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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RightsCopyright © Arizona Board of Regents
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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Populus Fremontii Tree Ring Analysis and Semi-Arid River Water Source Variability over Time, San Pedro River, ArizonaMeixner, Thomas; Stolar, Rebecca Ann; Hu, Jia; Niu, Guo-Yue (The University of Arizona., 2019)Summer floods are an important source of sustained streamflow in arid and semi-arid rivers of the American Southwest and Northwest Mexico. The degree to which natural function versus human alterations influence the system is subject to debate. Environmental information in the tree ring cellulose of Populus can be used to investigate the variation in water sources over time in these areas. Past research has shown that streamflow sources in the San Pedro Basin of Arizona vary isotopically between a source water of basin ground water and a summer flood water source. This study uses isotopic analyses of Populus fremontii and atmospheric data in the San Pedro Basin to estimate the water source of the trees and the river water source condition. After analyzing weather data within the basin, an inversion of the Barbour oxygen isotope model using tree ring cellulose isotopes was used to obtain the water source isotopic composition. The variation in water source composition inferred from the model was then compared to the river composition over time. It was initially found that each site’s water source isotopic composition was significantly different from the source water. However, several water source isotopic compositions were found to be more negative than the known basin groundwater signature in each of the study sites. Following sensitivity analyses on various parameters within the model, it was seen that relative humidity has a strong influence on the determination of source water. Therefore, relative humidity must be an accurate measurement and is not considered to be so in this study. Furthermore, in order to understand the degree to which natural function versus human alterations influence the system, older Populus fremontii tree ring isotopes are needed, posing a question regarding the reliability of the species.
Comparison of measured hydraulic properties to predicted values of the upper San Pedro watershed, ArizonaFerre, Paul; Olander, Anastasia; Ferre, Paul (The University of Arizona., 2004)An understanding of the distribution and ranges of hydraulic and physical properties of the subsurface sediments in the Upper San Pedro Subwatershed in Southwestern Arizona is needed to estimate infiltration and recharge rates to the aquifer system. The objectives of this thesis are to compare measured saturated hydraulic conductivity values to standard references and to test available predictive models of soil hydraulic properties based on particle size distributions against hydraulic properties measured directly on undisturbed cores. Hydraulic and physical properties compared well to standard references. The predictive models compared well with sand type sediments, but did not compare well with those cores with large percentages of clay and silt. A conclusion is that predictive models may not produce adequate results to estimate infiltration and recharge rates to an aquifer system if the subsurface sediments have large percentages of clay and/or silt. Furthermore, exclusion of large percentages of gravel may produce inaccurate results for physical and hydraulic properties.