Quality of Irrigation Water and Surface Return Flows from Selected Agricultural Lands in Nevada During the 1974 Irrigation Season

Abstract

AbstractAgriculture has been identified as a major contributor of pollutants to surface waters. The purpose of this investigation was to gain knowledge of pollutants and pollutant loads carried in surface return flows to receiving waters. Information of this nature is needed by those agencies having administrative responsibility for water quality control. Quantitative and qualitative measurements of irrigation applications (head water) and surface return flows (tail water) were conducted on four sites at three locations in the Carson Valley area of Nevada to investigate the change in pollutant loads of surface waters entering the leaving agricultural units. Dissolved oxygen (DO), biochemical oxygen demand (BOD), total dissolved solids (TDS), NO3‐N, PO4‐P, SO4, and turbidity were considered as major constituents of water quality. Concentrations were combined with flow volumes to compute the constituent loading per irrigation and net infiltrated amounts or seasonal contributions in the surface return flow. Phosphorus and BOD were found to be the major agricultural pollutants contributed by irrigation surface return flows. Net infiltrated amounts of TDS, NO3‐N, and other soluble constituents were recorded. Dissolved oxygen concentrations in head and tail waters were found to be critically low. River standards for DO might be better expressed as a maximum permissible dissolved oxygen deficit (DOd) for water at a given temperature carrying a given amount of BOD. Additional investigations should be undertaken to delineate possible interactions among pollutant constituents. Water quality variations of individual samples should be expressed in statistical terms so that it is possible to identify pollutant interdependencies and to establish an optimized sampling frequency.