WSP01461

• File Number: 8549.800
• Description: Rio Grande Basin-Miscellaneous Small Projects and Project Studies-Rio Grande Assessment
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 2/1/1981
• Author: Brandes Kier Stecher
• Title: Water Resources Reference Base for the Assessment of the Rio Grande Region
• Water Supply Pro - Doc Type: Report/Study

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The major aquifer in the Texas portion of the Pecos River basin (WAU
130700) is valley fill that ranges in thickness up to 1,500 feet. There are
approximately 30 million acre-feet of fresh to slightly saline water in
storage, but only about 9.5 to 10 million acre-feet can be withdrawn without
seriously degrading the salinity of the water supply [22].

In addition to the valley fill aquifer, sandstone, limestone, dolomite,
gypsum and basaltic and tuffaceous aquifers also occur within the Pecos
valley and provide limited quantities of water of varying quality. Well
yields range up to 2,200 GPM; but are generally less. The amounts of water
in storage are unknown for most of these secondary aquifers.

The Salt Bolson (WAU 130500) extends southward out of New Mexico between
the Rio Grande and Pecos River valleys. Fill in the bo1son includes coarse
alluvial fan deposits, fine grained lacustrine deposits and volcanic rocks.
Thickness ranges up to 4,500 feet, and well yields generally are less than
200 GPM. The total amount of fresh water in storage is estimated to be 6.5
million acre-feet, of which 5.7 million acre-feet are recoverable. Limestone
and volcanic aquifers are locally productive.

Ground water resources downstream from the confluence of the Pecos River
with the Rio Grande are limited; surface water provides the main source of
supply. The principal aquifer within the Devils River basin (WAU 140303) is
the Edwards-Trinity which is comprised of poorly to well consolidated
sandstone overlain by limestone and dolomite. Between the mouth of the
Devils River and the Gulf Coastal Plain (WAU 130800), the principal aquifer
available is the Carrizo-Wi1cox, composed primarily of poorly to well con-
solidated sandstone, siltstone and mudstone. Rio Grande alluvium is the
principal aquifer in the Gulf Coastal Plain (WAU 1309001. Well yields range
up to approximately 3,000 GPM; the limestone aquifer is the most productive.
The total amount of fresh and slightly saline water available in the three
WAU's is estimated to be about 20 million acre-feet [19].

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