From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / From the establishment of the Arizona resources board in 1928 until the Arizona Water Commission was formed in 1971, no state water plan was developed. Since 1971, the longest and most intensive planning studies have been concerned with allocation of Colorado River water through the central Arizona project. Future plans involve desalting sea water, weather modification, importation of water, etc. The Arizona state water plan ultimately will be a plan of management of Arizona's limited water resources. Water plans and economic and environmental impact evaluations are scheduled for completion by july, 1977.

From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / Pinal County is one of Arizona's largest farm and highest farm income areas. Agriculture there is completely dependent upon irrigation systems, with nearly all of the water supply pumped from underlying groundwater reservoirs. Delivery of central Arizona project water will not assure groundwater conservation at a one to one trade-off ratio. Most of the monetary benefits to agriculture derived from the project will be realized by Indian farmers. Cotton acreage will not be affected, but the acreage of small grains and alfalfa will increase. The increasing salinity of cap water should be of no concern to Pinal County farmers.

From the Proceedings of the 1977 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 15-16, 1977, Las Vegas, Nevada / An economic evaluation of the Central Arizona Project was conducted with a goal of developing a simulation model of CAP costs, water operations and capital repayment alternatives. This model was compared to the actual cost experience of the Metropolitan Water District of Southern California for a realistic assessment. In addition, an effort was made to consider some of the indirect impacts of the CAP, and the overall economic outlook was summarized. In devising the simulation model CAP capital costs, CAP power supply and CAP water supply factors were considered along with user charges, management alternatives, and operations, maintenance and repair costs.

From the Proceedings of the 1977 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 15-16, 1977, Las Vegas, Nevada / The purpose and operation of the Central Arizona Project water allocation model system are described, based on a system analysis approach developed over the past 30 years into an interdisciplinary science for the study and resolution of complex technical management problems. The system utilizes mathematical and other simulation models designed for computer operations to effectively solve such problems as the CAP faces including those concerned with social and economic considerations. The model is composed of two major components: (1) a linear program designed to determine the optimal allocation of all sources of water to all demands and, (2) a hydrologic simulator capable of reflecting the impact of distribution alternatives on per-unit cost of delivery. The model, currently being use, has substantially contributed to a greater understanding of water usage potential in Arizona.

