The term "environmental flows" is used to describe the flow of water (both quantity and timing of flow) needed to maintain ecologically healthy streams and rivers, as well as the bays and estuaries that they feed. Healthy aquatic ecosystems conserve biodiversity and support many industries, including recreation, tourism, commercial fishing, transportation, and water supply. With the population of Texas projected to increase 82 percent in the next 50 years, the demand for water is anticipated to exceed current supply, requiring increased usage of both surface water and groundwater resources. Without adequate provisions to protect environmental flows (while also balancing other needs), additional demands for water could reduce or alter flows potentially leading to degraded aquatic and coastal ecosystems.
To address this concern, the Texas Legislature set in place two directives, Senate Bill 2 (2001) passed by the 77th Texas Legislature and Senate Bill 3 (2007) passed by the 80th Texas Legislature, to aid in balancing human and environmental water needs. Environmental flow studies in Texas currently are being conducted under these two major legislative directives.
Texas Instream Flows Program (Senate Bill 2)
In 2001, Senate Bill 2 directed the Texas Parks and Wildlife Department (TPWD), the Texas Commission on Environmental Quality (TCEQ), and the Texas Water Development Board (TWDB), in cooperation with other appropriate agencies, to "jointly establish and continuously maintain an instream flow data collection and evaluation program." In addition, the legislature directed the agencies to "conduct studies and analyses to determine appropriate methodologies for determining flow conditions in the state rivers and streams necessary to support a sound ecological environment." The resulting program, known as the Texas Instream Flows Program (TIFP), conducts detailed instream flow studies which consider a wide range of environmental variables such as habitat, hydrology, biology, physical processes, water quality, and connectivity - all dictating a multidisciplinary effort. The goal of each study is to identify appropriate flow regimes that conserve fish and wildlife resources while also providing sustained benefits for other human uses of water resources. Given their complexity, instream flow studies take many years to complete with only a small portion of the State's rivers having been addressed to date.
Environmental Flows Process (Senate Bill 3)
Whereas Senate Bill 2 provides for detailed studies and determinations of the instream flow needs for priority river basins, the Legislature recognized the need to more quickly identify appropriate amounts of water to set aside for the environment and so passed Senate Bill 3 in 2007. Senate Bill 3 (SB3) is an accelerated, stakeholder-driven process designed to use existing information and the best available science to establish environmental flow recommendations and standards for all Texas river basins and estuaries. The timing of the process does not allow for the completion of new, more detailed studies. However, an adaptive management component allows for refinement of flow recommendations at least every 10 years. Results of more detailed technical studies, such as those completed by the Texas Instream Flow Program, will be available to inform future refinements of environmental flows.
Texas has a long history of evaluating the environmental flow needs for bays and estuaries under several legislative directives, Senate Bill 137 (1975), House Bill 2 (1985), Senate Bill 683 (1987), and Senate Bill 1 (1997). These earlier efforts to determine freshwater inflow needs to the estuaries were focused on determining "How much water is needed to provide a beneficial inflow?" where beneficial inflows are defined 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 and productivity of economically important and ecologically characteristic sport or commercial fish and shellfish species and estuarine life upon which such fish and shellfish are dependent."
Whereas Senate Bill 3 efforts focus on determining a "flow regime" that provides for a range of inflows necessary to maintain a sound ecological environment, these earlier efforts focused on determining the minimum amount of freshwater inflow needed to best satisfy a specified set of management constraints to ensure the desired salinity or nutrient needs of fisheries species and the minimum acceptable fisheries productivity levels.
Together, all of these efforts seek to provide for a sound natural environment which is essential not only for maintaining the quality of life enjoyed by Texans and future generations of Texans but also for maintaining a strong state economy. TWDB supports environmental flow efforts in Texas through technical, administrative, and funding assistance.