A comprehensive methodology of hydraulic testing in fractured rocks is presented. The methodology utilizes geological and geophysical information as background. It consists of conventional single-hole packer tests in conjection with a newly developed cross-hole packer test. The cross-hole method involves injecting fluid into a packed-off interval in one borehole and monitoring hydraulic head variations in packed-off intervals in neighboring boreholes. Borehole orientation is unrelated to the principal hydraulic conductivity directions which, therefore, need not be known a priori. The method yields complete information about the directional nature of hydraulic conductivity in three dimensions on a scale comparable to the distance between the test boreholes. In addition to providing all six components of the hydraulic conductivity tensor, the cross-hole method also yields the specific storage of the fractured rock mass. While the theory behind this method treats the rock as a homogeneous, anisotropic, porous medium, the test provides detailed information about the degree to which such assumptions may actually be vaild in the field. The method may also be useful as a tool for detecting, in the vicinity of the test area, major fractures or faults that have not been intercepted by boreholes. Preliminary results from a granitic site near Oracle in southern Arizona are presented together with details of the instrumentation designed and constructed specifically for that site.

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.

No description available.

A study of the Salt River Indian Reservation in central Arizona evaluated pre-development hydrologic conditions with an emphasis on simulating ground-water flow conditions within the reservation, where data was scarce before extensive aquifer pumping began in 1940 in adjoining portions of the East Salt River Valley. Water-resource development began in the valley with the completion of the Tempe Canal in 1871. Additional canals and irrigated agriculture spread quickly in areas along the Salt River, which has a mean annual flow of about 1.25 million acre-feet. Pre-development ground-water flow was horizontal and steady-state. The simulation indicated that the available water-level data, though corrupted in areas adjacent to the river, more properly described the virgin system than flow estimates. Sensitivity analyses indicated that simulated heads on the reservation were sensitive to all processes except evapotranspiration. Recharge through the riverbed, evapotranspiration, and subsurface outflow were all co-dependent.

The Arizona Nature Conservancy's Hassayampa River Preserve is 50 miles northwest of Phoenix near the town of Wickenburg. Four miles of the largely ephemeral Hassayampa River are perennial within the preserve, supporting one of the finest remaining cottonwood-willow forests in the state. Stream flows are affected by wells pumping ground water directly from the alluvial aquifer and may be influenced by wells which intercept lateral inflow from the regional basin-fill aquifer. Developing effective management strategies to protect base flow conditions (∼4 cfs) depends on a clear understanding of the surface and ground-water systems in the preserve. Provided that ground water developers near Wickenburg recognize and incorporate the interconnected nature of each hydrologic system, perennial flow within the preserve is not believed to be immediately threatened. (Abstract shortened with permission of author.)

Down-hole injection and sampling equipment was designed and constructed in order to perform diverging-flow tracer tests. The tests were conducted at a field site about 8 km southeast of Oracle, Arizona, as part of a project sponsored by the U. S. Nuclear Regulatory Commission to study mass transport of fluids in saturated, fractured granite. The tracer injection system was designed to provide a steady flow of water or tracer solution to a packed off interval of the borehole and allow for monitoring of down-hole tracer concentration and pressure in the injection interval. The sampling system was designed to collect small volume samples from multiple points in an adjacent borehole. Field operation of the equipment demonstrated the importance of prior knowledge of the location of interconnecting fractures before tracer testing and the need for down-hole mixing of the tracer solution in the injection interval. The field tests were designed to provide data that could me analyzed to provide estimates of dispersivity and porosity of the fractured rock. Although analysis of the data is beyond the scope of this thesis, the detailed data are presented in four appendices.

Many hydrologic basins in the southwest have seen their perennial streamflows turn to ephemeral, their riparian communities disappear or be jeopardized, and their aquifers suffer from severe overdrafts. Under -management of ground -water exploitation and of conjunctive use of surface and ground waters are the main reasons for these events.

Arizona is presently in the midst of a general adjudication for the Gila River system -- the watershed which comprises the southern two- thirds of the state. The purpose of the adjudication is to prioritize all water claims in the river system: both state -established and federally reserved rights. Arizona adheres to a bifurcated (or divided) system of water law which only recognizes a component of ground water -- called subflow -- to be appropriable. Wells which pump non-appropriable water -- called tributary flow -- are not to be included in the adjudication. The problem is that federal laws do not recognize this artificial bifurcation. The challenge lies in identifying a subflow zone which satisfies the hydrologic fiction of existing state precedents and the hydrologic reality of federal statutes. At the core of the problem lies the fate of Arizona's perennial stream water and the fulfillment of federally reserved tribal water rights. Thus, larger questions loom: can Arizona law reconcile its glutinous past with a water -scarce future, will the adjudication ever reach a finality, and even if it does, will it be a finality that all sides can live with?