The aquatic habitat team has developed preliminary guidelines for instream flows in the lower Colorado River. The Draft Instream Flow Guidelines cover four types of flows:
- Base flow — average streamflow in the absence of significant precipitation or runoff events.
- Subsistence flow — minimum streamflow needed during critical drought periods to maintain tolerable water quality conditions and provide minimal aquatic habitat space for the survival of aquatic organisms.
- Pulse flow — temporarily increased water flow in a river at specific opportune times that ensure its ecological integrity even if velocity, depth or other qualities decline.
- Overbank flow — infrequent, high-flow event such as a flood that overtops the river banks, physically shapes the channel and floodplain, recharges groundwater tables, and delivers nutrients to riparian vegetation.
The guidelines, developed by BIO-WEST, describe how each flow type would affect aquatic habitat if the project proceeds.
Full report.
Science review panel comments and team response on “Draft Instream Flow Guidelines.”
We invite public comments on these guidelines. Your comments can be e-mailed to me at lcrasawswaterproject@lcra.org, faxed to (512) 473-3551 or mailed to:
Leah M. Manning, Program Manager
LCRA-SAWS Water Project
Lower Colorado River Authority
3700 Lake Austin Blvd.
Austin, Texas 78703
GROUNDWATER FOR AGRICULTURE Land subsidence due to groundwater withdrawal in Colorado, Wharton and Matagorda counties appears to have averaged less than 1 foot since 1900, according to an interim finding by the groundwater for agriculture study team led by URS.
Land subsidence is the sinking of the land surface in response to the removal of subsurface support, which includes groundwater, oil and gas.
The report, Incorporation of Subsidence Modules into the Interim LSWP Groundwater Model, also says that:
- Mining and groundwater withdrawals are potential contributors to land subsidence on a regional scale.
- Land subsidence greater than 1 foot has occurred in localized areas in the three counties where extensive petroleum exploration and sulfur mining have occurred since 1900.
Full report.
AGRICULTURAL CONSERVATIONConservation techniques on farms and in LCRA irrigation canals cost about the same, approximately $120 per acre-foot of water saved, according to a summary of the work done in 2006 by the agricultural conservation team led by Parsons and Texas A&M University.
On-farm conservation measures include precision grading of fields, installation of multiple water inlets, conservation tillage (reduced plowing before planting), and tailwater recovery (capture and reuse of runoff water).
The summary, 2006 Agricultural Conservation Work, also reported that: water conservation goals of 48,000 acre-feet per year for delivery system improvements and 40,000 acre-feet per year for on-farm practices appear achievable.
Full report.
Rice farmers in LCRA’s three irrigation divisions and the Pierce Ranch irrigation district shared production data such as input costs, yields and practices with the socioeconomic study team to help develop models for predicting successful water conservation methods. The meetings were part of the Rice Enterprise Budget study being conducted by CH2M-HILL as part of the socioeconomic study.
The models require cost and return budgets unique to each irrigation division and Pierce Ranch to accurately predict adoption of water conservation practices.
