• Converting Chaparral to Grass to Increase Streamflow

      Ingebo, Paul A.; Rocky Mountain Forest and Range Experiment Station (Arizona-Nevada Academy of Science, 1972-05-06)
      Chaparral covers 4 million acres in Arizona. There is interest in determining how much these lands contribute to surface water supply, and how this contribution could be changed by conversion of chaparral cover to grass or grass forb. Results from treatment in the Whitespar watersheds are interpreted. Live oak and true mountain mahogany dominate the study area, which averages 22.7 inches of annual precipitation. Whitespar B watershed was converted to grasses in 1967, and litter was not disturbed. The 246 acre watershed produced more streamflow than the untreated, 303-acre control which tended to remain intermittent. Prior to treatment, streamflow in both watersheds was quite well synchronized. Watershed b has since had continual flow. Winter flows contribute about 77 percent of the increased streamflow volume. The degree of effect is still under study, but a new rainfall-runoff relationship for the treated watershed is necessitated.
    • Design and Pilot Study of an Arizona Water Information System

      Foster, K. E.; Johnson, J. D.; Office of Arid Land Studies, University of Arizona (Arizona-Nevada Academy of Science, 1972-05-06)
      Water information systems may have different demands, such as responding to queries about rainfall-runoff relationships, water level data, water quality data and water use. Data required for retrieval may need display, such as a hydrograph. Information systems are reviewed and results of specific water information agencies are reported. Agencies in Arizona are listed with their specific water information need. Development of a water activity file and water information system is outlined for Arizona as a pilot project. Linkage of units within the data system is shown, as is the information system's questionnaire to project leaders. Information currently in the system includes water quality from the state department of health for 450 wells in the Tucson basin, and water level, storage, storage coefficient and transmissivity supplied by the Arizona water commission for the Tucson basin and Avra Valley. Quality of data submitted to the system should be reflected in retrieval for better understanding of the data. This consideration is planned for the coming fiscal year.
    • A Proposed Model for Flood Routing in Abstracting Ephemeral Channels

      Lane, Leonard J.; Soil and Water Conservation Research Division, Agricultural Research Service, USDA; Arizona Agricultural Experiment Station, Tucson, Arizona; Southwest Watershed Research Center, Tucson, Arizona 85705 (Arizona-Nevada Academy of Science, 1972-05-06)
      Almost all runoff from semiarid rangeland watersheds in southern Arizona results from intense highly variable thunderstorm rainfall. Abstractions, or transmission losses, are important in diminishing streamflow, supporting riparian vegetation and providing natural groundwater recharge. A flood routing procedure is developed using data from the walnut gulch experimental watershed, where flood movement and transmission losses are represented by a system using storage in the channel reach as a state variable which determines loss rates. Abstractions are computed as a cascade of general components in linear form. Wide variation in the parameters of this linear model with increasing inflow indicates that a linear relation between losses and storage is probably incorrect for ephemeral channels.
    • Significance of Antecedent Soil Moisture to a Semiarid Watershed Rainfall-Runoff Relation

      Chery, D. L., Jr.; Southwest Watershed Research Center, USDA, Agricultural Research Service, Soil and Water Conservation Research Division (Arizona-Nevada Academy of Science, 1972-05-06)
      Numerous reports from the southwest claim that soil moisture prior to rainfall-runoff event has no influence on the resulting flow volumes and peak rates. Runoff occurs from many storms that would not be expected to produce runoff, and an explanation lies in the occurrence of antecedent rains. This hypothesis is tested by dividing runoff events into 2 subsets--one with no rain within the preceding 120 hours, and the other with some rain within the preceding 24 hours--and to test the null hypothesis. The hypothesis was tested with rainfall and runoff data from a 40-acre agricultural research service watershed west of Albuquerque, New Mexico, using the Wilcoxon's rank sum test. Various levels of statistical significance are discussed, and shown graphically, to conclude conclusively that antecedent rainfall influences runoff from a semiarid watershed.