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United States Department of Agriculture

Agricultural Research Service

Title: Competing Interests and Concerns in the Rio Grande Basin: Mountain Hydrology, Desert Ecology, Climate Change, and Population Growth

Author
item RANGO, ALBERT

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2004
Publication Date: N/A

Technical Abstract: In the mountainous American Southwest, the Rio Grande basin is a prime example of how conflicts, misconceptions, and competition regarding water can arise in arid and semi-arid catchments. Much of the Rio Grande runoff originates from snow fields in the San Juan Mountains of southern Colorado and the Sangre De Cristo Mountains of northern New Mexico, far from population centers. Large and rapidly growing cities, like Albuquerque, Las Cruces, El Paso, and Juarez, are located along the Rio Grande where it flows through the Chihuahuan Desert, the largest desert in North America(two NSF Long Term Ecological Research sites are located in the desert portion of the basin). As a result, the importance of snowmelt, which makes up 50-75% or more of the total streamflow in sub-basins above Elephant Butte Reservoir(in south central New Mexico) is hardly known to the general public. Streamflow below Elephant Butte Reservoir is rainfall driven and very limited, with the lower basin receiving only 170-380 mm of precipitation annually, most of it occurring during the months of July-September. Extreme events, such as drought and flooding, are not unusual in arid basins, and they are of increasing concern with regard to changes in frequency of such events under the impending conditions of climate change. Current water demands in the basin already exceed the water supply by 15% or more, so streamflow forecasts(especially from snowmelt runoff) are extremely valuable for efficient water management as well as for proper apportionment of water between Colorado, New Mexico, and Texas under the Rio Grande Compact of 1938 and between the U.S. and Mexico under the Treaty of 1906. Other demands on the water supply include Indian water rights, flood regulation, irrigated agriculture, municipal and industrial demands, water quality, riverine and riparian habitat protection, endangered and threatened species protection, recreation, and hydropower. To assess snow accumulation and cover and to produce streamflow forecasts, several techniques are being employed including manual snow surveys, automated SNOTEL measurements, satellite snow cover extent measurements, development of snow cover depletion curves, and input of these data to the Snowmelt Runoff Model(SRM) and other models for forecasting. Early season(November-January) SNOTEL measurements of snow water equivalent can be used in regression approaches to estimate streamflow volumes early enough to provide growing season planning for the types of crops to plant. Satellite snow cover is used directly in SRM for daily flow forecasts throughout the melt season starting as early as March. Additionally, SRM can automatically produce future hydrographs for climate change scenarios. For large river basins in arid and semi-arid areas, new technologies, like remote sensing, will be valuable in assisting water managers to make more efficient use of their limited water supply. Additionally, like meteorologists have done for the last 40 years, hydrologists need to make use of remote sensing data to communicate in real time with the public on the effects of snow accumulation, melt, and snowmelt runoff on human activities.

Last Modified: 9/29/2014
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