• Application of a Finite-Element Model to Overland Flow and Channel Flow in Arid Lands

      El-Ansary, Amgad S.; Contractor, Dinshaw N.; Civil Engineering Department, University of Arizona, Tucson, AZ 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
      A mathematical model to simulate overland and channel flow using the finite element technique was adapted and applied to a small semi-arid rangeland watershed (2,035 acres) in the USDA Walnut Gulch experimental watershed in the Southwestern United States. The Holtan equation was used to estimate precipitation excess, and with the precipitation excess as input, the finite-element technique was used to route overland and channel flow. The program was structured with sufficient flexibility so that effect of land use changes either gradual or sudden, on runoff hydrograph could be estimated. Abstraction losses in the stream channel are accounted for. The simulation model predictions are compared with field data for several storms and the comparisons are satisfactory; however, improvements could be made with additional data on antecedent moisture content and better estimates of abstraction losses. Based on these comparisons, it is felt that the model can be used to estimate runoff hydrographs from ungaged watersheds in semi-arid regions.
    • The Biodynamic Treatment of Wastewater

      Buras, Netty; Department of Civil Engineering, University of Arizona, Tucson, AZ 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
      A wastewater treatment is proposed. It is based on: 1. The assumption that the changes taking place during the transformation of wastewater into effluent are unidirectional processes, entailing a number of well- defined sequential stages, and 2. The knowledge that the aerobic bacterial populations present in wastewater are able to decompose efficiently the organic matter in the wastewater, given optimal conditions for their development. Preliminary experiments in which these assumptions have been tested showed the production of a high quality effluent, as measured by the conventional chemical, physical and public health standards. No pathogenic bacteria or human enteric viruses have been recovered from the effluent so produced. A comparison between the processes of the "conventional biological" and a "biodynamic" treatment will be presented.
    • Costs and Returns to Irrigation Under the Central Arizona Project: Alternative Futures for Agriculture

      Bush, David B.; Martin, William E.; Department of Agricultural Economics, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
    • Designing Water Rate Structures to Promote Conservation

      Woodard, Gary C.; Division of Economic and Business Research, University of Arizona, Tucson, AZ 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
      A growing number of water providers are implementing rate structures intended to promote water conservation. The impact of an increasing block rate structure on residential water demand is examined for Tucson, Arizona. Time - series regressions on demand suggest that Tucson Water customers base consumption decisions on the previous month's average price rather than the marginal price of water. This behavior, coupled with a substantial monthly service charge, results in the rate structure discouraging, rather than encouraging, conservation. An alternate pricing structure based on distinguishing indoor and outdoor water uses is presented. Issues of economic efficiency and social equity are considered.
    • Effect of Storage Temperature on Survival of Coliforms in Ground Water

      Kutz, S. M.; Sinclair, N. A.; Department of Microbiology and Immunology, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
    • Effect of Stream Discharge on Phosphorus Loading and Assimilation in the East Verde River

      Athey, Patrick V.; Sommerfeld, Milton R.; Department of Botany and Microbiology, Arizona State University, Tempe, AZ 85287 (Arizona-Nevada Academy of Science, 1984-04-07)
    • Effects of Mixed Conifer Forest Openings on Snow

      Plasencia, Douglas J.; Ffolliott, Peter F.; Gottfried, Gerald J.; School of Renewable Natural Resources, University of Arizona, Tucson, Arizona 85721; Rocky Mountain Forest and Range Experiment Station, Flagstaff, Arizona 86001 (Arizona-Nevada Academy of Science, 1984-04-07)
    • Evaluation of Nitrate in Groundwater South of Tucson, Arizona

      Postillion, Frank G.; Pima Association of Governments, Tucson, AZ (Arizona-Nevada Academy of Science, 1984-04-07)
      Levels of nitrates in excess of the US EPA standard of 45 mg/l were found in well water south of Tucson, Arizona. Most groundwater in this area with high nitrate content is beneath lands presently or formerly irrigated. The highest nitrate contents are present in the upper several hundred feet of the aquifer suggesting a source at the land surface. Nitrate contents in water from most wells in the study area were less than 7 mg/l in the late 1940's, but by the mid-1960's the nitrate level exceeded 25 mg/l in most wells. In the summer of 1982, more than 12 wells exhibited water with a nitrate content exceeding 45 mg/l. Analytical techniques included assessment of pollution sources at the land surface, chemical indicators such as chlorides, nitrogen and oxygen isotopes, and evaluation of the hydrogeologic conditions in the study area. Sources of nitrate contamination included sewage effluent disposal into the Santa Cruz River, historical irrigation practices, septic tank area, and an abandoned hog farm.
    • The Growth and Survival of "Naturally-Occurring" Bacteria in Well Water

