As Arizona enters the 1980's, we see that population growth, economic expansion, and resource depletion go hand-in-hand. Non-renewable groundwater-reserves in Arizona are being extracted at rates that cannot long continue without incurring serious consequences, economic as well as environmental. Growth of irrigated agriculture in the alluvial basins of the state, growth of urban and suburban populations, and,growth of industrial pumping, especially for copper mining -milling and for cooling of electric power generation facilities, have incurred a heavy draft on the state's aquifers. The net result of such ground-water withdrawals has been the "mining" of underground water reserves, a continuing overdraft in excess of natural replenishment, and steadily dropping water tables. This rate of depletion of ground water is generally considered to be the most serious water problem in Arizona. It is by no means the only problem. We must be concerned also with maintenance of water quality in view of existing and potential pollution; administrative systems for equitable and efficient water allocation and use; and the legal and environmental aspects of water acquisition and utilization.In order to assess present and possible future water conditions in the state relative to growth, water resources will be viewed from the standpoint of (1) water usage, both quantitative and qualitative; (2) conservation of water; (3) availability of water; and (4) projected water needs.

Project Completion Report, OWRT Project No. A-056-ARIZ / Agreement No. 14-31-0001-5003 / Project Dates: July 1974 - June 1975 / Acknowledgement: The work upon which this report is based was supported by funds provided by the State of Arizona and the United States Department of the Interior, Office of Water Research and Technology as authorized under the Water Resources Research Act of 1964. / Specific objectives of the project included (1) examining the effect of pit recharge, using industrial blowdown effluent, on local ground-water levels and quality in the Tucson basin; and (2) evaluating the applicability of two digital models for modelling the hydraulic response of the aquifer to pumping and recharge. Fourteen pit trials ranging from 1 day to 185 days duration were implemented during a two year period. The total volume of effluent recharged was 157 ac-ft. Pit recharge on a limited basis did not appear to offset the general decline in local ground -water levels. However, recharge deteriorated the quality of ground water in shallow (150 ft) wells but not in a deeper (300 ft) well. A finite difference (FD) model and a finite element model (FEM) were used to simulate hydraulic conditions in a 2000. ft by 2000 ft aquifer region near the pit. An attempt was made to calibrate the models using water level data from a two-week aquifer test on a shallow well. Results were depicted using a three-dimensional graphics technique (SYMVU). Better results were obtained with the FD model than with the FEM, primarily because a finer mesh was used to discretize the region with the FD model than with the FEM. Results of the FEM were also biased by the rectangular configuration of the aquifer boundary. The finite element model was used to simulate aquifer response during a pit recharge test. Again, results were limited by the injudicious selection of elements and boundary configurations.

Geologic applications of Landsat images in northeastern Arizona to the location of water supplies for municipal and industrial uses / A Final Report of Work Performed Under OWRT Matching Grant B-066-ARIZ, Agreement number: 14-34-0001-8060 / April 1979

The overall objectives of a study initiated in 1972 by the Water Resources Research Center (Univ. of Arizona), in cooperation with the Pima County Dept. of Sanitation, are to examine the possibility of interactions between recharged river water and deposits in adjoining landfills, and if such interactions occur to evaluate the effect on native groundwater quality. Corresponding to these objectives, the principal function of a monitoring program initiated during the project was to characterize background water levels and native groundwater quality during normal low flows (i.e., sewage flows) in the river, and to monitor changes, if such occur, during flood flows. As it turns out, data from the project should also be applicable to the anticipated irrigation of farmland near Marana, using effluent from the Impending Ina Rd Treatment Facility. In particular, clues will be provided on transformations in sewage effluent quality during infiltration and deep percolation. The first phase of the project was conducted at the Ina Rd landfill and the second involved both the Ina Rd and Ruthrauff Rd fills. Results of the first phase were reported in a paper by Wilson and Small. This report will review the results of the second study phase. Specific objectives of the studies during the second phase included (1) obtaining river water and well water samples for chemical and microbiological analysis, (2) monitoring water level changes in available wells and (3) characterizing general features of the geohydrology in the vicinity of the landfills.

No description available.

The Tucson Basin is a semi-arid alluvial basin in southeastern Arizona in which the Santa Cruz River, an ephemeral stream, flows south to north with its flows resulting directly from rainfall. The City of Tucson discharges treated sewage effluent into the bed of the Santa Cruz and to some irrigated farms. Previous investigations indicate that sewage effluent is recharging the Tucson Basin Aquifer with the water spreading horizontally in the Fort Lowell Formation. The ¹⁸0/¹⁶0 ratios determined in water samples by the author support the findings of these previous investigations. Sewage effluent had an average δc0-18 value of -7.9 per mil and water samples from the north Santa Cruz wells had an average δc0-18 value of -9.3 per mil. Up hydraulic gradient, the ¹⁸0/¹⁶0 ratios are lighter indicating that sewage recharge water has mixed with ground water. In the case of one well in the mixed zone, it is calculated that approximately 70 percent of the water comes from sewage recharge and 30 percent from normal ground water. Recharge water spreads horizontally in the Fort Lowell Formation up to two miles on each side of the river. The δc0-18 values of water samples from the south Santa Cruz wells averaged -8.9 per mil and compared closely to the average δc0-18 values for summer flows in the Santa Cruz River of -8.2 per mil.

