Hydrogeology, water chemistry, and transport processes in the zone of contribution of a public-supply well in Albuquerque, New Mexico, 2007-9

Abstract

The U.S. Geological Survey (USGS) is committed to providing the Nation with reliable scientific information that helps to enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information on the Nation's water resources is critical to ensuring longterm availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the availability of that water, measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems. The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, State, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the quality of our Nation's streams and groundwater? How are conditions changing over time? How do natural features and human activities affect the quality of streams and groundwater, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991 to 2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/ studies/study_units.html). National and regional assessments are ongoing in the second decade (2001-12) of the NAWQA Program as 42 of the 51 Study Units are selectively reassessed. These assessments extend the findings in the Study Units by determining water-quality status and trends at sites that have been consistently monitored for more than a decade, and filling critical gaps in characterizing the quality of surface water and groundwater. For example, increased emphasis has been placed on assessing the quality of source water and finished water associated with many of the Nation's largest community water systems. During the second decade, NAWQA is addressing five national priority topics that build an understanding of how natural features and human activities affect water quality, and establish links between sources of contaminants, the transport of those contaminants through the hydrologic system, and the potential effects of contaminants on humans and aquatic ecosystems. Included are studies on the fate of agricultural chemicals, effects of urbanization on stream ecosystems, bioaccumulation of mercury in stream ecosystems, effects of nutrient enrichment on aquatic ecosystems, and transport of contaminants to public-supply wells. In addition, national syntheses of information on pesticides, volatile organic compounds (VOCs), nutrients, trace el...

A Ternary Age‐Mixing Model to Explain Contaminant Occurrence in a Deep Supply Well

“…Wells with broad age distributions can contain contaminants that are associated with one or more fractions of the age distribution. For example, in the alluvial aquifer of the Middle Rio Grande Basin (MRGB), New Mexico, volatile organic compounds (VOCs) are commonly associated with recently recharged young groundwater, whereas elevated arsenic is commonly found in deep, very old groundwater (more than 18,000 years; Bexfield and Plummer ; Plummer et al ; Bexfield et al ). PSWs within the basin near the city of Albuquerque sometimes produce water with arsenic concentrations above the USEPA maximum contaminant level (MCL) of 10 µg/L (effective in 2006).…”

“…Recently, the U.S. Geological Survey National Water‐Quality Assessment (NAWQA) program's TANC topical study (Eberts et al ) investigated the vulnerability of a public‐supply well in Albuquerque, New Mexico (Bexfield et al ). That study used concentrations of 3 H, chlorofluorocarbon‐113 (CFC‐113), and 14 C to develop binary mixing models between young and old components of groundwater for PSWs in the study area.…”

“…That study used concentrations of 3 H, chlorofluorocarbon‐113 (CFC‐113), and 14 C to develop binary mixing models between young and old components of groundwater for PSWs in the study area. Bexfield et al () showed that groundwater at intermediate depths (27 to 80 m below the water table) near a PSW contained as much as 45% young groundwater (recharged since about 1950) and trichloroethylene (TCE) at concentrations greater than 2 µg/L even though 14 C concentrations indicated the groundwater was predominantly much older than 1000 years.…”

Inactive supply wells as conduits for flow and contaminant migration: conditions of occurrence and suggestions for management

“…1) acted as a conduit partly based on (1) local downward vertical hydraulic gradients and (2) correlation between periods of pump inactivity and concentration increases in deeper water-bearing zones of constituents typically found in shallow water-bearing zones. Bexfield et al (2012), Bexfield and Jurgens (2014), Jurgens et al (2008) and (2014) documented vertical groundwater flow and contaminant migration through municipal supply wells in two different parts of USA (Modesto, California and Albuquerque, New Mexico) during periods of nonoperation. Ambient flow was downwards in one well and upwards in the other.…”

“…Davis et al (1964) measured a maximum flow rate of 478 gal/min (1,852 l/min). Bexfield et al (2012) measured a maximum flow rate of 204 gal/min (772 l/min). Second, only one study presents information regarding the extent of water quality impact.…”