Rising Water and Nitrate Levels within an Alluvial Aquifer near Phoenix, Arizona

by Karol Wolf,

Document Type: Proceeding Paper

Part of: WRPMD'99: Preparing for the 21st Century


(No paper) An analysis of water level data from more than a hundred water supply wells show that water levels have been rising at a considerable rate since 1980 in some portions of the East Salt River Valley basin near Phoenix, Arizona. This rise is associated with a reduction in pumpage and continued recharge from irrigation, septic tanks, stockyards, and Salt River flows over this sametime period. Historical water quality data show that nitrate levels have also risen throughout most of the study area. Groundwater nitrate concentrations are considerably higher beneath irrigated agricultural areas than beneath non-agricultural lands. The highest levels of groundwater nitrate occur in areas that have relatively high density of stockyards and septic tanks. Nitrogen isotope data collected on select wells correlate well with prior and current land use. In some regions, the high nitrate levels in the deep percolation water from these sources and the rising water table caused by it may be a contributing factor to the increase in groundwater nitrate levels as pumped from wells. If the rate of water level rise continues, the potential exists for water logging problems in the next few decades or so. Finding a use for the nitrate contaminated groundwater will also pose difficult challenges.

Subject Headings: Nitrates | Water level | Water quality | Salt water | Water supply | Water pollution | Groundwater pollution | Arizona | United States | Phoenix

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