PUB00006

• Year: 2005
• Title: Colorado's Historic Water Projects
• CWCB Section: Administration
• Author: Applegate Group, Inc
• Description: A calender with pictures and descriptions of historic water projects.
• Publications - Doc Type: Historical

GROV"Dlf:~lER Ja.-wt:sa TUfF. A.\D RECfU/lGF. Ta{pF.R~nRE Em.\um OF THE DE\l"ER A.\VAI/.-tP..vfOE AQl1Ffk>, DE.\lTR /liSL\, COLORADO

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0 5 10 15 20 25 30 35
Timefka}

Figure 2. Recharge temperature of groundwater ~mples (solid
squares) and uncertainty (error narsl, Denver and Arilpilhoe
aquifers, Denver Basin, Colorildo, and glacial and Holocene tem-
perature estimates (dashed lines) reconstructed from mean annudl
modern temperature (solid diamond) and glacial ternper.1ture
depression of SSe.

Samples from wells farther toward the cenler of the ba~in.
regardless of aquifer, have apparent rt'"~idence times of
22,000-24,CXXJ years. The sa.mple from The Pinery (PIN-02)
.~howt'd an e~timated residence time of gre;lter than 30,ono
years. but there were some prohkm~ a.,..,udated with the
analysis of this ~ample. In a qualit.lIive ~n~c. the apparent
residence times art' wh;1l would be expened, with the
younger water toward the outcrops (R"charge area) and
the okkr waters in the middle of tht' basin.

F~"itimatro PaJeotemperalUrt."'!'

The estim:lll.->d temper.llures at the time of recharge are
shown in Table 4 They range from 1.5 to 9.irc. nle 1..1
values of all s3mpk.. were lx'low or very nl~.lr j.8.i, the
kvel of 95% probahility for the modd. Tht'~t' rt:"Sult~ ~llH-
gest that the me3n elt'vation<.; u.<.;('d 3re reasonable, that me
exces....-air ('omponent of the ....3mpks is not fr,K1ion;lted,
and the estimated recharge tempt'r.ltures are fl.-'a.sonahle.
The uncenaimy in derin:"C1 redurgt..' temper.Hurl." rl'<.;ulting
from Ihe level of inslmment precision \u:-- caku\att'd :I."
0.9'C C\13nning and Solomon, 200},. }kcakubtinK
rech3rge temperature with minimum and maximum I;'kva~
tion... was used to estimate um:l'naimy in redlarge tempt'r~
atur!;" resulting from Ihe assumplion of rt"t.:harge elevation
(T3ble .n. Tht..' sum of Ihese \\'a.... lISl.-oJ to approximate {he
total unn.'Tt.1.inty in redlarge leffipt-'r:llure in this study,
Recharge k'mperatures and uTKert3imks werl' ploned
with estimates of modern and gbci:ll tl'mperalures (Fig, 2).
The S3mple from Donab (DO:'-J-04) j,<.; wry dos\:." to thl'
modem lemperatlln.: in the fl.-'('harge ;trea as would be pre-
dicteti by 3 residem'l.-' timt' thaI is younger than the end of
the last g1adal period. The recbarg\:." k'mper,Hures of tilt"
mher s3mples :lre 311 lower than thl.-' modt.'m {emlwr.lIure,
The re..idence time." :100 lower rt..'charge temper.ltur\:."s of
Ihe.'>C samples ~uAAe...t th\:."Sl' were rechar~t'd during Ihe 1:1"t
gbcial period. S3mples PARK-01 amI AL'R..{)7 havt'
recharge temperatures that art' significantly grl':Her than
the estimated glacial tcmpcralllre. This t'ould reflect signifi-
cam tl.'mpcr3ture IluchJ3lion.. within Ihe gbdal period,
mixing of Hol(Kenl' Kfoundw:ller and'or lhe dillllion of
He activity th3t 11l3ke... lhe gruunowatt,:r 3ppear 'old: The
Lltler explanation ,"llggesb Ihal residence times could he as
YOllng :IS the t'nd of the Iasl glacial period, <lpproxim.J.tcly
12 ka in Colorado, \'(11ik confined conJitions are observed

Table 3,
laboratory analysis results and field measurements of groundwater conditions; He reported in percent modern carbon (pmC);
relative HC/ne reported as delta 13-carbon per mil VPDB (olle %oj; IOIilI dissolwd gas pressure (Pl[x,J.

Field
Rel.llive Gas Concentrations DIC Measuremenls
28N1 ]102 "OAr ~K, lONe 'H. 'H. "C bIle T PTDG
Sample Aquifer 10' ,0-' ,0-' ,0-' lO's 10.11 ,.,.. (pmCl 1%.) rCI [alml
DQN-04 Arapahoe 0.95 5.]8 1.05 6.98 2.05 0.89 0,1& ]].] -13.0 15.5 0.908
PIN-02 Arap.ahoe 0.99 0.55 1.15 8.49 1.52 1.92 1.5] <2.27 .12.7 22.4 1.119
PARK-Ol Arapahoe 0.97 192.01 1.08 8.00 1.72 ].19 1.11 4.59 -13.0 28.7 1.155
AUR-08 Arapahoe 1.00 3,55 1.14 8.44 0.97 513 2,33 5.&0 -10./! 30.2 1.122
PARK.O] Denver 0.99 0.27 1.07 7.69 1.57 1.65 5.13 ..\.57 -13.2 29.7 1.050
AUR-07 Denver 0.86 ].46 0.95 6.67 0.86 O.B] 2.71 5.00 -9.7 17.9 1.012

165

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