• Runoff Estimates for Thunderstorm Rainfall on Small Rangeland Watersheds

      Simanton, J. R.; Osborn, H. B.; USDA-ARS, Southwest Rangeland Watershed Research Center, Tucson, AZ 85705 (Arizona-Nevada Academy of Science, 1983-04-16)
      Almost all runoff from small rangeland watersheds in the Southwest is the result of intense thunderstorm rainfall, and the variability of this rainfall is an important runoff-influencing factor in such areas where high intensity rainfall dominates watershed hydrology. Thunderstorm runoff estimates for small rangeland watersheds can be made using a multitude of estimating techniques ranging from simple table and graph procedures to utilizing high-speed computers, and even the most sophisticated models greatly simplify the rainfall input. In this paper, the combined effects of rainfall quantity and intensity, and the rainfall energy factor, EI, in the Universal Soil Loss Equation (USLE), were analyzed, and simple procedures for estimating semiarid rangeland runoff volumes were developed. Equally good correlations with runoff volumes were found for EI, and for total storm rainfall times maximum rainfall intensities for 5, 10, and 30 minutes and the square of the maximum 60-minute rainfall.
    • Stable Isotopes and Ground-Water Chemistry as Indicators of Mountain Front Recharge, Tucson Basin, Pima County, Arizona

      Mohrbacher, Carl; University of Arizona, Tucson, Arizona (Arizona-Nevada Academy of Science, 1983-04-16)
      The relative importance of mountain front recharge as compared to total recharge was determined for a portion of the Tucson basin aquifer margin by interpretation of chemical and isotopic data. Concentrations of 180/160 lower than 6 -10.7 ⁰/00 as compared with a background of about 6 -9.3 ⁰/00 in ground water from the base of the mountains in the gneissic rock suggest the presence of recharge from significantly higher elevations. The trilinear diagram of major ions dissolved in ground water from 123 wells in the Santa Catalina foothills indicates three water types. Water from wells in gneissic rock is high in sodium and potassium content and low in calcium and magnesium. Wells in the gypsiferous Pantano Formation yield water high in sulfates. The majority of wells in the study area, which are along major streams and in the regional aquifer, have calcium carbonate type water. Their chemistry indicates only minor contributions from the gneissic mountain block and the underlying Pantano Formation. Funding for this project came from the Spanish Project Register T377017.
    • Stock Tank Characteristics and Performance in the Beaver Creek Watershed, North-Central Arizona

      Hughbanks, Julia; Northern Arizona University, Flagstaff, Arizona (Arizona-Nevada Academy of Science, 1983-04-16)
      The Beaver Creek Watershed is located in southern Coconino and southeastern Yavapai Counties, Arizona. This 472 square mile watershed contributes to Beaver Creek which flows into the Verde River. The objectives of this study were: 1) to monitor a network of stock tanks in the watershed on a bi-weekly basis to document seasonal fluctuations in water levels over one year; 2) to investigate the impact of stock tanks on local hydrology by determining the number of times the tanks fill during one year; and 3) to determine a set of dependent variables which would quantify stock tank performance, and a set of independent variables representing characteristics of the tanks and their drainage basins which could affect the performance of the tanks. The relative importance of each of these independent variables in influencing tank performance was then determined through statistical analysis.
    • Subsurface Production of Chlorine-36 and Its Impact on Ground Water Dating

      Kuhn, Mark W.; Davis, Stanley N.; Zito, Richard; Bentley, Harold W.; University of Arizona, Tucson, Arizona (Arizona-Nevada Academy of Science, 1983-04-16)
      Chlorine-36 is an important radioisotope with which to date old ground water. The initial chlorine-36 in ground water originates in the atmosphere by cosmic ray spallation of argon-40. Following precipitation and infiltration processes, the natural decay of this radioisotope is then used to date ground water. One must consider, however, the production of chlorine-36 in the subsurface. The production reaction of most interest is ³⁵C1 + neutron → ³⁶C1 + gamma. Buildup of chlorine-36 in the subsurface can result from cosmic ray secondary neutrons near the surface and natural radioactivity produced neutrons below the surface. These production mechanisms, if not taken into consideration, will contribute to the error in chlorine-36 age determinations. To predict subsurface production rates, field measurements were made of thermal neutron fluxes for various geologic materials and depths below the surface. Thermal neutron fluxes were found to vary by more than three orders of magnitude. Theoretical calculations of neutron flux were compared to filed measurements. Estimates of chlorine-36 production rates were then calculated and compared to measured values of chlorine-36 in very old ground water, where decay rates have been hypothesized to be equal to production rates.
    • Time-Space Effects of Openings in Arizona Forests on Snowpacks

