• Renovating Sewage Effluent by Ground-Water Recharge

      Bouwer, Herman; Lance, J. C.; Rice, R. C.; U.S. Water Conservation Laboratory, Soil and Water Conservation Research Division, Agricultural Research Service, U.S. Department of Agriculture, Phoenix, Arizona 85040 (Arizona-Nevada Academy of Science, 1971-04-23)
      Sewage effluent is commonly used for the irrigation of crops that are not consumed raw. Due to continued population growth in the Salt River Valley, Arizona, economic reuse of municipal waste waters is becoming essential. The salt river bed has about 3 ft of fine loamy sand underlain by sand and gravel layers to great depth and a groundwater table at about 10 ft depth. These conditions are very favorable for high-rate waste water reclamation by groundwater recharge. The activated sludge plant in phoenix will probably be discharging 250 mgd by the year 2000. At 4.5 ft average annual water use, this could irrigate about 70,000 acres, possibly more than agriculture will need at that time. A sewage effluent renovation pilot project was located about 1.5 miles from the plant. It contains 6 parallel recharge basins 20 to 700 ft each, spaced 20 ft apart. The basins were covered by grass, gravel or were left bare. Observation wells were installed at various locations in the area. Results indicated that infiltration rates were fastest in the grassy basins. Phosphate, nitrogen and median fecal coliform levels were all lower after this form of tertiary treatment. Practical details of the application of this water reclamation method in the Salt River Valley are outlined. Costs would be 5 dollars/af, less than 1/10 the equivalent costs of in-plant tertiary treatments.
    • Nitrogen Balance for a 23-Square Mile Minnesota Watershed

      Johnson, Jack D.; Office of Arid Land Studies, University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1971-04-23)
      The nitrogen balance of a watershed near the city of New Prague, Minnesota was evaluated as part of an overall study on lake and stream eutrophication. Although the n-balance of a humid Midwest watershed cannot be expected to be identical to that of an arid watershed, the processes are the same and differences should be mainly quantitive. Sources of input and causes of depletion are reviewed for 4 points in the nitrogen cycle: the atmospheric zone, the soil-atmosphere interface, the plant-root and soil-water zone and the surface water zone. In the New Prague watershed, commercial fertilizer and bulk precipitation were the major sources of input, contributing, respectively, 53% and 34.4% of the total input of 2.34 million lb/yr. Crop yield and soil or groundwater storage contributed 52.1% and 20.4% of non-enrichment depletions. The closeness of the values of crop yield and commercial fertilizer application was an unfortunate coincidence and is certainly not an indication that the entire fertilizer supply was taken up cry crops. In an arid environment, free from fertilized agriculture, bulk precipitation probably provides the major source of nitrogen compounds.
    • Recharging the Ogallala Formation Using Shallow Holes

      Dvoracek, M. J.; Peterson, S. H.; Hydrology & Water Resources, University of Arizona; Agricultural Engineering Department, Texas Tech University (Arizona-Nevada Academy of Science, 1971-04-23)
      The southern bed of the ogallala aquifer is hydrologically isolated from all outside areas of recharge, requiring local precipitation for all natural recharge. Current withdrawals are so much greater than natural recharge that it appears that artificial recharge affords the only means of establishing at least a pseudo-balance. A number of observation wells were drilled at Texas Tech University, and subsequently capped until recharge water became available. The initial recharge was 2.5 af over 12 days, at a rate of 120 gpm for about the first day, after which 60 gpm was relatively constant. Approximately 1 month later, 1.2 af were recharged over 3 days at rates ranging over 140-90 gpm. It became evident that a cavity was present at the bottom of the hole being recharged. On a later recharge occasion, the cavity seemed to have enlarged. During a period of 2 years more than 28 af of surface runoff water have been recharged through the shallow hole with increases in recharge rates for each subsequent recharge period. The nature of this phenomenon and the cavities are not understood. This may represent the long sought after answer to recharge of the aquifer, but much more extensive research needs to be done.
    • Use and Abuse of Southwestern Rivers: Historic Man - The Anglo

      Fireman, Bert; Arizona State University, Tempe, Arizona (Arizona-Nevada Academy of Science, 1971-04-23)
      The exploitation of southwestern rivers is discussed in the context of American intrusion, acquisition and development of Arizona. The first Americans in the region were beaver trappers who quickly decimated the Sonoran beaver but otherwise wrought little environmental impact. Immediately following the acquisition of the region by the U.S. after the Mexican war, gold miners descended upon it from California. They quickly scarred hills and streams, diverting water for placers, building piles of ugly rubble and logging off entire forests. The large numbers of people and towns that followed created a need for more home grown food products and large storage dams were soon built. When these washed out the stored floodwaters did more sharp, tragic damage downstream than even the seasonal floods of the past. The common municipal practice of dumping raw sewage into waterways soon brought water pollution. Following the national reclamation act of 1902, large dams were soon built on major waterways and the multiple use projects came into existence. Today, even the Indians, in their quest for economic betterment are destroying natural waters. They have learned a major lesson from the whites---the rivers they used only for basic needs a century ago, may be more profitable if overused without regard for tomorrow.
    • Field Measurements of Soil-Water Content and Soil-Water Pressure

