• Salinity Control Planning in the Colorado River System (invited)

      Maletic, John T.; Water Quality Office, Engineering and Research Center, Bureau of Reclamation, Denver, Colorado (Arizona-Nevada Academy of Science, 1974-04-20)
      In the lower reaches of the Colorado River, damages from the increase in salinity to U.S. water users are now estimated to be about 53 million dollars per year and will increase to about 124 million dollars per year by the year 2000 if no salinity control measures are taken. Physical, legal, economic, and institutional aspects of the salinity problem and proposed actions to mesh salinity control with a total water management plan for the basin are discussed. A scheme is presented for planning under the Colorado River water quality improvement program. Recent legislative action is also discussed which provides control plans to improve the water quality delivered to Mexico as well as upper basin water users. These efforts now under study will assure the continued, full utility of Colorado River water to U.S. users and Mexico. However, more extensive development of the basin's natural resources puts new emphasis on total resources management through improved water and land use planning to conserve a most precious western resource - water.
    • A Rational Water Policy for Desert Cities

      Matlock, W. G.; Agricultural Engineering, Soils, Water and Engineering Department, University of Arizona (Arizona-Nevada Academy of Science, 1974-04-20)
      Four sources of water supply for desert cities are rainfall, runoff, groundwater, and imported water, and the potential use for each varies. The government can institute various policy changes to eliminate or reduce the imbalance between water supply and demand. Restrictions should be placed on water-use luxuries such as swimming pools, subdivision lakes, fountains, etc. Water pricing should be progressive; each unit of increased use above a reasonable minimum should be charged for at an increasing rate. Runoff from individual properties, homes, storage, and supermarkets should be minimized through the use of onsite recharge wells, and various collection methods should be initiated. A campaign to acquaint the general public with a new water policy must be inaugurated.
    • Metropolitan Operated District for Sewage Effluent - Irrigation Water Exchange

      Cluff, C. Brent; DeCook, K. James; Water Resources Research Center, The University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1974-04-20)
      A plan for the reuse of sewage effluent is proposed for the city of Tucson, Arizona. Several kinds of use would be possible, but utilization for irrigation of existing farmland in the Avra-Marana area seems particularly attractive for several reasons: (1) conveyance can be accomplished by gravity flow, (2) no tertiary treatment is required for the presently grown crops, (3) the nutrients in the effluent would be better used, and (4) effluent use would reduce the pumpage of high quality groundwater, conserving it for municipal or other uses. An exchange of wastewater for groundwater for use in the city system is seen as a good alternative to the present practice of the city purchasing farmland in Avra valley in order to acquire the groundwater for conveyance to the Tucson basin. Objectives to maximize the quantity and efficiency of wastewater use may not appear compatible with the profit maximization motive of the individual farmer, and suitable provisions will have to be written into wastewater sales agreements to assure coordination between user and supplier.
    • United States-Mexico Water Agreements and Related Water Use in Mexicali Valley: A Summary

      DeCook, K. J.; Water Resources Research Center, The University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1974-04-20)
      A summary is given of interrelated, technical and institutional events concerning the Colorado River which took place between the United States and Mexico from 1849 to 1974 with emphasis on the 1961-1974 period. Until the treaty of 1944, Mexico had had no guarantee of a specific annual quantity of water, but in the years after 1945, when a guarantee of 1.5 million acre-feet per year was established, more than that amount was available for use. Salinity problems arose, and in 1965 an agreement for a 5-year plan for alleviating the technical and political difficulties surrounding the salinity question was made. In 1973 it was agreed that the United States would build, within approximately 5 years, a facility for desalting the saline drainage water entering Mexico. Fulfillment of the technical provisions for this agreement requires, in any event, the timely provision of federal funds to construct and operate the physical works. The several states should receive assurance that their rights and those of their respective water users will not be impaired within the legal operation of the agreement.
    • Economic Alternatives in Solving the U. S.-Mexico Colorado River Water Salinity Problem (invited)

      Martin, William E.; Arizona Agricultural Experiment Station, the University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1974-04-20)
      A proposed desalting plant is an engineering solution to the effects of a problem which could have been avoided and even now could be reduced on the farm. Water costing $125 per acre-foot will be delivered to Mexico to grow wheat, cotton, garden crops, alfalfa and safflower, of which the average value added per acre-foot was estimated at $80 for cotton and garden crops and $14 for wheat, alfalfa and safflower. The U.S. government, instead of building the desalting complex, could accomplish its purpose just as well by paying each farmer in the Yuma area, in return for the farmers reducing their drainage flow by whatever method they see fit, $114 per acre per year for the next 50 years. With proper management on the farm, the costs of managing salinity need not be high.
    • Laboratory Evaluation of Water-Repellent Soils for Water Harvesting

      Fink, Dwayne H.; U. S. Water Conservation Laboratory (Arizona-Nevada Academy of Science, 1974-04-20)
      Reported are laboratory evaluations to screen water-repellent materials and treatments before testing them in the field. Water repellency tests were conducted on paraffin wax, a wax emulsion and silicon, lard, and a liquid dust suppressant. Six water repellency tests showed that the high rates of paraffin wax and all rates of the dust suppressant produced highly water-repellent soil surfaces. The six water repellency tests were: (1) the aqueous-alcohol drop test for determination of the 90 degree surface tension for a porous solid, (2) the water drop penetration time test, (3) the relative height of a large sessile water drop resting on the smoothed, treated soil surface, (4) and (5) the presence and persistence of air bubbles trapped between the soil-water interface, and test (6) was made to note whether the large sessile water drop from test (3) would infiltrate the soil or evaporate. Tests (3), (4), and (5) proved the most useful of the six methods for measuring water repellency. Soil type had no significant influence on degree of water repellency as measured in the laboratory by these six tests.
    • Assessing Soil-Water Status Via Albedo Measurement

