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<br />
<br />A single or occasional low flow event may not have lasting impacts. However, two
<br />or more consecutive years of low-flows are more likely to impact the aquatic community
<br />(carrying capacity) than a single low flow year. Both 1998 and 1999 followed years that had
<br />a 40-Day minimum of over 250 cfs, In 2000, flow had not been below a 250 cfs 40-Day
<br />minimum lor three consecutive years. 200 I was a second consecutive low-flow year. 2002
<br />was the third and most dramatic low-flow year of this dry period (Figure 6). In spite ofa
<br />high peak flow, 2003 was the fourth poor base flow year in a row.
<br />
<br />Colorado River (Palisade Gagel
<br />
<br />Pitlick (1999) detennined bankfull flow to be near 22,000 cfs for the 15-Mile Reach.
<br />The median annual peak flow for the 13-year Palisade Gage history was 13,500 cIs, The
<br />annual peak in \ 999 was 12,700 cfs and \ 3,500 cis in 2000, In 200 \ the annual peak was
<br />8,410 cis. It was only 2,780 cfs in 2002. The annual peak in 2003 was the highest of this
<br />five-year period at 20,300 cfs (Figure 7).
<br />
<br />Annual minimum flows recorded at the Palisade Gage for 1997, 1998, 1999, 2000,
<br />2001,2002 and 2003 were 1,710 cfs, 980 cfs, 435 cIs, 543 cis, 477 cfs, 58 cfs and 209 cis
<br />respectively. The 13-year median (50% exceedence flow) minimum flow was 550 cfs
<br />(Figure 8), The 40-day low-flow from the Palisade Gage for 1997, 1998, 1999, 2000, 200 I,
<br />2002 and 2003 were 2,090 cfs, 1,370 cfs, 1,470 cfs, 827 cfs, 779 cfs, 99 cfs and 619 cfs
<br />respectively.
<br />
<br />25000
<br />
<br />---I
<br />
<br />1997 -
<br />16,400 cra
<br />
<br />Annual peak lows, Maybell gage, 1917 10 2003.
<br />
<br />i
<br />u
<br />;;15000
<br />.x
<br />..
<br />"
<br />0..
<br />..
<br />~10000
<br />c:
<br /><(
<br />
<br />2003.
<br />12,900
<br />
<br />1999.
<br />9.980eb
<br />
<br />-
<br />I
<br />
<br />20000
<br />
<br />
<br />1998.
<br />10,400 era 2000.
<br />9.830cfs
<br />
<br />2001.
<br />7,650 cis
<br />
<br />5000
<br />
<br />9,930 cis
<br />Median
<br />
<br />,
<br />I
<br />2002 ~
<br />I
<br />3,420:
<br />
<br />o
<br />o
<br />
<br />0.1
<br />
<br />0.2
<br />
<br />0,3 0.4 0,5 0,6 0,7
<br />Exceedence Frequency
<br />
<br />0,8
<br />
<br />0,9
<br />
<br />1
<br />
<br />Figure 5. Exceedence frequency curve for annual peak flows at Ihe Maybell Gage, Yarnpa
<br />River.
<br />
<br />9
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