No description available.

FLUMP, a recently developed mixed explicit -implicit finite -element program, was calibrated against a data base obtained from a portion of the Tucson Basin aquifer, Arizona, and represents its first application to a real -world problem. Two previous models for the same region were constructed (an electric analog and a finite -difference model) in which calibration was based on prescribed flux boundary conditions along stream courses and mountain fronts. These fluxes are not directly measured and estimates are subject to large uncertainties. In contrast, boundary conditions used in the calibration of FLUMP were prescribed hydraulic heads obtained from direct measurement. At prescribed head boundaries FLUMP computed time - varying fluxes representing subsurface lateral flow and recharge along streams. FLUMP correctly calculated fluctuations in recharge along the Santa Cruz River due to fluctuations in storm runoff and sewage effluent release rates. FLUMP also provided valuable insight into distributions of recharge, discharge, and subsurface flow in the study area.Properties of FLUMP were compared with those of two other programs in current use: ISOQUAD, a finite -element program developed by Pinder and Frind (1972), and a finite- difference program developed by the U.S. Geological Survey (Trescott, et al., 1976). It appears that FLUMP can handle a larger class of problems than the other two programs, including those in which the boundary conditions and aquifer parameters vary arbitrarily with time and /or head. FLUMP also has the ability to solve explicitly when accuracy requires small time steps, the ability to solve explicitely in certain parts of the flow region while solving implicitly in other parts, flexibility in mesh design and numbering of nodes, computation of internal as well as external fluxes, and global as well as local mass balance checks at each time step.

This work examines the hydrogeochemical evolution of Tucson basin groundwater, including isotope hydrology, geochemistry and age determinations. Results of mineralogic investigation on basin fill were used to constrain water-rock geochemical reactions. Examination of 45 years of water quality data shows that groundwater mining has affected water quality. Stable isotopes of carbon, oxygen, hydrogen, sulfur, and chlorine and radiocarbon, tritium and radon determinations refine the interpretation of hydrogeochemical evolution of Tucson basin groundwater as modelled with NETPATH. Two distinct sampling periods, the first in 1965 and the second between 1984 and 1989, resulted in the determination of groundwater ages for water mined two decades apart. Isotope hydrology and geochemical modelling suggest that much of the water presently mined from the Tucson basin has a component recharged during the last 50 years. Increased sulfate concentrations suggest that heavy pumping in the northeastern basin may have induced increased leakage from lower units. Results of geochemical modelling indicate an average of 5 percent mountain-front recharge to the Ft. Lowell Formation along the northern aquifer margin. An increase in dissolved solids along the basin margin implies that this component to recharge has increased in the past decade. The radiocarbon age of the basin groundwater was compared with the temporal movement of water as modelled with MODFLOW and PATH3D. In general, the hydrologic simulation agrees with both the distribution of tritium and the exponentially modelled water age, as determined with bomb-derived radiocarbon, for areas of the Tucson basin that contain water less than 50 years in age. Hydrologic modelling failed to predict the antiquity of recently sampled water in the central basin but is similar to age determinations on waters collected in 1965.

The concept of hydrochemical facies is used to study the distribution and, indirectly, to identify the origin of the chemical character of ground water in the basin-fill aquifer of the Tucson Basin in relationship to the hydrogeologic framework. Hydrochemical fades of ground water is defined operationally in terms of the lateral (horizontal) variation of chemical quality. The following chemical constituents are included in this study: total dissolved solids, calcium, magnesium, sodium, potassium, chloride, sulfate, bicarbonate, pH, nitrate, fluoride, strontium and zinc. A conceptual process-response model relates the regional distribution of dissolved constituents to the following hydrogeologic controls: (a) the chemical composition of the rock and soil in the drainage area before recharge to the ground-water basin and conditions at the recharge sites, (b) the lithology of the basin-fill aquifer, and (c) the direction of groundwater flow within the aquifer itself. Trend surface analysis suggests that the regional distribution patterns of total dissolved solids, calcium, sodium, sulfate and strontium show a tendency to parallel the direction of ground-water flow. The distribution pattern of chloride ions based on old analyses shows a trend opposite to the distribution pattern of chloride ions based on new analyses from the same area. Nitrate content of ground water and specific capacity of wells seem to be related. Q-factor analysis of data from the basin-fill aquifer demonstrates that the overall chemical character of the ground water does not change substantially as it moves through the basin. It is concluded that the chemical character of ground water in the basin-fill aquifer of the Tucson Basin was acquired mainly during contact with various rock types in the drainage basin before recharge. The lithology of the aquifer, presumably, only plays a secondary role in determining the overall chemical composition of the ground water. After recharge to the basin-fill aquifer the distribution of dissolved constituents is controlled primarily by the flow pattern. A chemical equilibrium model of calcite and water is used to approach the problem of determining whether precipitation or dissolution of calcite takes place in the aquifer. Measured calcium ion concentrations and pH values are compared to calcium ion concentrations and pH values computed for the equilibrium model. Assuming that the equilibrium model represents actual conditions in the aquifer, departures from the equilibrium model may be used to predict the chemical behaviour of calcite In the basin-fill aquifer.