Browsing Hydrology and Water Resources in Arizona and the Southwest, Volume 02 (1972) by Subjects
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Effect of a Grass and Soil Filter on Tucson Urban Runoff: A Preliminary EvaluationStorm runoff from the Tucson metropolitan area is unsuitable for most uses without processing. A lysimeter comprised of a grass and soil filter was constructed and is being evaluated as a water-quality treatment facility. The lysimeter is 200 feet long, 4 feet wide and 5 feet deep, and contains homogeneous calcareous loam covered by common grasses. Experimental apparatus was installed to divert less than a cubic foot per second of runoff from urbanized Arcadia Watershed. Runoff flows by gravity over the lysimeter, where surface inflow, surface outflow and subsurface outflow are measured and sampled. Four trials, each associated with a discrete runoff event, were conducted in the fall of 1971. Water samples were analyzed for inorganic chemical constituents, chemical oxygen demand (COD), coliforms, turbidity and sediment contents. Subsurface-outflow samples from initial trials were high in COD and total dissolved solids, representing soil flushing or leaching. Concentrations of inorganics reached a maximum value within a few hours of initial seepage, and then decreased. The peaking represents a salt build-up between trials. Concentrations of COD, coliforms, turbidity and sediment in subsurface-outflow samples decreased significantly during each trial. Surface-outflow samples had lower turbidity, COD, bacteria and sediment contents than surface-inflow samples. Turbidity, suspended and volatile solids, coliforms and COD in runoff samples may be reduced by grass and soil filtration. Increased grass development and soil settling work to produce a better quality effluent. Quantification of the lysimeter's effectiveness will be useful for urban watershed management.
Saline and Organic Water PollutionBetter use and recycling of fresh water, which often recharges the oceans, would reduce man's disruption of nature to increase his supply of potable water. The global distribution of water, desalination, water reclamation and recycling, the roles of soils and plants in recycling and urban misuse of water are discussed. Man can increase his supply of food and good fresh water by recycling and nutrient balance, which imply living off his wastes. Intimate involvement of soils and plants in the production of fresh water and food is clear. Soils and plants should be equally involved in converting our waste water into potable water and useful nutrients. Numerous examples of how this may be done and how it is being done are presented.