapes. The creation of a numerical model was accomplished by the infusion of the conceptual model into a 3D finite difference grid used in MODFLOW groundwater software from the U.S. Geological Survey. MODFLOW computes the hydraulic head (water level) for each cell within the grid. The infusion of the two models (conceptual and numerical) was allowed through the use of Department of Defense Groundwater Modeling System (GMS) software. The time period for groundwater modeling began with predevelopment conditions, or "steady state." Steady state conditions were assumed to exist in 1940. The steady state was used as the initial condition for the subsequent transient analysis. The transient simulation applied historical and current information of pumping stresses to the system from 1940 to 1997. After modeling current conditions, Alternative Futures' scenarios were simulated by modifying current stresses and by adding new ones. The possible future impacts of to the hydrologic system were then evaluated.