(GP/GT) for Additional Water Supply in the Lower Rio Grande

1-2
1. GP/GT Fairways
Information provided by Mr. R. W. Rodgers, Professor of Geology at U.T./Pan American,
Edinburg, Texas. The identity of each letter presented in this overlay is as below:
A -
B -
C -
D -
Coastal Miocene Trend(includes prospective reservoirs studied under recent USDOE
Contract No. 2069)
Lower-Salinity Frio Trend
Frio-Vicksburg Trend
Vicksburg Trend
Professor Rodgers has qualitatively ranked the overall potential of these Fairways as shown
below:
Fairway
A
B
C
D
Rankini
Medium
Medium
High
Low
2. Productive Zones of MUdly/Moderately Brackish Groundwater
Most of the information ,utilized in this layer was obtained from Figures 5 and 12 of the TWDB
Report No. 316 entitled: "Evaluation of Groundwater Resources in the Lower Rio Grande Valley,
Texas" (1990). Figure 5 is entitled: "Approximate Productive Areas of The Major Sources of
Groundwater in the Lower Rio Grande Valley" and Figure 12 is entitled: "Chemical Quality of
Water in the Evangeline and Chicot Aquifers". The approximate configuration of the 5,000
mg/l.TDS contour line was taken from Figure 7 of the Texas Department of Water Resources
Report No. 279, entitled: "Occurrence and Quality of Groundwater in the Vicinity of
Brownsville, Texas (1983)". Figure 7 is entitled: "Dissolved Solids Concentration in Water from
The Deep Zone". Copies of several of these Figures are enclosed in this Report.
The identity of each number presented in this overlay is as follows:
(1) - Upper Part of Chicot Aquifer: Alluvial Deposits of the Rio Grande (Recent and
Pleistocene)
(2) ~ Middle Part of Chicot Aquifer: Beaumont Formation (pleistocene)
(3) - Lower Part of Chico Aquifer and Evangeline Aquifer: Lissie Formation (pleistocene) and
Goliad Formation (pliocene)
(4) - Oakville Sandstone(Miocene).
3. Population Densities
Base Maps of Cameron and Hidalgo Counties were utilized to represent the population densities
of both incorporated and Colonia areas of each county. It is our understanding that these maps
were the basis for the information in the TWDB Report entitled: "Water and Wastewater for the
Colonias of the Lower Rio Grande Valley of Texas"