Water Quality From Water‐Harvesting Systems

Abstract

AbstractWater harvesting is a technique used to supply animal and domestic drinking water in areas where more conventional methods cannot supply sufficient water. The water collected by a water‐harvesting system has the potential of being contaminated by deterioration by‐products of the materials used in constructing the system, from dust that is deposited on the catchment surface, or from impurities trapped in the rain. During a 3‐y period, runoff water samples were collected for water quality analyses from 10 types of catchment treatments on operational and experimental water‐harvesting systems in Arizona. Atomic absorption spectrophotometry techniques were used to determine the concentrations of Al, As, Cd, Ca, Cr, Co, Cu, Fe, Pb, Mg, Hg, K, Na, V, and Zn in each water sample. There was no evidence that deterioration of the catchment treatments would cause a contamination of the runoff water. With the exception of As, most samples had significantly lower concentrations of these constituents than the maximum standards for animal or domestic drinking water supplies.Arsenic was the only chemical consistently found in the water samples at potentially hazardous concentrations for domestic drinking water supplies. Excessive As concentrations were not associated with any specific type of catchment treatment. The logarithm of As concentration in the runoff was positively correlated with the logarithm of the time since the previous rain, and negatively correlated with the logarithm of the total rainfall quantity. Apparently, As was deposited on the catchment surface as dryfall dust, and/or was washed from the atmosphere by the rainfall.