      Stetzenbach, L. D.; Yates, M. V.; Gerba, Charles P.; Sinclair, N. A.; Department of Microbiology and Immunology, University of Arizona, Tucson, Arizona (Arizona-Nevada Academy of Science, 1984-04-07)
      Ground water is an increasingly significant source of potable water that has traditionally been considered safe for human consumption without treatment. Although routinely monitored for the presence of coliforms, information concerning the non-coliform bacteria present in well water has been largely ignored. The purpose of this study was to demonstrate the ability of non-coliform, "naturally-occurring" bacteria to increase in number and persist in unamended well water. Water was collected from 19 continuously pumping wells throughout the Tucson basin and stored at in situ well water temperatures. Bacteria were enumerated using epifluorescent microscopy at predetermined intervals over a 30-day period. Greater than 3 log increases in bacterial numbers were noted after 24 hours of incubation. Maximum numbers were achieved after 3 days followed by a gradual decline ranging from 0.39-1.84 logs. Non-coliform, opportunistic pathogens have been isolated from Tucson well water. Their increase in number and survival in well water may impact the quality of untreated drinking water.
    • Hydrogeology of the Camp Verde Area, Central Arizona

      Glotfelty, Marvin; Northern Arizona University, Flagstaff, Arizona (Arizona-Nevada Academy of Science, 1984-04-07)
      The area of study covers 26.5 square miles ranging from the confluence of Beaver Creek and Verde River to the north, to the confluence of West Clear Creek and the Verde River to the south. Ground water depths for 471 domestic and agricultural wells were obtained, and selected wells were field checked to insure accuracy of data. A ground water contour map was constructed from well data at a 1:24,000 scale with a 20 foot contour interval. Aquifer characteristics of the study area were obtained via pump test data. Aquifer characteristics were then plugged into a USGS 2-D computer model, which has been modified to give the best representation of the Verde aquifer. The 2-D computer program and the 1:24,000 ground water map will be useful predictive tools to prevent overdraft and poor well spacing as development of the study area leads to greater withdrawal demands.
    • Impact of Urban Conservation on Groundwater Pumping and Projected Effluent Flow in the Tucson Area

      Foster, Kennith E.; Brittain, Richard G.; DeCook, K. James; Office of Arid Lands Studies; College of Architecture; Cooperative Extension Services (Arizona-Nevada Academy of Science, 1984-04-07)
    • Implementation of Isotope Subroutine to Computer Program PHREEQE and their Application to C-14 Ground Water Dating

      Cheng, Song-Lin; Long, Austin; Laboratory of Isotope Geochemistry, Department of Geosciences, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
      The age of ground water is defined as the length of time the water has been isolated from the atmosphere. Among the methods for ground water dating, C14 is the most commonly used and the most intensively studied tool. The concentration of C14 in dissolved inorganic carbon can change as a result of chemical processes in nature, hence, an adjustment factor Q is included in the age equation. A = QAo(e^(- λt)) Various models have been proposed to account for this adjustment factor. Among those models, the mass transferbalance approach is the most rigorous method. Wigley, Plummer, and Pearson (1978) formulated a mass balance equation to calculate the evolution of C13 and C14 in natural water systems closed to soil CO2 gas. Deines, Langmuir, and Harmon (1974) used a set of dual chemical-isotopic equilibrium equations to calculate changes of C13 in systems open to soil CO2 gas. This study implements these two models as a subroutine and adds carbon isotope mixing equations to PHREEQE (Parkhurst, Thorstenson, and Plummer, 1980), which is a computer program for general hydrogeochemical calculations. With this program package, it is now possible to simulate the evolution of chemical and carbon isotopic compositions, including C14, of ground water from open to closed systems. These simulations allow much improved inferences of Q factors for radiocarbon groundwater dating.
    • Microbial Contamination of Groundwater in the Pinetop-Lakeside Area of Northern Arizona

      Mohrbacher, Carl; De Leon, Ricardo; Toranzos, Gary A.; Mullinax, Rebecca L.; Gerba, Charles P.; University of Arizona, Tucson, Arizona (Arizona-Nevada Academy of Science, 1984-04-07)
      The Pinetop-Lakeside area located in southeastern Navajo County, Arizona, has experienced several outbreaks of probable waterborne gastroenteritis. The many on -lot sewage disposal systems, thin soils and fractured crystalline rock aquifers make this area especially vulnerable to biological degradation of the groundwater supply. This study was designed to assess the extent of bacteriological and virological contamination of groundwater and relationships between indicatior bacteria, coliphages and human pathogenic viruses. Twenty different wells were selected and monitored for conforms, fecal conforms, fecal streptococci, coliphages, enteric viruses, and various physical and chemical properties of the water. Extensive microbial contamination of the groundwater was observed, which increased dramatically after a period of heavy rainfall. Almost 90% of all well samples contained coiform levels in excess of drinking water standards.
    • A Modified Cover Parameter Value for the Universal Soil Loss Equation

