The Science Of Instream Flows

Across the United States, municipalities, counties, and states grapple with issues of ensuring adequate amounts of water in times of high demand and low supply. Instream flow programs aim to balance ecosystem requirements and human uses of water, and try to determine how much water should be in rivers. With its range of river and ecosystem conditions, growing population, and high demands on water, Texas is representative of instream flow challenges across the United States, and its instream flow program may be a model for other jurisdictions. Three state agenciesâ€"the Texas Water Development Board (TWDB), the Texas Parks and Wildlife Department (TPWD), and the Texas Commission on Environmental Quality (TCEQ)â€"asked a committee of the National Research Council (NRC) to review the Programmatic Work Plan (PWP) and Technical Overview Document (TOD) that outline the state's instream flow initiative. The committee suggested several changes to the proposed plan, such as establishing clearer goals, modifying the flow chart that outlines the necessary steps for conducting an instream flow study, and provide better linkages between individual studies of biology, hydrology and hydraulics, physical processes, and water quality.

Across the United States, municipalities, counties, and states grapple with issues of ensuring adequate amounts of water in times of high demand and low supply. Instream flow programs aim to balance ecosystem requirements and human uses of water, and try to determine how much water should be in rivers. With its range of river and ecosystem conditions, growing population, and high demands on water, Texas is representative of instream flow challenges across the United States, and its instream flow program may be a model for other jurisdictions. Three state agenciesa "the Texas Water Development Board (TWDB), the Texas Parks and Wildlife Department (TPWD), and the Texas Commission on Environmental Quality (TCEQ)a "asked a committee of the National Research Council (NRC) to review the Programmatic Work Plan (PWP) and Technical Overview Document (TOD) that outline the statea s instream flow initiative. The committee suggested several changes to the proposed plan, such as establishing clearer goals, modifying the flow chart that outlines the necessary steps for conducting an instream flow study, and provide better linkages between individual studies of biology, hydrology and hydraulics, physical processes, and water quality."

"[This book] presents the collective views and recommendations of the Instream Flow Council's (IFC) state and provincial fishery and wildlife agency members regarding appropriate instream flow strategies for managing, maintaining, or restoring riverine fishery and aquatic wildlife resources and processes. [It] also identif[ies] eight components that should serve as guidelines in establishing or improving existing agency instream flow programs and in developing prescriptions to be addressed in each instream flow assessment. These components include hydrology, geomorphology, biology, water quality, and connectivity as well as legal, institutional, and public involvement."--Page xxv.

Flows of the Columbia River, although modified substantially during the twentieth century, still vary considerably between seasons and between years. Lowest flows tend to occur during summer months when demand for irrigation water is at its highest and when water temperatures are greatest. These periods of low flows, high demand, and high temperature are critical periods for juvenile salmon migrating downstream through the Columbia River hydropower system. Although impacts on salmon of any individual water withdrawal may be small, the cumulative effects of numerous withdrawals will affect Columbia River flows and would pose increased risks to salmon survival. The body of scientific knowledge explaining salmon migratory behavior and physiology is substantial, but imperfect, and decision makers should acknowledge this and be willing to take action in the face of uncertainties. In order to provide a more comprehensive water permitting process, the State of Washington, Canada, other basin states, and tribal groups should establish a basin-wide forum to consider future water withdrawal application permits. If the State of Washington issues additional permits for water withdrawals from the Columbia River, those permits should contain provisions that allow withdrawals to be curtailed during critical high-demand periods.

The need to address instream flow needs (IFN) in the Northern River Basins Study arises primarily from issues related to flow regulation on the Peace River. Flow regulation may have effects on fish habitats and has clearly affected riparian habitats in the study area. This report presents proceedings of a workshop held to review methods and approaches for conducting IFN analyses, to consider their applicability to the northern river basins, and to develop recommendations for undertaking IFN investigations as part of the Study. The workshop included two sessions, one on IFN related to fisheries and aquatic habitats and one on IFN related to riparian and delta habitats. Topics of presentations and papers include river hydrology, water quality considerations, vegetation studies, instream flow assessment, winter habitat, implications of river impoundment, modelling of wildlife habitat, channel morphology, sediment transport, and wetland vegetation management.