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The State of the Bay Galveston Bay Area Project

Galveston Bay Freshwater Inflows Group (GBFIG)

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Agendas & Summaries
Two major rivers, the Trinity and the San Jacinto flow into Galveston Bay. Cities and farms upstream of the bay on these rivers require water for use in homes, industries, and farms. The flow of fresh water is also essential to the living and non-living components of the Bay.

The Galveston Bay estuary is a transitional zone where the saline waters of the open ocean mix with the fresh water flowing from rivers. Inherent to this mixing zone are a host of physical conditions and processes which include varying salinity regimes, water circulation patterns, nutrient influxes, sedimentation processes, and freshwater inflow patterns. These physical conditions and processes in turn have a profound effect on the Bay's biological components by impacting the recruitment of juvenile fish, the location of oyster reefs and other benthic communities, and the establishment of emergent marshes.

The Galveston Bay Freshwater Inflows Group (GBFIG) includes staff from relevant natural resource agencies, representatives from environmental groups, fisheries and agricultural interests, and water district managers. The group has been meeting since 1996 to devise strategies to maintain adequate freshwater inflows to Galveston Bay.

After reviewing relevant scientific and technical information, GBFIG members will construct potential management strategies to ensure that Galveston Bay continues to receive adequate fresh water while protecting the interests of citizens living in the Trinity and San Jacinto watersheds.

Relevant to their efforts is Texas Senate Bill 1 (SB1). In 1997, the Texas Legislature, through SB1, directed the Texas Water Development Board to construct regional water plans every five years. The state is divided into 16 regions and Galveston Bay is in Region H (view the
Region H Plan).

After reviewing water availability and demand models, GBFIG recommended that the Region H Planning Group consider environmental flows when constructing its regional plan. The Group noted that successful management of inflows to Galveston Bay must consider quantity, quality, seasonality (monthly flows), and location of inflows. The chart below contains the group's recommendations.

Inflow Scenario Quantity Needed
Target Minimum
Max H 5.2 million 66% 50%
Min Q 4.2 million 70% 60%
Min Q-Sal 2.5 million 82% 75%
Min Historic 1.8 million 98% 90%

Scenario Descriptions

Max H:

Inflows required for maximum bay and estuary fisheries harvest as recommended by Texas Parks and Wildlife Department.

Min Q:

Minimum inflow required to maintain the bay and estuary fisheries harvest.

Min Q-Sal:

Minimum acceptable inflow required to maintain the salinity needed for bay and estuary fisheries productivity.

Min Historic:

Minimum annual inflows recorded for Galveston Bay over the period of record (1940-1990).



GBFIG Work Plan (revised June 2000) (31.3 kb)

Online Resources:

Environmental Flows Advisory Committee
TPWD Environmental Target Flows
TWDB Regional Water Plans
TCEQ Water Availability Models
Bayou Preservation Association Stream Classifications


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