1. The Secondary Water Supply for Laredo?
The Problem:
• The Rio Grande is not infinite!
• The City of Laredo has rights to about 40 mgd
• ALSO CONSIDER DROUGHT
- Falcon and Amistad as of late has recorded
record low volumes of water
So there is a clear need to develop a secondary water supply
for the City of Laredo.

3. Some Geology:
Since our water supply is surface-based, which is subject to our
highly variable climate it makes sense to consider groundwater
as a potential secondary water source.
To understand groundwater one must know a little geology
Relevant Terms:
Superposition Regional Dip
Recharge Area Porosity
Permeability

4. Webb County Geology

6. The Possibilities:
Edwards/Trinity Aquifers (Using the Rio to transport the water
from Kinney County)
Laredo/Carrizo Aquifers (Within 10 miles of the city)
Carrizo Aquifer (Northwest Webb County)
Carrizo Aquifer (Dimmit County)
Major Difficulties:
There are significant problems with all of these possibilities is
that the cost is 3 to 6 times more than obtaining and treating
water directly from the Rio Grande.

7. Edwards/Trinity Aquifers (Using the Rio to transport the water
from Kinney County)
Problem: Effectiveness depends
on maintaining minimum flow within the Rio Grande
Does not help during
Drought situations

8. Webb County Geology

9. Laredo/Carrizo Aquifers (Within 10 miles of the city)
Problem: High Total dissolved Solid (TDS) content.
Can not drink this water!
Need desalination plan

10. Laredo/Carrizo Aquifers (Within 10 miles of the city)
Main Problem:
For desalination to be cost effective need aquifers with very high
permeabilities and hydraulic conductivities
• NEED MINIMUM OF 5 MGD
The Laredo/Carrizo aquifers in the Laredo area have relatively
low hydraulic conductivities.
• Can not pump water out of these aquifers at needed rates
Other Issues:
Pipeline Interstructure
Brine Disposal
Depletion of Aquifers
- VERY LOW RECHARGE RATES
< 1 in/yr

11. Carrizo Aquifer (Northwest Webb County)
Transfer of water by:
Rio Grande River (Note Previous Objections)
Pipeline (Nearly doubles cost)
Water quality not as good as Carrizo water from closer to the
recharge zone in Dimmit County
Carrizo Aquifer (Dimmit County)
Political Cooperation with Dimmit County may be difficult

12. Webb County Geology

13. Thinking Outside the Box:
Interbasinal Water Transfers
• Perhaps from eastern Texas
Q: What is the problem with this concept especially during
a drought?
Aquifer Storage and Recovery
• Pump Rio Grande water into local aquifers (Laredo/
Carrizo)
- Problems - Clogging of Wells
SILT
CALCITE ENCRUSTATION

14. Storage of Water in Lake Casa Blanca
• Pump Water from Rio Grande into Lake Casa Blanca
Good as only a short-
term solution
Also, excessive
evaporation during
severe drought
conditions can rapidly
deplete this resource

15. ¿Aqua por colonias?