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<br />.~ oil · <br />., <br /> <br />.. <br /> <br />Eca/ngi,'n.l Applklllimts. ~ 3l J), 2003 I pp. 206-224 <br />e 2od3 by the SCQ[ogica! Society of America <br /> <br />ECOLOGICALLY SUSTAIN'ABLE WATER MANAGEMENT; <br />MANAGING RIVER FLOWS FOR ECOLOGICAL INTEGRITY <br /> <br />BRIAN D. RICHTER, E.5 RUTH MATHEWS~2 DAVID L. HARRrSON,3 AND ROBERT WrOlNGTON4 <br /> <br />e The Nature Conservancy, 490 Westfield Road. Charlottesville, Virginia 22901 USA, <br />2The Nature Cons erva.n cy, 410 North 4th Street. Ml. Vernon, .Washlngtotz 98273 USA <br />3Moses, Wittenlver. Harrison. and Woodruff: P. O. Box 14401 Boulder~ Colorado 80306..1440 USA <br />. 4The Nat;tre Conservancy, 2060 Broadway. Suite 230, Boulder. Colorado. 80302 USA <br /> <br />Abstract. Human demands on the wodd's available freshwater supplies continue ,to <br />grow as the global population increases. In the endeavor to manage water tQ meet human <br />needs, the need,s of fr~shwater species and ecosysteln~ have largely been neglected, and <br />the ecological consequences have been tragic. Healthy fxeshwater ecosystems provide a <br />:weatth of goods and services for soc~ety, but our appropriation of fi.eshwater flows must <br />be better'lnanaged if we hope. to sustain these benefits and freshwater biodiversity~ We <br />offer a. framework for developing an ecologically sustainable water management program~ <br />in which human needs for water are met by storing and diverting ,"vater in a man,ner that <br />can sustain or restore the ecological integrity of affected river ecosystems. Our six-step <br />pl'ocess includes: (I) de.ye(oping initial numerical estimates of key aspects of river flow <br />necessal'Y to sustain nativ~ species and natural ecosystem functions; (2) accounting, for- <br />human uses of water, both cyrrent and future, through development of a computerized <br />hydrologic simulation model that facilitates examillation of hunlan...induced alterations to <br />river flow regimes; (3) assessing incompatibilities ljetween human and ecosystem needs <br />with p8rticular attention to their spatial and te.nlporaI cha.racter; (4) collaboratively searching <br />far solutions to resolve incompatibilities; (5) conducting water management experiments <br />to resolve critical.'uncel'ta.inties that frustrate efforts to integrate human and ecosystem <br />needs; and (6) designing and bIlplementing an adaptive. management program to facilitate <br />ecologically su~tainable water n1anagelnent for the long term. Drawing fi.om case studies <br />around the world to illustra.te our framework, we suggest that ecologically sustainable water <br />111Qtl3gE:lnent is . attainable in t~e vast 1'najotity of the world IS tiver basins4 Howeve:r, this <br />quest will become far less feasible jf we wait until water supplies are further over-appro- <br />priated~. <br /> <br />Key words:. adaptive lnanagement; biodiversity; dan-l op-el'ations.. ecological flow assessment; <br />ecosysttm management; ecoS)lstem monitoring,~freshwatel' ecosystems}' hydrologiC alteration; instl"f!cl1n <br />jlOl-I'; river management." 3llSfc1illable ....Fater developnrent~. l1;afer r'eSOUl.ceS management. . <br /> <br />it is one thing to find fault with an existing system. <br />It is another thing altog~ther~ a more difficult task, <br />to replace it with another approach that is better. <br /> <br />-Nelson Mandela, 16 Novelnber 2000 <br />(spealdng of water resource ma1?-agement) <br /> <br />In I11any areas 'of the wOl'ld, growing human popu- <br />lations are rapidly depleting available freshwater sup.. <br />plies. During the 20th century, the gLobal human pop.. <br />ulation increased fourfold to more than six billion (6 <br />X '109). Water withdrawn from natural freshwater eco. <br />systems increased eightfold during the saln~ period <br />(Gleick' I998)L Facing an 0111LnOllS specter of increas.. <br />ingly severe \vater..supply shortages in many areas of <br />the world, social planners and government leaders are' <br />exploring strategies for managing' water resources StlS- <br />tainably (IUC~ 2000). This quest for sustainabiHty typ- <br /> <br />MaJluscri pt received 26 $eptelnber 2001; rev~sed 12 AprH <br />20Q2~ accepted 22 April 2002; final versLoJ'l received 31 May <br />2002, Corresponding Editor: J. S. Baron. ' <br />S E"Lnnil: brichter@tnc.arg <br /> <br />icaIly centers on managing hunlan uses of water such <br />that enough water of su~ficient quality is available .fo~ <br />use by future generations. <br />111 the, endeavor to manage water to meet various <br />hUlnan needs, however, the water needs of freshwater <br />species and ecosystelDs .have been largely neglect~d. <br />The ecological consequences have been tragic (IUCN <br />2000, Plingie et at. 2000, Stein et at. 2000., Baron. et <br />a1. 2002). The alteration of river flow regimes .asso- <br />ciated' with dam qperations has been identified as one <br />of three leading causes, along with nOllpoint source <br />polJution and invasive species) of the if!lpelihn~nt of <br />aquatic animals, (Richter et at. 19970, Pringle et aI. <br />2000). Freshwater ecosystem services alld products <br />valued by society have been severely comproll1ised as <br />well (Postel and Carpenter 1997; IUCN 2000). ' <br />The water needs of hun1ans and natural ecosystelns <br />are COlllulonly viewed as cOlnpeting with each other. <br />. Certainly, there are lin1its to the arnount of water t{1at <br />can be withdrawn fron1 freshwater systenlS before their <br />natilral fllnctioning and pl'oductivity~ native species} <br /> <br />206 <br />