      Reginato, R. J.; Jackson, R. D.; U.S. Water Conservation Laboratory, Soil and Water Conservation Research Division, Agricultural Research Service, U.S. Department of Agriculture, Phoenix, Arizona 85040 (Arizona-Nevada Academy of Science, 1971-04-23)
      Knowledge of the dynamic water content-pressure potential relationship within the soil profile is useful in determining the importance of hysteresis under natural conditions. Continuous monitoring of water content in the field is now possible using recently developed gamma-ray transmission equipment which allows water content measurements in 1 cm-thick soil layers with an error of 0.0009 gm/gm. The nuclear equipment and the tensiometer assembly for pressure measurements are described. Soil water content and pressure in the top 10 cm of a field soil profile were measured continuously for a 2-week period following an irrigation. The highest water content was measured each day just before sunrise. This declined rapidly from early morning to early afternoon, and was followed by a gain during the mid-afternoon and evening. The amplitude of this diurnal change diminished with time after irrigation. The pressure potential at a depth of 1.5 cm decreased most rapidly as the water content declined, but not exactly in phase. This may have been due to temperature effects on the pressure metering system. A moisture characteristic curve was constructed from the data.
    • Use and Abuse of Southwestern Rivers: The Desert Farmer

      Ayres, J. E.; Arizona State Museum, University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1971-04-23)
      The pre-Columbian Hohokam Indians occupied the major river drainages of central Arizona, and have been the subject of much intense archaeological research. Evidence indicates that the Hohokam began using river water for crop irrigation about 300 B.C., and modified and improved their irrigation systems over time, until the maximum extent of these systems was achieved about 900 a. D. Two types of water control seem to have been utilized: (1) the direct exploitation of rivers through the use of irrigation canals, (2) indirect use through controlled runoff within microdrainages at higher elevations before it reached the rivers. At first, probably only those parcels of land with optimal soils and drainage were used, but apparently population increases fostered by agriculture itself, combined with increasing social and political complexity, necessitated more and more exploitation of marginal lands. Eventually soil problems increased, imposing severe limitations on agriculture. These involved salt and alkali accumulation due to inadequate drainage, soil density and water logging. Additionally, the extension of cropping required the clearing of natural vegetation, which resulted in increased erosion and decreased available native food resources for periods when crops failed. The culture vanished completely about 1450 a. D., probably mainly because of their manner of river exploitation for irrigation. More recent archaeological studies are concentrating not only on river use but also on river abuse.
    • Tree-Ring Dating of Colorado River Driftwood in the Grand Canyon

      Ferguson, C. W.; Laboratory of Tree-Ring Research, The University of Arizona, Tucson, Arizona, 85721 (Arizona-Nevada Academy of Science, 1971-04-23)
      The development of tree-ring chronology for bristlecone pine (Pinus aristata), stretching over 8,200 years, has been used to calibrate the radiocarbon time scale. An extensive deposit of driftwood in Stanton's cave in the grand canyon was estimated to have been deposited on the cave floor about 12,000 years ago on the basis of the 4,095-year radiocarbon age of a split-twig figurine on the surface of the cave floor. However, the initial driftwood specimen gave the surprising C-14 age of 35,000 years. A tree-ring dating study was therefore undertaken on driftwood in the grand canyon in order to: (1) evaluate the driftwood deposit in Stanton's cave; (2) provide a basis for interpreting c-14 dates from canyon archaeological sites; and (3) document a technique for deriving some concept of pre-dam hydrology, especially maximum high water levels. The percentage of dated specimens found indicated that the approach was feasible. A likely interpretation of the seemingly early c-14 dates at archaeological sites is that prehistoric man used old driftwood, as does modern man in the canyon. Tree-ring dates from wood above the pre-dam high water mark indicate that maximum 100-year flood evidence can be obtained.
    • Effects of Fire on Water Infiltration Rates in a Ponderosa Pine Stand

      Zwolinski, Malcolm J.; University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1971-04-23)
      The importance of pine forest as a timber and water producing area has led to intensive management, including protection from wildfire. This has resulted in dense stand growth with increased destructive fire potential and transpirational water loss. In Arizona, as in many areas, prescribed forest burning has been used to effectively reduce these fuel hazards. Some question has arisen about the possible side effects of such treatments, particularly air pollution and reduction of infiltration and water yield. In an effort to determine the effects on infiltration, plots receiving various treatments (control, light burn, heavy burn) were fitted with fusion pyrometers before burning, to measure soil surface temperatures during burning. After burning, infiltrometers were installed. Surface temperatures did not exceed 200 degrees f. For the light burns, and ranged over 350-500 degrees f. During heavy burns. Both heavy and light burns produced highly significant decreases in infiltration capacities after burning and the surface 2 inches showed increases in soil pH, carbon and total nitrogen percentages. Infiltration capacities returned to normal after overwintering and were attributed to frost action on soil texture and porosity. The soil chemical changes decreased slowly over 2 years. Soil water repellency also increased and the significance of this is discussed.
    • Management of Artificial Recharge Wells for Groundwater Quality Control

      Wilson, L. G.; Water Resources Research Center, University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1971-04-23)
      Recharge wells may be used in various problems relating to chemical water quality because of the phenomenon of in-aquifer mixing. This paper reviews specific recharge well-mixing techniques of possible utility in underground mixing operations for nitrate control. Illustrative data from field studies at a recharge site near Tucson, Arizona are presented. Both single- and 2-well types of mixing were investigated. In single-well operations, effluent recharge and pumping of the subsequent mixture occur at the same well. Differences in chlorine ion levels were used to distinguish between recharge effluent and native groundwater. Undiluted effluent was discharged in single-well operations until a pumped volume ratio of about 0.4 was attained. Dilution increased steadily with increased pumping and the relative concentration versus pumped volume curve was s-shaped. Seven-day pauses after effluent recharge resulted in immediate pumping of almost completely diluted water, probably because groundwater movement swept the effluent beyond the pumping unit during the pause. With 2-well pumping, the chlorine breakthrough curve reached a constant level at about 13 days and was close to that of the pause-type, single-well regime.