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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Changes in concentration and composition of dissolved and particulate organic matter in the upper San Pedro River, Arizona, in response to changes in flow regimeHaas, Peter Andrew.; Brooks, Paul D. (The University of Arizona., 2003)This study presents the results of 15 months of intensive sampling of the upper San Pedro River at the Boquillas ranch research site. Sampling identified patterns in surface water chemistry associated with seasonal changes in flow regime. The source of organic matter shifted from highly aquatic to highly terrestrial during the monsoon season. Concentrations of Dissolved Organic Carbon (DOC) increased from a nonmonsoon baseflow median of 2.7 ± 0.1 mg/I to a median monsoon baseflow concentration of 3.3 ± 0.2 mg/l. DOC concentrations during flow events were significantly higher (p < 0.05) with a median peak concentration of 7.2 ± 0.4 mg/l. Concentrations of Dissolved Organic Nitrogen (DON) increased from a non-monsoon baseflow median of 0.10 ± 0.01 mg/1 to a median monsoon baseflow concentration of 0.16 ± 0.01 mg/l. DON concentrations during flow events were significantly higher (p < 0.05) with a median peak concentration of 0.48 ± 0.02 mg/l. The 59-day 2002 monsoon contributed 40% of the water volume while transporting nearly 50% of the Dissolved Organic Matter (DOM) and 99% of the Particulate Organic Matter (POM) for the 2002 water year. Annual rates of production were estimated for DOC between 0.008 and 0.0012 g C m^-2yr^-1 and Particulate Organic Carbon (POC) between 0.07 and 0.11 g C m^2 yr^-1 , as well as, DON between 0.00024 and 0.00036 g N m^-2 yr^-1 and Particulate Organic Nitrogen (PON) between 0.004 and 0.006 g N m^-2 yr^-1 . Flux rates were much lower than that of mesic systems and likely reflects the lower terrestrial net primary productivity of the desert environment and below average precipitation during the 2002 water year.
Historical land occupance of the upper San Pedro River Valley since 1870Rodgers, William Maxwell,1907-; Stanislawski, Dan (The University of Arizona., 1965)This study traces the sequence of occupation of the land of the Upper San Pedro River Valley from its beginnings with the discovery and exploitation of its mineral resources through the exploitation of the free open range to eventual necessity to own or lease all grazing lands used. It concludes with a description of the development of small tract suburban residential occupation of significant magnitude since establishment of a payroll source at Fort Huachuca in 1954 and later the growth of popularity for suburban retirement living in Arizona. Concurrent with consideration of the sequence of occupation in the area, the consequences of denudation of the mountain woodlands for fuel prior to 1900 and the disturbance of vegetation and soil of the grasslands due to continuous uncontrolled overgrazing until 1930 is described and discussed. The study concludes that the changes to the landscape of the area since 1870 were directly due to the occupation and use of the land. Denudation of the mountain woodlands and severe disturbance of the grasslands caused significant change to the drainage and moisture content of the soil leading to an invasion of desert shrub into what was once a grass dominated landscape.