1. Water Quality and Environmental Flows
Maintaining Quantity for Quality’s Sake
Presented By: Jennifer Benaman
Quantitative Environmental Analysis, LLC
November 1, 2005

2. maintain aquatic habitat Freshwater inflows for
Project Overview
Water for rural
communities
Higher water levels
in Highland Lakes
Lake
Buchanan
Austin
Instream flows to
maintain aquatic habitat
Water for San Antonio
San Antonio
Water for agriculture
(up to 150,000 ac-ft/yr)
Stakeholders in both regions benefit-”Win-Win” Project
Colorado Basin
Water for upstream rural communities
Highland lake levels are more stable during dry periods, specifically raising the average water levels of Lakes Travis and Buchanan during these periods
Riverine and terrestrial environment is protected by maintaining adequate instream flows in the Colorado River
Water for agriculture (to maintain a $300M economy vital to this state)
The Matagorda Bay is protected
San Antonio region - SAWS gets water
At affordable costs
Reliably delivered
Over long term
Freshwater inflows for
Matagorda Bay
file name LSW11_ _._ _

3. How will the project conserve and develop 330,000 acre-feet of water?
Maintain higher water levels
in Highland Lakes
How will the project conserve and develop 330,000 acre-feet of water?
Colorado
Columbus
Build Off-Channel Storage P
Use Groundwater for Agriculture when Surface Water Insufficient
Conserve Agricultural Irrigation Water
Wharton
Wharton
Bay City
Matagorda
The lower Colorado River Basin's irrigation demands will be reduced due to conservation, build new off-channel storage facilities to capture water from the river, pump groundwater when surface water is insufficient, change how Highland Lakes are operated to slightly reduce the amount of water taken from them, and use more run of river flows, all of which when combined will meet all of the own remaining in-basin needs and leave up to 150,000 acre-feet for San Antonio. Only when done as a combined system can the project goals be achieved.
Provide beneficial Inflows
Matagorda Bay
file name LSW11_ _._ _

4. State Legislative Requirements
As per HB 1629, the project must
Protect and benefit basin interests
Be consistent with state regional water plans
Provide inflows adequate to maintain ecological health and productivity of Matagorda Bay
Maintain current instream river flow protections
Ensure San Antonio practices stringent conservation measures
Provide broad public and scientific review process
Benefit stored water levels in Lakes Travis and Buchanan
file name LSW11_ _._ _

5. Environmental Study Teams
Matagorda Bay Health
Respond to the mandate that bay inflows remaining after any Project diversions will be adequate to maintain the health and productivity of the Matagorda Bay System
Aquatic Habitat/Blue Sucker
Study the impact of the LSWP on the riverine habitats in the river below Austin
Water Quality
Study the impact of the LSWP on the water quality of the river
file name LSW11_ _._ _

6. Matagorda Bay Health Evaluation
Detailed analysis of inflows to the bay system, both from the Colorado River and the coastal drainage system into the bay which stem in part from return flows from irrigation areas
Salinity modeling of the bay system including the marsh systems on the northern boundary of Matagorda Bay and East Matagorda Bay
The effects on bay habitat of various freshwater inflow regimes
The effects of changes in inflow on bay food supply (nutrients and sediment)
Development of statistical relationships between inflow and biota
Synthesis of these various components of “bay health”
file name LSW11_ _._ _

7. River Water Quality Implications
Current LCRA Water Management Plan
Release stored water from Highland Lakes for downstream irrigators during summer
Net effect: summer flows higher than “natural”
Potential Effect of LSWP
Irrigators obtain water from local (downstream) sources.
More frequent low flows in summer
Changes in the timing, duration, and frequency of low flows may affect water quality
file name LSW11_ _._ _

8. River Model Approach Use state-approved QUAL-TX
Focus on critical low flow condition
Expand TCEQ grid
Collect additional data to constrain model
Calibrate to new data, scale to warmer temperatures
Future critical condition anticipated to be in summer
Perform future simulations in coordination with expected flow regime
Longhorn Dam
Smithville
TCEQ grid
New grid
file name LSW11_ _._ _

9. New Data Collection Water quality under “low-flow”/warm conditions
Dye tracer for hydraulic characterization
Diel DO for daily dissolved oxygen fluctuations
Bay habitat mapping
Salinity data for model development in the bay
file name LSW11_ _._ _

10. For Additional Information
file name LSW11_ _._ _