      Idso, Sherwood B.; Reginato, Robert J.; ARS, USDA, U. S. Water Conservation Laboratory, Phoenix, Arizona 85040 (Arizona-Nevada Academy of Science, 1974-04-20)
      Reliable information on soil-water status is required in order to make accurate water balance studies of watersheds, to determine the survival probabilities of various types of vegetation between rainfalls in low rainfall areas, and to determine the susceptibility of the uppermost soil to wind erosion. Simple solarimeters may help to accomplish this objective. Bare soil albedo was a linear function of the water content of a very thin surface layer of soil, and albedo correlated well with water contents of thicker soil layers. In addition, albedo measurements could be used to delineate the 3 classical stages of soil drying. Albedo may also be used to differentiate between the initial potential rate phase of evaporation following an application of water, and the succeeding falling rate phase. Results of applying this technique to a field of Avondale clay loam indicate that 20% to 25% of the water applied by either irrigation or rain will be lost by stage 1 potential evaporation, independent of seasonal variations in evaporative demand. Presently the techniques developed are applicable only to bare soil surfaces.
    • Increasing Forage Production on a Semiarid Rangeland Watershed

      Tromble, J. M.; United States Department of Agriculture, Agricultural Research Service, Western Region, Southwest Watershed Research Center, Tucson, Arizona 85705 (Arizona-Nevada Academy of Science, 1974-04-20)
      Two native grass species, blue grama and sidecoats, were successfully seeded on a semiarid rangeland on the walnut gulch experimental watershed in southeastern Arizona. Optimum seeding dates selected were those within the time period most likely to receive precipitation, and grass stands were established in two successive years with average rainfall. Shrubs were killed by root-plowing at a depth of 14 inches, a procedure which was more than 95% successful in controlling sprouting shrubs. Forage production measurements taken on nm-28 sideoats and Vaughn sideoats showed a yield of 1,950 and 2,643 pounds of forage per acre, respectively, for the 2 years following the seeding, whereas untreated sites produced 23 and 25 pounds per acre of forage. Results indicate that success in establishing a stand of native grass is increased through use of existing hydrologic data.
    • Applicability of the Universal Soil Loss Equation to Semiarid Rangeland Conditions in the Southwest

      Renard, K. G.; Simanton, J. R.; Osborn, H. B.; United States Department of Agriculture, Agricultural Research Service, Western Region, Southwest Watershed Research Center, Tucson, Arizona 85705 (Arizona-Nevada Academy of Science, 1974-04-20)
      An erosion prediction method that has recently received wide attention in the United States is the universal soil loss equation which is given as: a=rklscp. Where a = estimated soil loss (tons/acre/year), r = a rainfall factor, k = a soil erodibility factor, l = a slope length factor, s = a slope gradient factor, c = a cropping-management factor, and p = an erosion control practice factor. Data collected on the walnut gulch experimental watershed in southeastern Arizona were used to estimate these factors for semiarid rangeland conditions. The equation was then tested with data from watersheds of 108 and 372 acres. The predicted value of annual sediment yield was 1.29 tons/acre/year as compared with an average 1.64 tons/acre/year for 4 years of data for the 108-acre watershed, and a sediment yield of 0.39 tons/acre/year was predicted for the 372-acre watershed as compared with the measured value of 0.52 tons/acre/year. Although good agreement was noted between predicted and actual sediment yield, additional work is needed before the equation can be applied to other areas of the southwest.
    • A Technique to Evaluate Snowpack Profiles in and Adjacent to Forest Openings

      Ffolliott, Peter F.; Thorud, David B.; Department of Watershed Management, University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1974-04-20)
      Profiles of snowpack build-up in openings in forest overstories have been widely observed; however, a quantitative characterization of such a snowpack profile would aid in developing empirical guidelines for improving water yields from snowpacks. A technique is outlined that illustrates (a) evaluating snowpack profiles in and adjacent to individual forest openings in terms of increase or decrease in water equivalent, and (b) defining trade-offs between the estimated increase or decrease in snowpack water equivalent and the forest resource removed. Snowpack water equivalent during peak seasonal accumulation was measured in and adjacent to a clearcut strip in a ponderosa pine stand in north-central Arizona. A 4-degree polynomial, which defines the snowpack profile in terms of deposition, redistribution, and ablation characteristics, was empirically selected to describe snowpack water equivalent data points. An increase of 60 percent in snowpack water equivalent was realized by removing 46 percent of the ponderosa pine in the zone of influence, using a strip equal to one and one-half the height of the adjacent overstory.
    • Water Resources Research on Forest and Rangelands in Arizona (invited)

      Hibbert, Alden R. (Arizona-Nevada Academy of Science, 1974-04-20)
      A progressive and coordinated effort is underway to provide a sound technical basis for managing water resources on forest and rangelands in the Southwest. An in-house Forest Service (USDA) research program including pilot testing and economic evaluations of multiple-use alternatives provides information necessary for this purpose. Demands for other goods and services also are increasing on these lands in the face of a burgeoning population. homeseekers, vacationers, and recreationists seek a variety of recreational. experiences that require open space and a relatively undisturbed environment. Frequently these uses conflict, and the combined pressure from too many activities can damage the environment. A new research effort has been organized in the central and southern Rocky Mountain Region to cope with these problems. Nine Western universities including Northern Arizona University, Arizona State University, and University of Arizona have joined forces with the Rocky Mountain Forest and Range Experiment Station to form the Eisenhower Consortium for Western Environmental Forestry Research. Simply stated, the consortium seeks to better our understanding of the relationships between man and his open-space environment in order that its quality might be maintained.