The Economic Value of Water and Ecosystem Preservation

The majority of the freshwater inflows to San Antonio Bay come from the
Guadalupe and San Antonio Rivers. Historically, the Guadalupe and San
Antonio Rivers have supplied over 79.6% of the total freshwater inflows into this
estuary (Longley, 1994). The gauged areas of the Guadalupe River alone
accounted for 56.9% of the total freshwater inflows into the estuary (Longley,
1994). The Guadalupe River originates in the southern edge of the Edwards
Plateau. The Upper Guadalupe is shallow, with swift flows, receiving inputs from
many minor tributaries that flow intermittently following rainfall events. The San
Antonio River originates within the San Antonio city limits, on the northern edge
of the South Texas Brushlands, and flows in a southeasterly direction. The San
Antonio River joins the Guadalupe River approximately 16 km (9.94 miles) before
entering San Antonio Bay on the Texas coast.
The Guadalupe Estuary has a definite salinity gradient with relatively large
areas having different salinities at intermediate inflow volumes. It has fresher
areas near the Guadalupe River mouth (Mission Lake Guadalupe Bay, Hynes
Bay), and high salinity areas in Espiritu Santo Bay near Pass Cavallo, one of the
major bay-Gulf of Mexico passes.
The Guadalupe Estuary and related wetlands are facing unprecedented
pressure from upstream human water use, as agricultural production, industry,
and rapidly growing urban populations are claiming increasing portions of flows.
Some water authorities have begun to consider the option of reusing treated
effluent rather than allowing it to enter the rivers as return flows that would
provide freshwater to the Estuary. Complicating this problem, some downstream
water rights have been granted based on a certain level of return flows (Kaiser,
1998).
1.2. Legal Setting in Texas Related to Freshwater Inflows
Surface water in Texas is regulated by a permitting system where each water
right has a priority date. Section 11.027 of the Texas Water Code outlines the
principle that those who are “first in time” to apply for a permit are “first in right” to
take or divert surface water and apply it to a defined beneficial use. If there is a
water shortage, the senior rights holders are entitled to extract their share before
the junior holders, who may receive none of their permitted share (State of
Texas, 2005). During a period of extremely low inflows, such as during the
drought of 1956, there is a possibility that water holders may extract all available
water, leaving no inflow to reach the San Antonio Bay.
This possibility has prompted Texas lawmakers to consider mandating that
some freshwater be appropriated for the purpose of maintaining beneficial
environmental flows since currently no permits may be issued to set aside for
environmental needs or bay and estuary inflows. Texas Water Code §11.147
defines a beneficial inflow as “a salinity, nutrient, and sediment loading regime
adequate to maintain an ecologically sound environment in the receiving bay and
estuary system that is necessary for the maintenance of productivity of
economically important and ecologically characteristic sport or commercial fish
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