HydrologyWellAugmentationInSP

• File Number: 8420.500
• Description: South Platte River Basin Task Force
• State: CO
• Basin: South Platte
• Date: 8/1/2007
• Author: Charles F. Leaf
• Title: Review Draft Report Submitted to SPTF
• Water Supply Pro - Doc Type: Report/Study

between Kersey is less than 15 percent of the
lagged consumptive use from total well pump-
ing (-31,400 af/yr vs. -248,000 aflyr)3) or 7 per-
cent of total pumping. Assuming 8,850,000 af
of alluvial aquifer storage, the hydrologic im-
pact ofthe wells is a 0.3 percent of total storage.

2. Well pumping has had virtually no impact on
the river during the months of November through
April.

FREQUENCY ANALYSIS

Because a wide year-to-year variation exists in replace- ~
ment requirements, a frequency analysis was made of ~
J: -50
the annual totals in Table 1. Results from this analysis ~
B
are plotted in Figure 7. Also plotted for reference are
hydrologic impacts of the simulated wells in 2002, the
most recent severely dry year, and also for 1935, as-
suming that all wells that existed in 2002 had pumped.
As seen in Figure 6, 2002 had a recurrence interval of
10 years and 1935 approximately 20 years. Also plot-
ted in Figure 7 is the level of replacement water well
users would be required to have in place each year in
order to continue pumping at historic levels. This in-
formation was obtained from a survey of court-decreed
replacement water requirements which indicated that
for some 4,000 wells that existed in 2002, almost

Figure 5 - Average Year Water Yield Simulation
of the South Platte River Between Kersey
and Julesburg 1975 - 1994

~

South Platte
River at Kersey

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...... ............South Platte River at Julesburg

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250,000 af of groundwater consumptive use would have
been required each year to pump at historic levels (Fig-
ure 8). Augmentation plans for the approximately 2,000
wells currently pumping, require a 50-year recurrence
interval supply of water to be in place each year for
these wells to pump at historic levels.

Figure 6 - Comparison of Simulated Average Annual Replacement Water Requirements for 1975 - 1994
With Total Groundwater Consumptive Use (GWCU)

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N D J F M A M J J A S

3) It is interesting that Glover (1975) proposed a restoration flow of 28,300 af in his analysis for 1957.

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