Thesis (M.S.- Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (p. 143-147).

Thesis (M.A. - Geography and Area Development)--University of Arizona. / Includes bibliographical references (leaves 155-167).

Thesis (Ph. D. - Hydrology and Water Resources) - University of Arizona. / Includes bibliographical references (leaves 214-232).

A 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.

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.

This report is in two parts. The first part covers the ecological processes pertinent to the restoration of Bingham Cienega. The second part presents a subregional groundwater flow model for analyzing the water budget, stream and spring behavior, and water table configuration. Because of the sparsity of ecological and hydrologic data, both parts must be considered as preliminary studies.

abstract: Riparian systems in the arid southwest are heavily altered and, based on relative land-area, provision a disproportionately high number of native wildlife. Amphibians and reptiles are collectively the most threatened vertebrate taxa and, in the Sonoran Desert, are often reliant on riparian habitat. The link between amphibians and environmental water characteristics, as well as the association between lizards and habitat structure, make herpetofauna good organisms for which to examine the effects of environmental change. My objective was to relate capture rates of a fossorial anuran and lizard abundance to aspects of native, invaded, and shrub-encroached riparian habitats in order to forecast the potential winners and losers of riparian habitat xerification and invasion. I measured habitat and monitored herpetofauna at 18 sites near the confluence of the San Pedro River and Gila River in Pinal County, Arizona in 2016 and 2017. Sites were divided into three categories based on dominant tree genus; Populus-Salix, Prosopis, and Tamarix, which represented native riparia, xeric riparia, and invaded riparia, respectively. Habitat measurements indicated that sites varied significantly in structure, and that dominant tree species was a useful descriptor of habitat physiognomy. Results from herpetofauna trapping demonstrated that Scaphiopus couchii, a fossorial anuran, occupy Prosopis sites at a much higher rate than at Tamarix sites, which were almost completely avoided. S. couchii was also found to be closely tied to xero-riparian habitat components present at Prosopis sites and soil analyses indicate that aspects of soil moisture and texture play an important role in the partitioning of this species across altered riparian habitats. Lizard abundance was found to be significantly lower in Tamarix habitat, with the majority of captures attributed to the generalist whiptail Aspidoscelis tigris. Additionally, more than half of lizard species that were analyzed displayed a negative association to Tamarix habitat. Of the three habitat types considered, Populus-Salix supported the greatest abundance of lizards. Based on this study, the deleterious effects of xerfication on a riparian herpetofauna community may be lesser than those of Tamarix invasion. These two forms of riparian habitat shift often co-occur, with the ultimate cause being changes in hydrologic regime. This may imply that a bottom-up approach, wherein historic hydrology is restored to restore or maintain native habitats, to riverine management is appropriate for riparian herpetofauna conservation. / Dissertation/Thesis / Masters Thesis Applied Biological Sciences 2018

Western riparian zones have undergone significant landscape changes over the past several decades, with introduced saltcedar (Tamarix spp.) as a crucial component of this transformation. Saltcedar, now a dominating presence along many western rivers, due to its high tolerance to drought, salinity and stress, is considered to be a high-water-use plant that can desiccate disturbed river systems. Where native and saltcedar plant communities occur together, it is important to understand water use patterns and the physiological responses of each species to environmental stress factors, as a way to project an eventual course of succession processes and management options at a given site. Stress and disturbance in the form of reduced stream flows and land use changes may influence these interactions. Understanding the conditions that allow for saltcedar dominance is critical in determining riparian water budgets, and developing effective management strategies. Sap flux sensors were used to measure the physiological response of co-occurring communities of saltcedar and native trees to these environmental stress factors during the pre-monsoon period in early summer, a time of maximum stress for riparian vegetation. The results suggest that native trees are still competitive with salt cedar so that a mixed plant community is likely to continue on the San Pedro River on the condition that current groundwater levels and river flows are maintained. If base flows and depth to groundwater continue to decline, this competitive balance between saltcedar and native trees likely could change.

No description available.

No description available.