Environmental Flow

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					 Environmental Flow
Science, Policy, and Implementation

                         Eric S. Hersh
                      January 31, 2008
 environmental flow definition
                               Brisbane Declaration 2007

“The quantity, timing, and quality of water flows
required to sustain freshwater and estuarine
ecosystems and the human livelihoods and well-
being that depend on these ecosystems”
Ecological functions (goods and services)
   Fish and wildlife: habitat, migration, reproduction, biodiversity
   Endangered species protection
   Fisheries (commercial and recreational)
   Navigation
   Hydropower
   Recreation
   Waste assimilation
   Water supply
   Food supply
   Flood and drought mitigation
   Nutrient delivery
   Sediment transport
   Coastal salinity regulation
   Aesthetics
         interdisciplinary nature
   Engineering: hydrology, hydraulics, water quality
   Biology and ecology
   Geomorphology and physical processes
   Policy and regulation
          transboundary nature
   Basin-wide management scale
   Transboundary difficulties in prescribing and
    regulating environmental flow needs
   Disparities in water availability and need,
    infrastructure, technical capacity, environmental
    awareness, regulatory structure
human impact
                 human impact
   Artificial higher or lower low flows
   Erratic daily flows from hydropower demand
   Prevent or minimize floods
   Disconnect floodplain
   Channelize rivers and alter habitat
   Eliminate variability
Guadalupe Rv abv
Comal Rv at New
 Braunfels, Daily
 Maximum Flow

 Trinity Rv nr
 Rosser, Daily
Minimum Flow
historic river resource protection
   Water quality
       U.S. Clean Water Act, 1972
       Designated uses, water quality criteria
       “The objective of this Act is to restore and maintain the
        chemical, physical, and biological integrity of the
        Nation’s waters”
   Water quantity
       Minimum flow (flat line)
       “…nothing in this Act shall be construed to supersede
        or abrogate rights to quantities of water which have
        been established by any State.”
       flow- “the master variable”
   Controlling factor in riverine
    physical, biological, and
    chemical processes
   e.g.: water temperature,
    dissolved oxygen, available
    habitat, spawning cues, channel
    shape, substrate type
Question: manage flow for…?
                 Answer: everyone.
               the natural flow regime
                                   Poff et al 1997

(Postel and Richter, 2003)
the natural flow regime

                                   Not depicted:
                         Rate of
 Magnitude               Change


the big question…

    How much water does
        a river need?
                             water allocation
                                         20th century

Ecosystem support allocation
                                         21st century

                                         what is this
(Postel and Richter, 2003)
                Texas: Legislation
   Senate Bill 2 (2001): the science bill
       Establish and maintain an instream flow data collection
        and evaluation program
       Develop methodologies to determine flow conditions in
        Texas rivers and streams necessary to support a
        sound ecological environment

   Senate Bill 3 (2007): the implementation bill
       Establishes the who, when, and how of environmental
        flow implementation in Texas
       TCEQ must adopt the recommended standards by
        September 1, 2010
                     Texas: Methods
   Lyons Method (Bounds and Lyons 1979)
       Used in permitting
       Based on a percentage of monthly median flow
         • Oct to Feb: 40%
         • Mar to Sept: 60%

   Consensus Criteria for Env Flow Needs (CCEFN)
    (TCEQ 1997)
       Used in planning
       Percentage of monthly naturalized flow from WAM
         • Nat Q > median Q  protect median Q
         • 25th %ile < Nat Q < med Q  protect 25th %ile
         • 25th %ile > Nat Q  protect 7Q2
flow components
             NRC 2005

11 rivers
26 dams
13 states
Savannah River Basin
           Richter et al 2006
example flow prescription
              European Union
 Water    Framework Directive (2000)
     Classify ecological status of water bodies
       • High, good, moderate, poor, bad
     Measures to prevent deterioration and work
      toward at least a ‘good’ status
     Each country legislates, implements
                  South Africa
 Timetable
     1994 – end of apartheid
     1996 – constitution signed
     1998 – National Water Act
 Water   reserve = ecology + basic human need
     Phase I - ~20% of flow for ecology + 20 LPCD
     Phase II – Building Block Methodology
 Driestinhabited continent; most dams/capita
 Water Reform Framework (1994)
     Sustainable use and protection of freshwater
 Env Flow limit defined as point where
 additional change results in an increased risk
 of unacceptable degradation
           Murray-Darling Basin
 Water   cap (1997)
     Capped to 1993/4 levels
     Adjusted for climate
     Allows for trading
   Adaptive management
       “learn by doing” process
   Water rights management
       Procurement and retirement of existing
        consumptive-use permits via banking and
        trust systems
 Dam removal
 Dam reoperation
      questions for discussion
How much water does a river need? Can this
  really be determined? How?

What tools can be used to demonstrate the need
  for and value of environmental flows?

What instruments can be used to implement
  environmental flow prescriptions?

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