Monitoring Network of the Groundwater Flow System and Stream-Aquifer Relations in the Mesilla Basin, Doña Ana County, New Mexico and El Paso County, Texas

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The Mesilla Basin monitoring program was established in 1987 to document the hydrologic conditions of New Mexico’s southern-most, Rio Grande rift basin. The program’s data collection and reporting is conducted by the U.S. Geological Survey in cooperation with local, state, and federal agencies. Hydrologic data collected as part of the monitoring program provide valuable information to better understand the geohydrologic system and to support efforts to update, revise, and calibrate basin hydrologic models.

The objectives of this monitoring program are to document the hydrologic conditions within the Mesilla Basin and to establish a long-term continuous data record to permit the quantitative evaluation of the groundwater flow system and stream-aquifer relations.


The monitoring program includes: annual groundwater-level measurements at more than 150 wells, the real-time and monthly monitoring of groundwater levels in nested wells near the Rio Grande, the hourly measurement of water-quality parameters in the shallow alluvial aquifer, a microgravity survey to estimate groundwater storage changes, and discharge measurements made along the Rio Grande to determine gaining and losing reaches.

  1. Mesilla Basin Observation Well Network (MBOWN) (1987 – present) Annual groundwater-level measurements are measured at wells located throughout the Mesilla Valley and the West Mesa area (MBOWN Map). The network includes wells that are completed in the Rio Grande alluvium and in the Santa Fe Group aquifer system (Site List). The groundwater-level measurements and well records are entered into the USGS National Water Information System (NWIS)--Ground-Water Site Inventory (GWSI) database and are available to the public on NWIS Web. Basic statistics for select wells is available at the USGS Groundwater Watch.
  2. Mesilla Valley Hydrologic Sections (1987 – present) The Mesilla Valley hydrologic sections consist of several observation wells aligned perpendicular to the Rio Grande. The location of the Las Cruces hydrologic section (LC-section), Mesquite hydrologic section (M-section), and Cañutillo well-field hydrologic section (CWF-section) are shown on MBOWN map. Diagrams of the Las Cruces, Mesquite, and Cañutillo well-field hydrologic sections show well completion depths and distances from the Rio Grande. Real-time water-level records are maintained at 8 observation wells, and monthly water-level measurements are made at 25 observation wells. Real-time and monthly groundwater data are available to the public at NWIS Web.
  3. Salinity Trends in the Shallow Groundwater (2008 – present) Specific conductance, temperature, and water levels are measured at 1-hour intervals in 9 shallow groundwater wells along the Rio Grande (Salinity Trends map). The continuous water-quality and water-level data are available on NWIS Web.
  4. Microgravity Pilot Study (2015 – 2017) Changes in the acceleration of gravity are precisely measured at 22 locations in the valley near Las Cruces, to estimate the change in groundwater storage of the aquifer (Gravity site map). Many measurements are co-located with existing observation wells to gain a better understanding of the aquifer properties.
  5. Rio Grande Seepage Investigations (RGSI) (intermittent from 1988 – present) Seepage investigations along the Rio Grande were conducted from 1988 through 2015 (Crilley and others, 2013; Gunn and Roark, 2014). Discharge measurements were made at selected sites (RGSI Map) to determine seepage gain/loss from specific channel reaches. Water-quality samples were periodically collected for chemical analyses to determine dissolved solids (salinity), and concentrations of major ions and selected nutrients. Recent drought conditions and decreasing reservoir storage has resulted in a significant reduction in surface-water allocations and therefore limited sites with measurable discharge.


Relevance and Benefits
The Mesilla Basin monitoring network extends through New Mexico and Texas to the United States border with Mexico. The monitoring program will contribute to the USGS mission by providing data to help define the Nation’s water resources, and to disseminate impartial hydrologic information to the public. The program will benefit the cooperators and the USGS by providing essential hydrologic data necessary for subsequent evaluation of the ground-water-flow system and stream-aquifer relations. Ground-water data collected by the program are used in many interpretive studies conducted by the USGS and other agencies including the development and refinement of ground-water-flow models. The long-term monitoring program will document ground-water conditions including stream-aquifer relations, and provide essential data to develop and evaluate water-management strategies.


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Concurrent Programs:

Lower Rio Grande Program

New Mexico's Environment Department and the Interstate Stream Commission are working cooperatively to develop solutions to concerns regarding the quantity and quality of the water delivered to the State of Texas. Elevated salinity in the Rio Grande Project area, which extends from above Elephant Butte Reservoir, New Mexico, to Fort Quitman, Texas, has long been recognized.

NMED and NMISC facilitated the formation of Rio Grande Salinity Management Coalition consisting of water managers, the Rio Grande Compact Commission, and water user groups from Colorado, New Mexico and Texas that are actively working together to reduce and manage salinity in the Rio Grande Project area. In 2009 NMED, ISC, and the US Army Corps of Engineers completed the first phase of a Water Resources Development Act (WRDA) Section 729 Rio Grande Salinity Management Program which included a geospatial salinity database; USGS Rio Grande Salinity Assessment Study; and Rio Grande Economic Impact Assessment study.


New Mexico Water Resources Research Institute Program

The New Mexico Water Resources Research Institute’s (NM WRRI) statewide program supports the state’s water research primarily at New Mexico State University, the University of New Mexico, and New Mexico Tech. Research is conducted primarily by faculty and students within the departmental structure of each New Mexico university campus. In-house staff administers the institute’s programs, conducts special research projects, and produces a variety of issue reports.

The overall mission of the NM WRRI is to develop and disseminate knowledge that will assist the state and nation in solving water problems. NM WRRI administers research projects within a variety of disciplines but that specifically have a focus on water. Users and beneficiaries are local, city, and county government; local water agencies and water users organizations; state agencies (NMDA, NMED, NMOSE, ISC, NMSLO, NMDGF), federal agencies (IBSC, USACE, USBOR, USEPA, USFWS, USGS), and state universities in New Mexico.


Transboundary Aquifer Assessement Program (TAAP)

Recognizing the need to systematically assess priority transboundary aquifers along the U.S.-Mexico border, the 109th Congress of the United States enacted the “United States-Mexico Transboundary Aquifer Assessment Act” in 2006 as Public Law 109-448. This law was followed by binational negotiations that led to the 2009 signing of the “Joint Report of the Principal Engineers Regarding the Joint Cooperative Process United States-Mexico for the Transboundary Aquifer Assessment Program.“ This document, which was signed by US and Mexican Principal Engineers serving on the International Boundary and Water Commission (IBWC), established the authority and framework under which personnel in the United States and Mexico could jointly study shared aquifers. Ongoing projects under TAAP represent a collaboration among the U.S. Geological Survey Water Science Centers and the Water Resources Research Institutes of Arizona, New Mexico, and Texas. Furthermore, IBWC facilitates bilateral projects and collaboration with universities and federal agencies in Mexico such as the Comisión Nacional del Agua and Universidad de Sonora. Currently, identified priority transboundary aquifers include the Hueco Bolson and Mesilla Basin in Texas and New Mexico, and the Santa Cruz and San Pedro aquifers in Arizona. More information about the program, products and partners can be found here.