New Mexico Water Science Center
NEW MEXICO PROJECTS
Changes in groundwater levels in the Albuquerque metropolitan area
Project Chief: Matt Ely
The U.S. Geological Survey, in cooperation with the Albuquerque Bernalillo County Water Utility Authority (ABCWUA) has been investigating the effects of groundwater withdrawal on groundwater levels throughout the Albuquerque metropolitan area in the Middle Rio Grande Valley of central New Mexico (fig. 1). Historically, the water supply requirements of the Albuquerque metropolitan area were met almost exclusively by groundwater withdrawal from the Santa Fe Group aquifer system. In response to water-level declines, the ABCWUA began diverting surface water from the San Juan-Chama Drinking Water Project in December 2008 to reduce the use of groundwater to meet municipal demand. Consequently, there is currently (2014) an interest in understanding how groundwater levels have changed over time in response to groundwater pumping and the recent addition of surface water resources.
The population of the City of Albuquerque and the Albuquerque metropolitan area has grown rapidly over the past several decades. For example, the City of Albuquerque population increased fivefold between 1950 and 2010 (fig. 2). With these population gains came increases in the demand for groundwater resources. Water conservation measures have reduced per capita water use substantially over the past 25 years. Groundwater withdrawal peaked in 1989 and has been decreasing since (fig. 2), but continued groundwater level declines indicate that withdrawal was still in excess of recharge.
Two new USGS reports have been developed that investigate the variability and extent of groundwater level changes throughout the Albuquerque metropolitan area as well as the more recent effects of reduced groundwater use following the introduction of surface water supplies. The first (Powell and McKean, 2014) provides an estimate of the 2012 potentiometric surface of the production zone (the interval of the aquifer where the bulk of groundwater occurs, typically between 200-900 feet below the water table) of the Santa Fe Group aquifer system. The second (Rice and others, 2014) presents maps showing water levels and water-level change by contouring water-table elevations and production zone hydraulic heads (the elevation at which water will stand in a tightly-cased well) that were simulated with a recently-updated regional-scale transient groundwater flow model (Bexfield and others, 2011) at 10-year intervals from 1950 to 2000 and again for 2008. Both reports also investigate changes in groundwater levels recorded from nine selected groundwater level measurement sites that are recorded and summarized by USGS (Beman, 2013).
The 2012 potentiometric surface map indicates that the general direction of groundwater flow is from the Rio Grande towards clusters of supply wells in the east, north, and west parts of the Albuquerque metropolitan area. The results of the modeled decadal-scale maps show little change from steady-state (1900) conditions until the 1970s and 1980s, when population increased dramatically. Areas with substantial groundwater declines appeared during this time in the eastern part of the metropolitan area, then appeared on the western side of the basin as pumping expanded with the increasing population. Large declines of over 140 feet were observed in both the water table and in the production zone. In general, patterns of simulated declines in production-zone hydraulic heads are similar to those in the water table, with the largest declines seen in proximity to major pumping centers. The production-zone, however, shows a more extensive area of decline because this is the depth interval where the majority of the withdrawal stresses are being applied to the Santa Fe Group aquifer system.
While groundwater level declines are substantial in many areas, hydrographs (graphs of water level change) show several instances where groundwater levels have increased since the introduction of surface water supplies from the San Juan-Chama Drinking Water Project. However, the surface water supplies are only reducing groundwater reliance for the City of Albuquerque; other parts of the metropolitan area where groundwater remains the sole source of supply continue to experience groundwater level declines.
Analysis of the magnitude and spatial distribution of water level change can help improve the understanding of how the groundwater system responds to withdrawals. This information can support efforts to minimize future water-level declines may inform the development of strategies for maintaining a sustainable groundwater reserve in the future.
The report, “Simulated and measured water levels and estimated water-level changes in the Albuquerque area, central New Mexico, 1950-2012”, by Steven Rice, Gretchen Oelsner, and Charles Heywood, is published as U.S. Geological Survey Scientific Investigations Map 3305 and is available on the Web at (http://pubs.usgs.gov/sim/3305/)
A groundwater model developed for the Santa Fe Group aquifer system that was used to develop the water-level change map series (Rice and others, 2014) is found at: http://pubs.usgs.gov/pp/2011/1737b/pdf/Section2.pdf