The Big Horn Mountains are a geologically complex range that extends over 500 square km in west-central Arizona. Three major lithologic terranes outcrop: (1) Proterozoic amphibolite, phyllite, schists, gneiss, and granite; (2) Mesozoic monzonite to diorite intrusives; and (3) Cenozoic mafic to silicic volcanic rocks and clastic rocks. The entire area is in the upper plate of a detachment fault and, consequently, contains many low- to high-angle normal faults. Each lithologic terrane has its associated mineral occurrences. The Big Horn district is exclusively hosted in the pre- Tertiary terrane. Most of its mineral occurrences are spatially related to the Late Cretaceous intrusive rocks. One occurrence, the Pump Mine, may be a metamorphic secretion deposit, and therefore, would be middle Proterozoic. The vast majority of the mineral occurrences in the Big Horn Mountains are middle Tertiary in age and occur in three districts: the Tiger Wash barite - fluorite district; the Aguila manganese district; and the Osborne base and precious metal district. Fluid inclusions from Tiger Wash fluorite (T(h) 120 to 210° C, NaCl wt. equivalent 17 to 18 percent not corrected for CO₂) and nearby detachment - fault- hosted Harquahala district fluorite (T(h) 150 to 230° C., NaC1 wt. equivalent 15.5 to 20 percent not corrected for CO₂) suggest cooling and dilution of fluids as they are presumed to evolve from the detachment fault into the upper plate. Mass-balance calculations suggest that the proposed evolution of fluids is sufficient to account for the observed tonnage of barite and fluorite. The Tiger Wash occurrences grade directly into calcite- gangue-dominated manganese oxides of the Aguila district. A wide range of homogenization temperatures (T(h) 200 to 370° C.), an absence of CO₂ and low salinities (NaC1 wt. equivalent 1 to 2 percent) in the Aguila district calcite-hosted fluid inclusions argue for distillation of fluids during boiling or boiling of non saline-meteoric waters. Mass - balance calculations modeling the evolution of Ca and Mn during potassium metasomatism of plagioclase in basalt suggest that little if any influx of these cations is necessary to form the calcite –dominated manganese oxide tonnage observed. The Aguila district grades directly to the east into the base-metal and precious-metal occurrences of the Osborne district. Preliminary data describing geological settings, fluid inclusions, and geochemistry suggest that the Osborne district has a continuum between gold-rich to silver-rich epithermal occurrences. The gold-rich systems have dominantly quartz gangue, with or without fluorite, and are hosted in a variety of rocks, but are proximal to Precambrian phyllite or mid-Tertiary rhyolite. Fluid inclusions from two occurrences representative of the gold -rich systems spread across a minor range (T(h) 190 to 230° C., NaC1 wt. equivalent 17 to 23 percent not corrected for CO₂). Dilution of highly saline fluids is the inferred mechanism for precipitation of gold in the gold-quartz systems. The silver-rich systems have dominantly calcite gangue with or without quartz, and are hosted in mid-Tertiary basalt. Calcite fluid inclusions from a representative high-silver occurrence display a wide range of homogenization temperatures and salinities (T(h) 120 to 370° C., NaC1 wt. equivalent 7 to 23 percent). Boiling and consequent neutralization of acidic solutions is the inferred mechanism for the silver-rich, calcite gangue systems. A model inferring a regional fluid-flow regime and local sources of metals is proposed. Four possible regional and local causes of fluid flow in upper-plate detachment regimes are proposed: (1) regional elevation of geothermal gradients as a result of middle-crustal, lower-plate rocks rising to upper crustal levels; (2) meteoric water recharge along the southeast flank of the Harquahala antiform and consequent displacement of connate waters in the upper-plate of the Big Horn Mountains; (3) local emplacement of feeder stocks to rhyolitic flows; (4) and tilting of major upper-plate structural blocks.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The Colorado River is the only major stream in the U.S. whose water supply is fully utilized. This distinction has brought the Colorado more than its share of controversy, within states, between states and between nations. The Colorado River compact, whose purpose was to equitably apportion the waters between the upper and lower basins and to provide protection for the upper basin through water reservation, was ratified by all states except Arizona, in 1923. Arizona finally ratified it in 1944. The history of controversies and negotiation concerning the compact are outlined through the supreme court decision on march 9, 1964, which entitled California to 4.4 maf, Nevada to 0.3 maf and Arizona to 2.8 maf, of the first 7.5 maf available in the lower Colorado. Unfortunately, the court did not attempt to establish priorities in the event of shortage. The problem is complicated by an international treaty of 1944, guaranteeing Mexico 1.5 maf annually, except in years of unusual circumstances. Because Senator Connally of Texas was then chairman of the senate foreign relations committee and because the treaty allocated twice as much Colorado River water to Mexico as it was then using, it was argued that this treaty represented a tradeoff to Mexico, giving it less water from the Rio Grande in exchange for more water from the overburdened Colorado. Problems of inter-basin water transfer studies, uniform Colorado basin water quality standards and central Arizona project planning are discussed.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / Southwestern rivers are few in numbers and low in discharge. The physiographic and climatic reasons for this are discussed. To the east of the 100th meridian, rainfall is reliable and agriculture is stable; while to the west, there is a chronic deficit of water, droughts are frequent and lifestyles must be accordingly adjusted. Dam building results in greatly increased silting behind the dam in both the river and its tributaries and accelerated channel erosion below the dam. Total flow must also decrease due to withdrawals and increased evaporation from reservoirs. The correction of apparent errors in measuring the virgin flow of the Colorado River now indicates that this flow is about 15 maf/yr. Current legal allocations total 17.5 maf/yr of river water, including the central Arizona project (cap), which will withdraw 1.2 maf/yr. While the river is being dammed and overallocated beyond all reason, the water table is being mined at the alarming rate of 20 ft/yr. In central Arizona, it has dropped to about 250 ft below the surface, and even if all withdrawals ceased immediately, it would take many centuries of of desert rains before it would return to its former level of 50 ft. The cap water will cancel only about 1/2 of this overdraft annually. A glance at the phoenix area today shows that rain follows neither the farmers plow nor the subdividers bulldozer.