Rio Grande Salinity Management — A Real Possibility?

Dale Doremus – New Environment Department and Gregory Lewis – Interstate Stream Commission ncreasing salinity in the Grande. Utilization of water resources in Preliminary studies indicate that from the Rio Grande Project area is restricted interception may be feasible where highly in New Mexico to Fort Quitman, where highly saline water results in saline groundwater upwells into the ITexas has been documented for reduced potable water supplies, smaller shallow aquifer system. For example, one roughly 100 years (Stabler, 1911), and crop yields, and soil and groundwater shallow monitoring well in the El Paso predates construction of the Federal deterioration. Salinity concentrations in Narrows area yields groundwater with Rio Grande Project in this area. the Rio Grande are higher in the winter, a total dissolved solids concentration of when the flow is comprised mostly of over 30,000 mg/l. Interception through Recent research has identified natural relatively saline shallow groundwater. pumping wells of even modest volumes sources such as the upwelling of deep- In season, reservoir releases of such highly saline groundwater in circulating groundwater and geothermal of fresher water dilute the salinity. The source areas prior to its commingling waters as the principal salinity contributors higher salinity levels currently preclude with surface water could significantly in the region. Additionally, these natural the cities of El Paso and Ciudad Juarez lower salinity levels in the Rio Grande salinity inputs appear to be localized, from using the Rio Grande for municipal and increase available potable water suggesting that source control and water supply in nonirrigation months. supplies in the critical /New Mexico treatment may be feasible. Phillips border region (Hogan and others, 2007). and others (2003) showed that salinity 25 increases from about 40 milligrams per The First Step Toward Management liter (mg/l) to about 2,000 mg/l in a 750- To tackle the unique salinity challenges of mile stretch of the Rio Grande occur in the Rio Grande, the Rio Grande Compact steps, with large increases localized at the Rio Grande Elephant Butte Reservoir Commission (RGCC), in collaboration southern ends of sedimentary subbasins, Truth Or with local water management entities, Consquences for example, at San Acacia, Elephant TDS SAMPLING SITE has initiated a multi-state effort to create Below Butte (Truth or Consequences), Selden Caballo Period of record 1938–2007 a Rio Grande salinity control program, Canyon, and the El Paso Narrows (see Reservoir Irrigation season 551 mg/L Non-irrigation season 741 mg/L administratively patterned after the map). In order to quantify the flux of successful Colorado River Salinity Control brines discharging from these sedimentary TDS SAMPLING SITE Below Leesburg Dam Forum (see page 22). As an initial step, basins, isotopic data have been used Period of record 1938–2007 the RGCC hosted a Rio Grande Project Irrigation season 548 mg/L to fingerprint and separate potential Non-irrigation season 857 mg/L Salinity Management Workshop in Selden Canyon sources (Hogan and others, 2007). May 2007. The workshop objectives were to identify ways to improve Rio Las Cruces Investigations in the El Paso Valley Grande water quality by reducing 10 (Hibbs and Merino, 2007) attribute a salinity in the New Mexico-Texas different geologic source, specifically, US Irrigated Lands border region, and to establish a the dissolution of a buried evaporite NEW MEXICO technical basis for a multistate deposit, as the primary source of salinity TEXAS salinity management program. near Fabens, Texas. Hibbs notes, El Paso however, that “use of an already saline Attended by over 100 alluvial groundwater for irrigation TDS SAMPLING SITE Courchesne Bridge Cuidad participants, the conference appears to accelerate evaporative Period of record 1934–2007 Juarez brought together federal, Irrigation season 841 mg/L salinity enrichment of irrigation Fabens Non-irrigation season 1488 mg/L MEXICO state, and local water, leading to greater potential for water managers, development of salt-encrusted soils.” Salinity concentrations in the Rio Grande researchers, increase downstream, especially during the nonirrigation and water 10 Recent water quality studies point (winter) season when proportionally more of the flow is user groups to the feasibility and desirability of contributed by saline groundwater, including agricultural drains. Large reservoir releases of less saline water reduce Fort Quitman from Texas, managing salinity inputs to the Rio salinity concentrations during the irrigation season. New Mexico,

24 • March/April 2008 • Southwest Hydrology Colorado, Arizona, Utah, California, and participation from local entities, as well • Identify specific project sites Chihuahua who were interested in Rio as state and federal water managers. The where saline water is adversely Rio Grande Salinity Management — Grande salinity issues. The workshop was formation of a multistate coalition of affecting the human use of surface effective in improving understanding of stakeholders to develop a Rio Grande water or groundwater and where A Real Possibility? sources of Rio Grande salinity, particularly salinity management program in the reductions in salinity could increase in the Rio Grande Project region, the available water supply. defining socioeconomic implications Recent water quality • Conduct feasibility studies for of increasing salinity, and exploring salinity capture and treatment in potential salinity management strategies studies point to the Rio Grande Project region. to reduce impacts and extend existing the feasibility and water supplies in this fast-growing area. desirablility of Contact Dale Doremus at [email protected]. Discussion focused on how elevated managing salinity salinity can restrict the full utilization of References inputs to the Hibbs, B., and M. Merino, 2007. Discovering a water resources by reducing 1) available geologic salinity source in the Rio Grande potable water supplies, 2) crop yields Rio Grande. Aquifer, Southwest Hydrology, 6(4): 20-21. and profitability, 3) the quality of urban Hogan, J.F., F.M. Phillips, S.K. Mills, and others, New Mexico/Texas border region is 2007. Geologic origins of salinization in a landscapes, and 4) soil and groundwater semiarid river: The role of sedimentary basin in the beginning stages. Proposed quality. All water-use sectors, including brines, Geology, 35(12): 1063-1066. objectives for the program include: Phillips, F.M., J.F. Hogan, S.K. Mills, and J.M.H. residential, commercial and industrial, Hendrickx, 2003. Environmental tracers applied agricultural, and water utilities themselves • Develop a work plan for funding and to quantifying causes of salinity in arid- are affected by adverse economic impacts implementation of target projects region rivers: Preliminary results from the Rio Grande, Southwestern USA, in Water Resources of elevated salinity. Some specific where reduction in salinity could Perspectives: Evaluation, Management and issues that were covered include: increase the available water supply. Policy, ed. by A.S. Alsharhan and W.W. Wood, New York, Elsevier, pp. 327-334. • Attain congressional support for • Elevated salinity is not addressed Stabler, H., 1911. Some stream waters of the western by conventional municipal federal funds for salinity control , USGS Water Supply Paper 274, supply treatment; a separate and mitigation projects. U.S. Dept. of the Interior. desalination process is required. • Consumer preference is the ultimate discriminator for acceptable dissolved solids in municipal water supplies. • The Lower Colorado River Basin states’ salinity damage model estimated total annual quantifiable salinity damages of $376 million for all categories. • A rigorous economic evaluation of Rio Grande salinity damages is needed to better quantify the impacts of elevated salinity, and to determine what level of investment in salinity control is appropriate and justified. • Previous studies including those from other regions can be helpful, but Rio Grande economic damages must be based on local conditions.

Additional information and materials from the workshop are available on the web at www.ose.state.nm.us/ special_projects_rgpsmw_menu.html.

In the Works An effective salinity management program will require both commitment and active

March/April 2008 • Southwest Hydrology • 25