Laserfiche WebLink
<br />90 <br /> <br />ECOLOGICALLY SUSTAIN.ABLE "1AT.ER MANAGErv1ENT <br /> <br />213 <br /> <br />February 200~ <br /> <br />80 <br />a <br />of. 70 <br />! <br />~60 <br />~ <br />~ 50 <br /> <br />~ 40 <br />..J <br />0: 30 <br />:>> <br />~ 20 <br />::J <br />Z <br />10 <br /> <br />Potentlal rncom patl.blUtles <br /> <br />~ <br /> <br />. Ecosystem L1mit <br />1 ! <br /> <br /> <br /> <br />................. I- ...,. .... ,.. ..". ...,. ....., ... ..... ~... ...... ,.. ...., ........ ~.. I ..,. <br /> <br /> <br />o <br />1939 <br /> <br />1949 <br /> <br />1959 <br /> <br /> <br />1Q69" <br /> <br />1989 <br /> <br />. 1979 <br /> <br />FLG. 5. A hydrolpgic sinnll~tion Inodel developed for the ApalaQhicola.-Chatta.hoochee...Flint (ACF) River basin enabled <br />negodators to assess the influence of pl'ojected increases in human water uses and proposed dam operations on the flow <br />regime of the Apalachicola River in Florida. Fifty-five years of simylated daily flows were generated, One ,of the ecosY:Jteln <br />flow requirements for the Apalachicola River specifies that critically tow flows (<] 55 mJ/s) should not occur more than 24 <br />d in any year." Modeling results suggest that incolnpatibiUties between humal1 denlan.ds and thi.s ecosystem flow requirement <br />would occur in 6 of the S5 yr under the JaiHr~TY 2002 FJorida proEosal (gray bars). This ecosystem flow requirement was <br />exceeded in four years under histori~"al :ftow conditions. (black bars)_. <br /> <br />river ecosysteln.' Rather. scientists should be able to <br />provide blitial estimates. of ecos.ystem flow requ~re~ <br />ments that need to be sl1bseq ltently tested and'refined, <br />as described later. <br /> <br />STEP 2: DETERM1N(NG HUMAN INFLUBNCES ON THE <br />. FLOW REGIME <br /> <br />Humans use water for luyrfad'purposes including IUU" <br />nicipal and industtial water sLlpply, agric~tltural irriga- <br />tion1 hydroe lect.dc power generation, waste ass Lmilation, <br />navigatiol1, and recrea tion~ These hUl11an uses necessar- <br />ily modify the natural flow of rivets. Assessments of the <br />nature) degree, and location of humE!-u irifluences on nat.. <br />ural flow ' regimes should be perfonned for both cun~ent <br />and projected levels of human use, and expressed in <br />spadal and telnporal ternlS that' are co.nsistent with the <br />definition of ecosystem flow requirements. . <br />1-lydrologic sLmulation lnodeling has advanced r~pidly <br />and COll1putel'ized models have become essential tools <br />for understanding h.uman influences on river flows and. <br />desjgning ecologically sustainable: water lnanagemellt <br />approaches. Such Inodels are capable of performing si.. <br />multaoeous caLcula.tions of all the m~ny influences on <br />water flows, ev'en in complex river systems; They can" <br />be used to evaluate river flow changes ex.pected ,undel' <br />proposed water management approaches, ,such as in- <br />creased" future human delllands and associated operation <br />of water infrastructure. Because short-tenn hydl.ologic <br />conditions such as extreme low flows or flood;s can have <br />tremendous ecological influence, it is highly desirable <br />and increasingly feasible to develop hydrologic simu- <br />lation models that operate on daily (or shorter) tilne <br /> <br />step$. Daily flow hydrographs resl1lting f~om various t <br />leve)s .and types of human use can be generated for <br />pa:t1icular locations, enabling both visual and statistical _ <br />comparisons between flows required for eco~ystenl sup- <br />portj and human..altered flows (Figs. 5 and 6). <br /> <br />STEP 3: IDE~TIF'~ING INCOMPATIBIL1TTES B&TWEEN <br />HUMAN A.ND ECOSYSTBM NEBO.S <br /> <br />Ateas of potential incompatibility in water manage- <br />me~t can be identified by comparing ecosystem flow <br />req~h.ements (Step 1) with the flow regime r.esulting <br />frOt\1. meeting human needs (Step 2). These areas of <br />i.nc~lnpatibiUty ~ecome the point of origin for discus.. <br />sio~s in Step 4 (e.g.! Figs. 5 and 6). When these in.. <br />con;patibilities between human needs and ecosystem <br />requiren'1ents are well defined. efforts can be most ef- <br />fectively focused towatd resolving them. . <br />Ateas of potential incompatibility must be exarnined <br />both within and alno'ng years. .Within-year evaluations <br />wHi reveal the specific months or seasons during which <br />eco~ystem fl~w requirements are likely not to be lnet. <br />Ev~luations oflnultiple years will facilitate understand.. <br />ing I of the frequency with which ecosystem require- <br />me~ts could be violated (Fig. 5). Areas of potential <br />incQrnpatibiIity between human and ecosystem needs <br />sho~ld .also be evaluated for each liver rea.ch of con- <br />cer~, as the nature and degree of conflict can vary <br />,wi4ely from upstream to downstream) ~1' .act..oss a wa.. <br />ter~hed. Using models to explore water management <br />alternatives can identify discrete pinch pohlts and high.. <br />ligtlt the lnarginal differences be~ween altenlatives) <br />thet'eby constraining the scope of the conflict (Carver <br /> <br />j <br />