      Jemison, Roy L.; School of Renewable Natural Resources, University of Arizona, Tucson, Arizona (Arizona-Nevada Academy of Science, 1984-04-07)
      The Universal Soil Loss Equation (USLE) was formulated for estimating soil loss from agricultural lands in the eastern United States. It has also proven to be useful in assisting land managers make better decisions for other land uses. Studies have shown that when the equation is used in areas other than where it was developed, predictions may be inadequate due to variations in estimates of the environmental parameters used in the equation. Ten years of rainfall, runoff, and sediment yield data collected by the USDA /Agricultural Research Service were used to evaluate several cover parameter values (C) presently in use in the Southwest. Preliminary analysis of data showed no statistical differences between calculated and measured cover parameter values.
    • A Novel Method of Evaporation Suppression in a Water Harvesting System

      Karpiscak, Martin M.; Foster, Kennith E.; Rawles, R. Leslie; Office of Arid Lands Studies, College of Agriculture, University of Arizona, Tucson, Arizona 85719 (Arizona-Nevada Academy of Science, 1984-04-07)
      A demonstration agrisystem located in an area receiving less than 250 mm rainfall annually has been constructed through a cooperative program between the City of Tucson and the University of Arizona. Mondell pine, aleppo pine, jojoba, grapes, eucalyptus, olives, and other crops were cultivated in a 4 ha NaC1 treated catchment system designed to concentrate rainfall on plants and channel excess water into a system of storage reservoirs. Evaporation was reduced from an 80 foot diameter above ground reservoir by means of 225,000 plastic film cans, at a cost of approximately 50 cents /ft². Data acquired from evaporation pans indicates a 50 to 70 percent reduction in evaporation of the stored water. Additionally, this research has provided data that 1) demonstrates the economic potential for agriculture of currently retired farmland, 2) investigates the feasibility of applying water harvesting method for agricultgural purposes in a semiarid region, and 3) evaluates water harvesting as an alternative to meet the ever increasing demand for water.
    • Occurrence of Enteroviruses in Recreational Areas of Oak Creek, Arizona

      Sing, Shri N.; Rose, Joan B.; Williams, Jerry R.; Heinl, Rhonda M.; Gerba, Charles P.; University of Arizona, Tucson, AZ 85721; Arizona Department of Health Laboratory Services, Phoenix, AZ (Arizona-Nevada Academy of Science, 1984-04-07)
      No previous studies have been conducted in the United States on the occurrence of human pathogenic enteric viruses in freshwater recreation areas. Recent epidemiological studies have shown a significant amount of gastroenteritis associated with swimming in recreational waters meeting current bacteriological standards. Evidence also suggests that the observed gastroenteritis has a viral etiology. This study was designed to determine the occurrence of enteroviruses in a heavily used recreational area during the summers of 1982 and 1983. Positively charged Zeta-plus filters were used for collection of virus samples which ranged in size from 67 to 210 gallons. Enteroviruses, including poliovirus type 1, were isolated from several samples. Coliforms and fecal coliform standards for recreational use were exceeded in several samples. It is possible that the presence of enteric viruses in this popular recreational area may be a source of enteric viral disease during the summer months.
    • Questions Raised by the Tucson Flood of 1983

      Baker, Victor R.; Department of Geosciences, University of Arizona, Tucson, Arizona 85721 (Arizona-Nevada Academy of Science, 1984-04-07)
      Post-disaster studies of the October 1983 flood lead to serious questions concerning the applicability to southern Arizona of nationally standardized procedures for flood hazard evaluation. When the U.S. Water Resources Council method of determining flood flow frequency is applied to the Santa Cruz River annual peak flow record at Tucson for the period 1915-1982, the 1983 flood discharge is predicted to have an exceedence probability of less than 0.001. Hydro-climatological considerations suggest that such large floods occur much more frequently. The standard procedure for flood hazard zonation utilizes step-backwater calculations for the extant channel and valley floor geometry to route the discharges obtained from the standard flood flow frequency analysis. This procedure, as used in the Federal Emergency Management Agency flood insurance study, greatly overestimated the areas of overbank flooding along the Santa Cruz River as experienced in the 1983 flood. A detailed post-flood study was performed to assess channel change for reaches of Pantano Wash, Tanque Verde Creek, the Rillito, and the Santa Cruz River in the Tucson Basin. Bank erosion occurred as cutbank recession of actively migrating meander bends except where local areas of bank were preserved by revetments. Where revetments remained intact during the flooding they served to concentrate and enhance bank erosion in the unprotected reaches immediately downstream. From an overall river management perspective, piecemeal bank protection generates greater channel instability than does no protection at all.
    • Recent Changes in a Flood Series

      Reich, Brian M.; Engineering Division, City of Tucson, Arizona (Arizona-Nevada Academy of Science, 1984-04-07)
    • Reclamation of Wastewater for Open Access Irrigation

      Hager, Donald G.; Rubel and Hager, Inc., Tucson, Arizona (Arizona-Nevada Academy of Science, 1984-04-07)