Comparison of measured hydraulic properties to predicted values of the upper San Pedro watershed, Arizona

Abstract

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.