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.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1982. / Includes bibliographical references (leaves 159-162).

Thesis (Ph. D. - Renewable Natural Resources)--University of Arizona, 1988. / Includes bibliographical references (leaves 153-166).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1988. / Includes bibliographical references (leaves 115-117).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 113-117).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1987. / Includes bibliographical references (leaves 149-151).

The Swedish Nuclear Fuel and Waste Management Company, SKB, is planning to construct a deep geological repository for spent nuclear fuel in Forsmark, Sweden. Leakage of groundwater into the repository during the construction and operational phases might cause a groundwater drawdown that in turn may affect the hydrological conditions in sensitive habitats in the area. The sensitive habitats in question are wetlands, home to several protected species. SKB has planned to take mitigation measures in the case variations of the surface-water elevation are identified for the concerned wetlands. The mitigations measures consists in infiltrating water in the ground in the direct vicinity to the wetland to create a higher groundwater pressure that then will propagate to the surface-water. This study describes the modelling of a pilot-study of such a measure and aims at serving as one of the background materials for the planning and design of the pilot study. The aims of the pilot study are to show that the surface-water level in a wetland can be controlled and to gain knowledge and experiences regarding artificial groundwater recharge for this purpose. The pilot study would take place before the construction of the repository so the undisturbed case is considered. The results show that an infiltration facility can control the surface-water level in a wetland. It is also shown that an infiltration rate of 0.5 L/s is enough to manipulate the surface-water level in the undisturbed condition.

A geochemical approach to the evaluation of the chemistry of natural recharge processes in the Tucson basin was used to identify the major minerals controlling the evolution of ground water chemistry and to assess the viability of recharging imported Central Arizona Project water supplies. Well cuttings analyses and water quality samples from over 65 wells in the basin were used as input to the geochemical computer model PATH4 (Helgeson, 1970) and the sequence of aqueous species and mineral production in a recharge reference volume examined. The study reveals that natural processes in the basin lead to the increase in dissolved solids content in ground water over time and the production of secondary minerals such as calcite, calcium montmorillonite, kaolinite and poorly crystallized alumino-silicate phases. Secondary minerals grow into aquifer pore spaces and may, over time, be responsible for the reduction in aquifer porosity and the specific capacity of wells. The recharge of imported Central Arizona Project water will lead to an increase in the dissolved solids content of ground water and may, in certain areas of the basin, lead to the enhanced production of secondary minerals. The use of CAP water as a recharge source must be guided by the geochemical factors which influence the nature and scope of reactions between CAP water and the Tucson aquifer matrix. The study demonstrates the need for and identifies water quality and aquifer matrix criteria for the assessment of sources of recharge water and recharge facility sites. The use of geochemistry as a tool for quantitatively assessing ground water quality is demonstrated.

The variably saturated flow model Unsat 2 was used for three case study simulations of dry well recharge in the Tucson Basin, Arizona. Dry well design, and rainfall/runoff and vadose zone conditions representative of the locality were assumed in the simulations to address travel time to the regional aquifer, rates and extent of radial flow, and relative degree of solute attenuation by sorption and dilution with regional groundwater. Soil specific surface was used to estimate relative degree of sorption among the three cases. One case of uniform soil composition and two cases of layered soil composition were simulated. Clay content had the greatest influence on specific surface. Hydraulic conductivity had the greatest influence on soil water velocities and degree of radial flow. The presence of layered subsurface conditions that included strata of low hydraulic conductivity enhanced the degree of subsurface solute attenuation by sorption and dilution.

The purpose of this study was to determine if the chloride to bromide ratio (Cl/Br) of water imported via interbasin transfer can be used to trace the mixing of imported water with native ground water. Laboratory experiments and a chemical literature review indicate that chloride's and bromide's properties should make the Cl/Br a useful environmental ground-water tracer. This study has shown that the Cl/Br can be accurately quantified at environmental levels, is not attenuated by aquifer or soil media, is chemically stable, and is present in different levels in waters from different sources. Infiltration and mixing of irrigation water from the Colorado River (Cl/Br = 1300) with native ground water (Cl/Br = 630) was investigated at the Wellton-Mohawk Irrigation and Drainage District near Yuma, Arizona. The downgradient increase in the Cl/Br is correlated with distance from the upgradient limit of irrigation (r =.83), reflecting the chemical influence of infiltrating irrigation water.