      Ffolliott, Peter F.; School of Renewable Natural Resources, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1983-04-16)
      Forest openings affect a snowpack during both accumulation and melt phases. At any point in time, a snowpack is the integrated result of all accumulation, redistribution, and melt processes that have taken place before the time of measurement. Since snowpacks do not always have distinct accumulation and melt phases, it is difficult to determine the effect that an opening will have on a snowpack regime. This paper describes an analysis of the effects of openings in Arizona ponderosa pine forests on snowpacks in and adjacent to the openings, using readily available input variables.
    • Tucson's Needs for Central Arizona Project Storage

      Davis, Steven E.; Tucson Water, Tucson, Arizona 85726 (Arizona-Nevada Academy of Science, 1983-04-16)
      The future acceptance and utilization of Central Arizona Project water by the City of Tucson Water Utility present many complex technical, economic, institutional, and environmental problems. Since Congressional adoption of the Colorado River Basin Project Act in 1968, Tucson Water engineers have supported the concept of a large CAP raw water storage reservoir near Cat Mountain west of the City. The United States Bureau of Reclamation, in its Stage Two planning for Phase B of the Tucson Aqueduct, has identified four potential storage sites, including the Cat Mountain location, for economic and environmental evaluation in conjunction with two basic aqueduct alignments. Engineers of the municipal water utility have utilized available computer tools to develop a preferred CAP delivery location and elevation economically advantageous to water rate payers. This paper discusses the various factors associated with Tucson's projected need for CAP water storage including reliability, operational flexibility, water quality, shortage, and power management. Each of these factors will affect the degree to which the water utility can successfully assimilate Central Arizona Project water into its groundwater supply system. Although a decision regarding storage location and volume has been postponed for the present, the initial years of CAP usage by the City of Tucson will provide sufficient test to justify the decision for no storage or prove its necessity.
    • Virus Fate in Groundwater

      Gerba, Charles P.; Departments of Microbiology, and Nutrition and Food Sciences, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1983-04-16)
    • Virus Survival in Groundwater

      Yates, M. V.; Gerba, C. P.; Department of Microbiology, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1983-04-16)
    • Volatile Organic Ground Water Contamination in the Tucson Airport Super Fund Area, Tucson, Arizona

      Eberhardt, Sandra; Beilke, Pamela; Angell, James; Arizona Department of Health Services (Arizona-Nevada Academy of Science, 1983-04-16)
      The Tucson Airport Super Fund Area is currently being investigated by the Environmental Protection Agency, the Arizona Dept. of Health Services, the City of Tucson and the Arizona Dept. of Water Resources for volatile organics and heavy metal ground water contamination. The volatile organics include trichloroethylene (TCE), trichloroethane (TCA), dichloroethylene (DCE) and heavy metals, primarily chromium. The area is defined as north of Los Reales Rd. to distinguish this contamination from the US Air Force Plant No. 44 contamination south of Los Reales Rd. The investigation includes defining the hydrogeology, the extent of ground water contamination and potential contamination sources. The aquifer being contaminated is located in the Upper Santa Cruz Basin and is the principal source of domestic water for the City of Tucson. The area of concern currently contains 177 water wells; 24 of these wells are contaminated with TCE concentrations ranging from 5 ug /1 to greater than 400 ug /l. This includes 6 City of Tucson public supply wells. There are currently 6 potential contamination sources being investigated. The first phase of Super Fund will enable the State and City governments to collect and analyze data which will be used for remedial action.
    • Water Balance Calculations, Water Use Efficiency, and Aboveground Net Production

      Lane, L. J.; Stone, J. J.; USDA-ARS, Tucson, Arizona 85705 (Arizona-Nevada Academy of Science, 1983-04-16)
      A discrete form of the water balance equation is used to illustrate the interaction among precipitation, runoff, percolation below the root zone, bare soil evaporation, plant transpiration, and plant available soil moisture. Under rangeland conditions, water availability is often the limiting factor in plant survival and growth. Therefore, the water balance equation is used, together with soils data and water use efficiency factors, to estimate annual aboveground net primary production of perennial vegetation.
    • Water Harvesting: An Alternative Use for Retired Farmlands

      Karpiscak, Martin M.; Foster, Kennith E.; Rawles, Leslie R.; Office of Arid Lands Studies, College of Agriculture, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1983-04-16)