This paper evaluates the historical growth of the Las Vegas Wash, its subsequent degradation, and the current efforts to restore and stabilize its channel. The Las Vegas Valley Metropolitan Area is located in the Mohave Desert in a drainage basin surrounded by mountain ranges. This drainage basin and its dynamic system of stream channels constitute the Las Vegas Watershed in which the Wash is located. The condition of the Las Vegas Wash is unique, as is a perennial stream that evolved from an ephemeral wash in response to the rapid urbanization and subsequent production of treated wastewater input into the stream channel. The situation has created a series of wetland ecosystems along the Wash, and valuable riparian habitat in such an arid environment. The Wash and its associated wetlands system provide a variety of ecological services to the city of Las Vegas, including storm water conveyance, wastewater effluent filtration, flood protection, and a green space for residents to enjoy. However, continuous increase in volume and intensity of the stream flow has resulted in severe channel degradation and bank erosion in numerous locations along the stream channel. After an examination of the historic and present-day conditions of the Wash and its restoration activities, this essay suggests that future evaluations of the Las Vegas Wash case study may provide evidence to support the propagation of collaborative management efforts.

Ecological restoration has yet to gain an indepth understanding of the social dynamics that inform restoration design and enable improved watershed performance in urban environments. The Rio Salado Environmental Restoration Project is unique in that the scale of the project expands to new reaches of the Salt River with each successful venture. The 40-year project has been most successful in recent years due to innovative strategies that capitalize on public outreach and inclusion. Adoption of multi-purpose objectives that include partnerships, public stakeholders, and learning achievement have contributed to the project's success. The ability of the restored system to withstand flood events is one of the many examples demonstrating the project's qualifications as a model for future urban restoration efforts. Lessons about the social dynamics that inform urban restoration success have the potential to augment scientific learning in ecological restoration.

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General water rights adjudications are now taking place in Arizona. The Gila River and Little Colorado River adjudications are among the largest court proceedings ever undertaken in the United States, involving more than 78,000 water rights claims scattered over 50,000,000 acres of land. The cost of individually proving such a number of individual claims in a formal trial setting would be enormous — often greater than the water's economic worth. Also, the time required to complete such a proceeding would take decades. Consequently, alternative procedures are needed to streamline the investigations and forestall a potentially serious water resource management problem. There are an estimated 22,800 stockwatering ponds (stockponds or stocktanks) in the Gila River Basin alone, and each potentially could be tried as an individual case. If small claims such as those for stockwatering could be considered de minimis in their impact on other higher priority uses, they might be adjudicated as one class of use, thereby fore-stalling a case-by-case trial of each individual water right claim. However, a major obstacle in granting special treatment to small claims lies in demonstrating to litigants that certain small water uses do not, in fact, have a discernible impact on other downstream water right holders. This study was undertaken to quantify the actual losses to a river system from stockwatering ponds, and to compare those losses to other naturally occurring impacts on the hydrologic system. Employing a watershed model, portions of the Walnut Gulch Experimental Watershed at Tombstone, Arizona, an area located within the San Pedro watershed, were analyzed. Storm runoff was simulated with and without the presence of stockponds. Different storm events and storage conditions were modeled in order to measure the impact of stockpond storage under a wide range of field circumstances. This study demonstrated that the hydrologic effects of stockwatering ponds are de minimis with respect to their impact on other water users many tens or hundreds of miles downstream on the river system. Stockpond numbers, capacities, volume/surface area relationships, quantification methods, and effective retention are also evaluated. Statutes in other states are reviewed for their approach to handling stockwatering uses.

The Santa Cruz River in southeastern Arizona is typical of large rivers of the semiarid southwestern United States. The 390-kilometer long river displays great variability in morphology, hydraulics, hydrologic, conditions, and bank stability, reflecting incomplete integration of the drainage system and the disequilibrium that is often characteristic of desert channels. Spatial variability is paralleled by temporal variability at all scales, from instantaneous conditions to millenia of geologic history. The alluvial history of the Santa Cruz River drainage basin suggests that transverse sediment transport toward the valley across alluvial fans has dominated fluvial processes for most of the history of the basin. No evidence is apparent for external drainage of the basin before the beginning of Fort Lowell Formation deposition, about 2.0 to 2.5 million years ago. The mid to late Pleistocene history of the system is poorly understood because of the paucity of the geologic record for this period. Several episodes of terrace formation apparently represent climatically induced sediment pulses and subsequent incision. The Holocene record of the Santa Cruz River suggests a major change in hydrologic regimen about 5,000 years ago when deposits indicate a substantial decrease in stream power. The last 2,500 years are marked by a sequence of channel cut and fill episodes similar to the historic episode of channel entrenchment that began in the 19th century. The hydrologic regimen of the Santa Cruz River is dominated by the occurrence of floods in direct response to precipitation. Three major storm types—monsoonal, frontal, and dissipating tropical—account for most streamflow. The storms cause floods with distinctly different characteristics. Monsoonal storm-caused floods may have quite high peak discharges, but are local and of short duration. Frontal and tropical storms cause floods of longer duration and flood volume and are more efficient agents of sediment transport and geomorphic change than are those caused by monsoonal storms. Geologic controls are the major factor governing the spatial variability of channel morphology and change. Hydrologic factors control the temporal variability of channel processes. Frontal and tropical storms are more likely to produce floods capable of causing and maintaining a continuously entrenched main channel. Floods caused by monsoonal storms do not appear capable of maintaining such a system.

In-situ copper leaching at BHP Copper's San Manuel open pit mine was established in 1986. Currently, over a thousand wells on the benches of the open pit mine are simultaneously injecting and pumping sulfuric acid solutions. A large-scale reconfiguration of the well field in 1996 led to a dramatic, yet temporary, increase in copper pounds, apparently due to changes in flowpaths. While the first reconfiguration was accomplished by means of hydrologic intuition, a question arose regarding the issue of whether subsequent reconfigurations supplemented with additional smaller scale characterization could ultimately lead to increased copper production. To study this question, two fifty-well sites were selected within the in-situ leach well field. Because in-situ leaching involves the movement of fluid within the subsurface, hydrology is a natural context in which to study the process. The desire to optimize well-to-well in-situ leaching for enhanced copper recovery through the fundamental understanding of important hydrologic mechanisms is the primary motivation for this dissertation. Hydrologic testing in San Manuel is inherently challenging due to the hydraulically dynamic environment. A hydraulic cross-hole testing procedure termed "Cyclic Pulse Testing" (CPT) was used to overcome this issue. Over 100 pressure responses obtained via CPT at the two test sites were examined by means of type curve analysis. The spatially distributed hydraulic parameters were analyzed within the framework of geostatistics. The kriged heterogeneous hydraulic conductivity fields were inputted into a numerical flow and transport model to study, along with other issues, the impact heterogeneity has upon the in-situ leaching process. A number of conclusions were reached based upon the investigation of the two test sites. Comparison between single-hole and cross-hole hydraulic tests revealed the probable presence of a low permeable skin surrounding the wells. By far, the most important hydrologic mechanism controlling the in-situ leaching process in San Manuel was the massively induced hydraulic background gradient, in places, on the order of 35°. Modeling revealed insignificant differences on the sweeping efficiency of the formation between heterogeneous and homogeneous simulations. However, due to the twodimensional nature of the collected data, additional three-dimensional information may lead to a different conclusion.

Complete issue of 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

Complete issue of the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona