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In general, what is the current “state of the science” with regard to sediment transport and channel shape/formation effects !of construction and operation of major dams?! (e.g. Is this a well- studied, well-understood topic or more of an area of research where hypothesis formulation and data collection/evaluation are more recent?)
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Description, generalization, prediction, and metrics of downstream channel change: past work
• Description (case studies) – Cory (1913); Lawson (1924) … • Generalization – Stevens (1938); Lagasse (1980); Williams and Wolman (1984) • Prediction – Magnitude of incision • Komura and Simons (1967); Strand (1977) – Duration of adjustment process • Williams and Wolman (1984); Church (1995) after deVries (1975) • Metrics of Alteration – Flow alteration • Richter at al (1996); Poff at al (1997)
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4000 3
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1500 1.6 February 1946 2000 2 1000 1.4 S
500 1.2 1000 1.5 *
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0 1 * 0 1 October 1942 February -500 0.8 1942 November 1945 -1000 0.5 -1000 0.6 September 1949
STORAGE PER UNIT METERS DISTANCE, IN PER METER CUBIC -2000 0 STORAGE PER UNIT METERS DISTANCE, IN PER METER CUBIC CUMULATIVE REACH-AVERAGE VOLUMEIN SEDIMENT CHANGE CUMULATIVE REACH-AVERAGE
CUMULATIVE REACH-AVERAGE VOLUMEIN SEDIMENT CHANGE CUMULATIVE REACH-AVERAGE -1500 0.4 300 250 200 150 100 50 0 200 150 100 50 0 KILOMETERS DOWNSTREAM FROM PARKER DAM KILOMETERS DOWNSTREAM FROM HOOVER DAM
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Previous efforts to generalize about dam impacts • Williams and Wolman (1984) – Summarized channel change below 21 dams – Empirical relations for duration of degradation, degree of narrowing • Richter et al (1996); Magilligan et al. (2003, 2005); White et al. (2005) – Characterization of changes in flow regime • Brandt (2000a, 2000b, 2000c) – Identified 9 styles of change below dams – Predicted channel form • Grant et al. (2003) – Fractional change in duration of sediment transporting flows – Ratio of downstream sediment supply to upstream supply
Efforts to anticipate changes in channel form rely on generalizations about the water/sediment balance
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Sediment mass balance: shift towards deficit or surplus
Borland’s illustration of Lane’s (1955) concept, drawn by Vitaliano
Factors that induce degradation Factors that induce aggradation below dams: below dams: Reduced sediment supply Reduced floods or total stream flow Fining of sediment supply Coarsening of sediment supply
If there are comprehensive empirical studies, what are they showing?! I.e. how much and what kind of changes downstream; how far downstream are changes evident (i.e. ! the role of tributary contributions); what effects, if any, have been identified with respect to downstream health of aquatic and riparian habitats; what are the major determinative factors with respect to river type, reservoir operation and/or time within which “new equilibrium” is established? !
Are there any well accepted models for analyzing the above questions?!!
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Three Metrics
• Perturbation of the predam sediment mass balance – Assessing shifts towards deficit or surplus
• Likelihood of post-dam bed incision
• Potential for changes in width based on proportional change in annual floods
1 / Sediment Wild accumulation SUPPLY SUPPLY SUPPLY
0.1 SEDIMENT SEDIMENT SEDIMENT SEDIMENT
0.01
PRE-DAM PRE-DAM Sediment POST-DAM evacuation
0.001 0.01 0.1 1 POST-DAM 2-YEAR FLOOD / PRE-DAM 2-YEAR FLOOD
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T2P"&)P./<)K"<)"2/P.I.+"C;2/.2'"2#.&/&.*)(.2+"C;25/ /*.#<."&)2I/#'"22.3/#"K"#)+45/ /#<."C2I/"/K;&)CP./D..*B"#$/;D/.2'"2#.*/P. ]YK!S$ h$A)-00*5$0-223&'0a$2*.J5(*:$'0$'082*-.*.$'0$.(-a*$ hi1*2I-0?$:*D3.'H30$2*.J5(*:$'0$-::'H30-5$1*2H8-5$j33:D5-'0$-882*H30$ h$C*0.*$1*a*(-H30$'082*-.*.$.*:'4*0(-H30$ X."2/"2*/1#'()*+5/N?6?/ #S$ !"##"##$ Glen! Canyon Upper Colorado River Grand! Canyon! Are there any well accepted “rules of thumb” for the degree of alteration from historical flows with respect to preventing adverse effects of geomorphological/sediment transport changes? If so, !what studies support these “rules of thumb”? ##$ !"##"##$ 1+<"+.I).&/D; 0.1 Qs* bE$:*`8'($*,'.(.N$ 0.01 2*'0(23:J8*$Sediment .*:'4*0($Deficit Miniature River 0.001 0.1 1 Q* 1#'()*+/"2*/M)3#;#$5/N??O/ Sediment Floods needed needed; (2.9x post- (0.6x post- dam supply)$ dam flood)$ Sediment needed (1.2x post- Floods needed! dam supply)$ Sediment needed (0.9x post- dam supply)! Sediment needed (2.9x post-dam supply)! #K$ !"##"##$ +)*$83.(.$3E$-::'0a$.*:'4*0($E234$ k-?*$Q3&*55$'0(3$[2-0:$A-0;30$ $ P 9::'H30$3E$TBM$,$#S $La";2$I;$:2*:a'0a$-0:$ A. 80000 D'D*5'0*l$"KK<")&"3/3.P.3/#;&+/.&C("+.&$$ 1996 1996 high flow combined flow of upper 70000 experiment D7;$$E#>,>%7,.%#F&-&G*#9&.E*.#0*#H7%.#9&.E*.#I&<# Colorado, Green, and San Juan Rivers JKLLM#<,77,*.#'&>,0&7#'*)0)N#K!4!#<,77,*.#&..;&7#*>%$&8.2#60000 '*)0O# 50000 Lees Ferry D7;$$E#>,>%7,.%#F&-&G*#9&.E*.#0*#P%%)#Q%$$E#JKRSM#40000 <,77,*.#'&>,0&7#'*)0)N#K"T#<,77,*.#&..;&7#*>%$&8.2#'*)0O30000 # A. ! 20000 80000 1996 1996 high flow combined flow of upper 10000 70000 experiment Colorado, Green, and San Juan Rivers DISCHARGE, IN CUBIC FEET PER SECOND PER FEET CUBIC IN DISCHARGE, 60000 0 50000 Jul/1 Jan/1 Jan/1 Mar/1 Nov/1 Sep/1 May/1 Lees Ferry 40000 30000 20000 mTT$4'55'30";2$'.$/b7$*.H4-(*$3E$83.($2*:J8*:$ B. 10000 80000 SECOND PER FEET CUBIC IN DISCHARGE, Randle et al, 2007! $ 2004 jJ8(J-H0a$j3&. 0 70000 Jul/1 Jan/1 Jan/1 Mar/1 Nov/1 Sep/1 combined flow of upper May/1 60000 Colorado, Green, and San Juan Rivers 2004 high flow 50000 experiment Lees Ferry B. A. 80000 80000 40000 2004 1996 1996 high flow combined flow of upper 70000 70000 experiment Colorado, Green, and San Juan Rivers 30000 combined flow of upper 60000 60000 Colorado, Green, and San Juan Rivers 20000 2004 high flow 50000 50000 experiment Lees Ferry Lees Ferry 40000 10000 40000 30000 30000 0 20000 20000 Jul/1 Jan/1 Jan/1 Mar/1 Sep/1 Nov/1 10000 May/1 DISCHARGE, IN CUBIC FEET PER SECOND PER FEET CUBIC IN DISCHARGE, 10000 0 0 Jul/1 Jan/1 Jan/1 Mar/1 Nov/1 Sep/1 May/1 Jul/1 Jan/1 Jan/1 Mar/1 Sep/1 Nov/1 May/1 C. A30.(2-'0(.$30$ 80000B. 80000 2008 2004 2008 high flow 2*'0(23:J8'0a$85*-2d&-(*2$70000 70000 C. experiment80000 combined flow of upper 2008 j33:.$'0(3$-$.*:'4*0($60000 Colorado, Green, and San Juan Rivers 2008 high flow 60000 70000 experiment combined flow of :*`8'($.;.(*4$ 2004 high flow 50000 experiment upper Colorado, Green, Lees Ferry 60000 50000 and San Juancombined Rivers flow of 40000 upper Colorado, Green, 50000 and San Juan Rivers 30000 40000 40000 20000 30000 Lees Ferry 30000 Lees Ferry 10000 20000 20000 0 10000 Jul/1 DISCHARGE, IN CUBIC FEET PER SECOND PER FEET CUBIC IN DISCHARGE, Jan/1 Jan/1 Mar/1 Nov/1 Sep/1 May/1 10000 f-(J2-5$-0:$-8(J-5$k**.$6*22;$ SECOND PER FEET CUBIC IN DISCHARGE, 0 j3&.$$ 0 Jul/1 Jan/1 Jan/1 Mar/1 Nov/1 Sep/1 May/1 Jul/1 Jan/1 Jan/1 Mar/1 Nov/1 Sep/1 May/1 C. 80000 2008 2008 high flow 70000 experiment 60000 combined flow of upper Colorado, Green, 50000 and San Juan Rivers 40000 30000 Lees Ferry 20000 #M$ 10000 DISCHARGE, IN CUBIC FEET PER SECOND PER FEET CUBIC IN DISCHARGE, 0 Jul/1 Jan/1 Jan/1 Mar/1 Sep/1 Nov/1 May/1 !"##"##$ SEDIMENT-YEAR 2000 MASS-BALANCE SAND BUDGET BETWEEN LEES FERRY AND THE GRAND CANYON GAGE LEES FERRY GAGE (ft LEESFERRYGAGE 6.0 50,000 THE DISCHARGE AT L-'0(-'0'0a$D3.'H1*$4-..$ MASS-BALANCE UNCERTAINTY ENVELOPE 40,000 5.0 WATER DISCHARGE 30,000 I-5-08*$'.$1*2;$)-2:$ 4.0 20,000 3.0 10,000 3 /s) &'()3J($.*:'4*0($ 2.0 Sand budget negative for year 0 1.0 -Ja4*0(-H30$ ACCUMULATION 0.0 EROSION SAND MASS RELATIVE SAND IN TOREACH -1.0 THAT ON AUG 15, 1999 (million metric tons) THAT (million ON AUG 15, 1999 -2.0 Z;KK)2I5/ -3.0 \<)].2/ JUL 1999 JUL JAN JAN 2000 JUN 2000 JUN FEB 2000 SEP 1999 APR APR 2000 OCT 1999 DEC 1999 DEC AUG 1999 NOV 1999 MAY 2000 MAR MAR 2000 #;((-2%/ A30(2355*:$j33:.$UJ'8?5;$:*D5*(*$()*$ -1-'5-I5*$.JDD5;B$ #OOP$ KSS\$ ['"2I./)2/&-&K.2*.*/&.*)(.2+/ #;2#.2+<"C;2/\)+'/C(./*-<)2I/+\;/3" #T$