An analysis of the effects of retiring irrigation pumpage in the San Pedro riparian national conservation area, Cochise county, Arizona
Affiliation
Department of Hydrology & Water Resources, The University of ArizonaArizona Research Laboratory for Riparian Studies
Issue Date
2000Keywords
Water-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.)
Groundwater.
Irrigation farming.
Riparian areas.
Water-supply.
Metadata
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Copyright © Arizona Board of RegentsCollection Information
This 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 repository@u.library.arizona.edu.Abstract
A 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. 00-010Sponsors
This 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.Collections
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TRANSIENT ELECTROMAGNETIC (TEM) INVESTIGATIONS INTHE UPPER SAN PEDRO RIVER BASIN, BENSON, ARIZONATransient Electromagnetic (TEM) surveys were conducted in the San Pedro Valley starting approximately 1 mile northeast of Benson, Arizona, and extending about 2 miles farther northeast. The survey used loop sizes of 20x20, 100x100, and 200x200 meters with the objectives of determining the depth, thickness, and lateral extent of clay deposits, and comparing ground surveys with a previously acquired airborne TEM survey. The data were processed with Zonge Engineering smooth inversion software as well as Interpex TEMIX layered-earth inversion software. The interpreted depth to near-surface clay deposits was less than 5 m on the west end near the San Pedro River, and increased to about 15 m, 1.3 km to the east. Farther east, clay deposits were only detected at depths of 100 m or more. A possible bottom to the clay was detected near 100 m depth at selected stations in the western half of the survey, which would correlate with wells in the vicinity, but it was not laterally continuous. Surveys at the remainder of the stations did not detect a lower limit to the clay deposit. The results of the airborne survey versus the ground elevation surveys show similar resistivity values.
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Flow model for the Bingham cienega area, San Pedro river basin, Arizona: a management and restoration toolA finite element groundwater flow model was used to support a hydrologic assessment for a study area in the Lower San Pedro River Basin which contains the Bingham Cienega. Consolidated sedimentary rocks associated with an extension of the Catalina Core Complex truncate the floodplain aquifer system in the study area. The elevated water table produced by this "hardrock" results in spring discharge at the cienega and a locally gaining reach of the San Pedro River. The steady -state model suggests that recharge (and discharge) components for the floodplain aquifer sum to 3.10 cfs. Mountain front recharge, underflow, and stream leakage are the primary recharge mechanisms, while stream leakage, evapotranspiration, spring flow, and underflow out are sources for groundwater discharge. A steady -oscillatory model was used to account for seasonal periodicity in the system's boundary conditions. Monthly variation in the evapotranspiration rate was offset primarily by storage changes in the aquifer. Due to a lack of measured hydrologic data within the study area, results from the model simulations are only preliminary. Model development and the subsequent sensitivity analyses have provided insight into what type of data needs to be collected. Head measurements are most needed in the area just downstream from Bingham Cienega. The mountain front recharge and evapotranspiration rates are shown to be highly sensitive parameters in the model; improved estimation of these values would be helpful. Spring discharge would be a valuable calibration tool if it could be accurately measured. A more extensive record of stream baseflow in the San Pedro River should be established. After more hydrologic data is collected, the model could be recalibrated so as to better represent the system. Eventually, this tool may be used in direct support of management and/or restoration decisions.
