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

The possibility exists for this lower section to be cut by
faulting, but the sand is persistent and laterally continuous
throughout the area of key well control.
Reservoir Area B
Reservoir Area B is bounded on the west by the Donna fault
which extends from the Rio Grande northward into Willacy county.
It is bounded on the east by the Weslaco fault which extends from
the Rio Grande northward along the Cameron County-Hidalgo County
line into Willacy County (Fig. 1). within area B, the reservoir is
bounded on the south and north by lines which define the limits of
key well control (Fig. 2).
Small faults associated with both the
Donna and Weslaco faults limit the reservoir to the north.
The
reservoir may extend somewhat farther to the south, but the extent
is limited based on available well control. The south edge of the
reservoir is not affected by the Shepherd fault which limits the
south edge of reservoir area C.
within the area outlined, the
reservoir could contain as much as 120 square miles (Fig. 2).
Within the area of Reservoir B there are numerous thick sands
below the top of the geopressured zone.
The "10,000 foot" sand is
below the top of the geopressured zone, and is laterally continuous
within the area.
Additionally, this sand has the lowest reported
salinity (4,000 ppm CI) of any of the sands for which data are
available.
The top of the sand occurs at 9,550 feet on the west
side of the reservoir and at 10,360 feet on the east side. The dip
is relatively flat across the top of the Weslaco high or "uplift,"
although the dip angle begins to increase markedly at greater
depth.
II-II