NonBasicSpecificComments04

• Title: Comments 4
• Date: 10/23/2003
• SWSI - Doc Type: Comments

February 2003 .

ECOLOGICALLY SUSTAINABLE WATER MANAGEMENT

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Box 1. Green Riv~r, If,entucky

Scientists frOl11 The Nature Conservancy are now worki*g with the U.S. Army Corps of EngIneers to
design n1odifications to dan'l operations on the Green RiverHn Kentucky to reduce their impact on natural
flow conditions and aquatic species. One of the richest aS$en1blages of native fish and mussels l11 NQrth
Alnerica is located downstreanl of the Green River Dam. ioperated by the Corps since 1963 to, provide
flood control and reservoir...based recreatJonal benefits. Substantial alterations to the river's natural flow
regime occur each year in the fall, when the Corps fJwitches from recreation Jake management to flood
conti.oL operatiol1s. Reservoir levels are maintained -at a hiJgh level during summer to accon1nlodate ree..
reationaI uses. During Septelnber and October, the water h!vel in the reservoi1. is quickly lowered by > 3
m to restore storage capacity needed to capture winter fio~ds. Releasing this la.rge volunle of water in a
short period of time .,produces greatly elevated flows that e~telld far downstreatn from the dam and disrupt
native biota" Aquatic scientists hypothesize that steady low ~ows are:needed in the fall season to concentrate
cel"tain prey sp.ecies, enablhlg the.ir predato~s .to feed mo~e efficiently. Certain mussels ar~ believed to
release larvae during the autumn season~ which may be dis:rup,ted by high fiows~ Other aquatic organisms
likely depend upon naturally quiescentt low..flow periods (or conserving energy prior to winter.
The collaborative efforts between the Corps and the Co~servancy are focused on shifting the timing of
lake leveL lowering (and associated increases in downstrea~ river .flows) from September-October to late
Novembe1; wh~n river flows would be naturally highe.t duling the Onset of the' wInter rainy seaso:n. B'ecause
the .lowering of reservoir levels will also be conducted over jan extended period~ .the daily re~ervoir releases
can be lessened. In addition to shifting the thning and incr~asing the duration. of the"reservoir draw-down~
the dam releases will be pulsed to coincide w~th storm e~ent.s rather than releasing at a constant .ratet
thereby minlicking some of the" river~s .natural patterns of }!adab!lity,_ '., _ .. ._
The basic ideas behlnd these operational changes were i:dentifted during an initial two-hour discussion.
between the scientists and ellgille~rs, This.. dialogue moved! quickly toward possible solutions because the
areas of potential incompatibility had been well de~cribe~ by Conservancy scientists; Corps engineers
shared the ,ConserVatlcy ~s goal of maintaining the tl ver ec;osystem in a heal thy cOl1dition; and they both
sought to restore ecological int~grity whlJe continuing to r:neet the operational purposes of the dam.
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Equipped with adequate data and shared me%lns for
assessing them~ water managers, scientists, conserva-
tionists; and water users should carefully examine each
area of potential incompatibility identified in Step 3
'and consider whether each ecosystem requil"e.ment and
human use might be met in a.lternative ways that would
relnove 01. reduce the conflict. SOll1e of the nlost pow-
e't:fuI nl,eans of resolving these conflicts involve chang..,
ing the timin'g or location of hun'1a11 l1ses toward greater
cOll1patibility with natural hydrologic cycles or the sea.
sonal or life cycle needs of native species. For instance,
can wator be captured for human use during a time of
the year fuat minimizes the relative change to the nat..
ural hydrograph and its ecological consequences? Can
the location of a water diversion be relocated .down-
streatn of critical fish spawning al.eas?
A growing number of i~1novative strategies are now.
being tested and put to use for the purpose of elimi-
nating conflicts between human ano.. ecosystem needs
for water (see Boxes 1 aud 2 for Green River, Kentucky
aud San Pedro River, Arizona). ,Datn operations are
being modified to reshape human-influenced l}ydro-,
graphs' i.nto son1ething more cOl'1?-patible with ecos'ystem
requirenlents .while stilllneeting the bU111an needs for
which they were originally designed (NaturnJ Resourc-
. es Law Center 1996). New technolog~es for water con-

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serv~tion Ln cities~.. industriesv and agriculture are re-
duci~g the volume of water needed to support human
end~avors, or eliminating the need to build additional
stor,ge xeservoirs that might nuiher h'1'l.pair natural by-
dro lp gic re gim es (Maddaus 1987) Po stet 1999, Oleick '
. 2000~ Vicker~ 2001}: MaJiy governmental entities are
adopting demand management strategies tllat place Ihl1-
its dn th.e amount of allowable water withdrawals from
cert~in - freshwater sources. Water Inarket transac tions,
incl'~dillg the purc~\ase of ir;rigation water~ rights. and
their' conversion to Uinstream .flow rights~' that allow
the :Water to remain in the 'river (Gillilan and Brown
199~), or paying fanners \lot to i1"rigate fields during
drought pe~tiods, hold pron]ise for keeping river flows'
frorP. dropping to cd ticaUy low le.ve1 s (Michel sen and
Yo~ng 19937 Wigington 2000)1 As new strategies sue..
cee~ and begin to be more widely cOl~1~unicated to
,watbr l\1anagers and conservationists~ we expect the
J
propabilities for attaining ecologically sustainable wa-
tet tnanagement in the world1s river basins to improv,e
C01'l:~ iderab ly" .
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STEP 5: CONDU-CTING W ATBR
MANAGEMENT EXPERtMBNTS

J?uring each of ,the prece_ding steps) a .number of
ungertainties abO\Lt ecosystem flow requirelnents or h1.'L-

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