USGS MIDDLE RIO GRANDE BASIN STUDY - STATEMENT OF INTEREST

Dave Hester
USGS - Rocky Mountain Mapping Center
dhester@usgs.gov
(303) 202-4318

The U.S. Geological Survey (USGS) Middle Rio Grande Basin (MRGB) Study is a 5-year effort by the USGS and other agencies to improve the understanding of the hydrology, geology, and land-surface characteristics of the Middle Rio Grande Basin. The Santa Fe Group aquifer is the main source of municipal water for the region. The New Mexico State Engineer Office manages the water resources in the basin and has declared the basin a "critical basin"; that is, a ground-water basin faced with rapid economic and population growth where there is less than adequate technical information as to the available water supply. The USGS will study the hydrology, geology, and land-surface characteristics of the basin to provide the scientific information needed for land use and water-resource planning. The study began in 1995 and shall be completed in 2000.

The Middle Rio Grande Basin is the area within the Rio Grande Valley extending from Cochiti Dam downstream to the community of San Acacia. The study area contains approximately 3,000 square miles and includes the Albuquerque/Santa Fe urban corridor. In the next few years, the City of Rio Rancho will surpass the City of Santa Fe as the second most populous municipality in the State of New Mexico. The Bureau of the Census has projected that the region's population could swell by 55 percent by the year 2025. The Middle Rio Grande Council of Governments projects an additional 700K people will be added to the region for a total population of 1.5 million by the year 2050.

In 1995, the USGS published the results of a 2-year study of the Santa Fe Group aquifer, which serves as the main source of municipal water supply for Albuquerque and other communities in the Middle Rio Grande Basin. This earlier study simulated water levels in the aquifer through the year 2020 using four different water-use scenarios. The study found that the quantity of water in the aquifer available for municipal supply was significantly less than previously estimated. Because approximately 600,000 people (40 percent of the population of New Mexico) live in the study area, water shortfalls could have serious consequences for the State. Recent projections indicate that the Santa Fe Group aquifer may be depleted by the year 2060.

Ground-water withdrawals in the region are also causing other environmental problems such as land subsidence and contamination of existing wells due to nitrate leaching. As a consequence of sole reliance on ground-water for domestic water supplies, the City of Albuquerque has acquired 48,000 acre-feet of surface water rights known as the San Juan-Chama project. However, delivery of San Juan- Chama water to the City of Albuquerque will not occur until the year 2003. Even though the Rio Grande water is all appropriated and the San Juan-Chama water is not yet available, the City of Albuquerque continues to entice major water users such as microprocessor manufacturer, Intel, to the region without contemplating the long-term sustainability of those development decisions. Water rights adjudication is already occuring in the Lower Rio Grande region of the State and eventually the problem may migrate to the Middle and Upper Rio Grande Valley.

As part of the USGS MRGB Study, the National Mapping Division (NMD) plans to characterize the land surface of the region. NMD shall integrate thematic data layers in order to derive a composite land development attractiveness value. Researchers will investigate alternative land use development scenarios for expanding water needs for the timeframes of 2020 and 2050 as part of the land surface analysis. Historically, man's impact on the landscape has caused land cover to evolve into land use. Specific land uses are more conducive to ground- water recharge and conducting a trend analysis will allow researchers to determine the long-term impacts on the land surface. Consequently, NMD shall compile temporal LULC snapshots (i.e., 1930's, 1950's, 1970's, and 1990's) that will be used for trend analysis as well as to forecast future land use patterns. Predicting future land use demand shall be modelled by associating specific land use categories with the ability to absorb regional socioeconomic forecasts for population and employment growth.

Dave Hester is presently functioning as the MRGB Project Manager for the NMD.