Observed Variability in Groundwater Quality in the Rincon Valley, NM through High-Frequency Monitoring
Tuesday, February 27, 2018: 8:30 a.m.
Laura Bexfield
,
USGS, Albuquerque, NM
Since 2014, the USGS National Water Quality Assessment Project has been collecting high-frequency (daily) data for water-quality parameters at three wells in the Rincon Valley, New Mexico, to better understand how groundwater quality changes over short (daily to monthly) and long (seasonal to decadal) timescales. After daily purging of the two monitoring wells and one irrigation well, single measurements of water temperature, specific conductance (SC), pH, and dissolved oxygen are transmitted to the National Water Information System, where they are available for near real time viewing (https://waterdata.usgs.gov/nm/nwis/current/?type=quality&group%20Key=basin%20cd). Water levels are recorded every 15 minutes. Groundwater samples are collected annually for analysis of major and trace elements, nutrients, pesticides, and selected environmental tracers. Bimonthly sampling (planned to begin in 2018) is intended to help correlate high-frequency water-quality parameters with constituents of interest, including dissolved solids, nitrate, and uranium.
Land use in the Rincon Valley, located along the Rio Grande in southern New Mexico, is dominantly agricultural, and water management in the valley is highly dependent upon the annual availability of surface water for crop irrigation. Water levels in all three study wells, which represent different depths (6.7 to 18 m) and positions within the groundwater flow system, have generally risen over the period of record. However, the sites differ with respect to the direction of multi-year SC trends, as well as the seasonality and general variability of water-quality parameters. Annual dissolved-solids concentrations typically correlate with multi-year SC trends, but annual concentrations of individual major and trace elements, nutrients, and pesticides tend to be variable. Age tracers indicate that the sites have differing fractions of young (post-1950) recharge and older regional groundwater. Temporal patterns in water quality at the three sites likely illustrate the effects of various hydrologic factors and conditions, including the release, pumping, and application of water for crop irrigation.
Laura Bexfield, USGS, Albuquerque, NM
Laura Bexfield has been a hydrologist in the New Mexico Water Science Center of the U.S. Geological Survey since 1993. She currently contributes to the Groundwater Status and Trends Team of the National Water-Quality Assessment project. During her 24 years with the USGS, she has been involved with multiple projects characterizing groundwater chemistry and groundwater flow systems across the Southwest.
