WSP09733

• File Number: 8443.400
• Description: Narrows Unit - Reports
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 2/1/1978
• Author: US DoI BoR
• Title: Supporting Data for Special Report Investigation of Review Issues Narrows Unit Colorado part 2 of 3
• Water Supply Pro - Doc Type: Report/Study

~

.

-
~
~

.

J~~~
OO~0

River Diversion Requirements

If only the amount of water needed to satisfy the annual farm
delivery demand was recharged at the beginning of the irrigation season,
overdrafts on the ground-water system would occur. The reason for the

overdrafts is that the recharged water will not be immediately pumped,

but will be pumped at a varying rate throughout the irrigation season

with maximum pumpage anticipated to occur in July and August. Due to

this lag time, drain-out of a portion of the recharged water will occur.

Assuming homogeneous and isotropic aquifer characteristics between the

recharge area and the stream, the amount of drain-out occurring in a

given time frame depends largely upon the distance between the stream
and the recharge ponds.

The USGS has done considerable research regarding this concept in

the South Platte River Valley (Jenkins, 1968a, 1968b, 1970; Moulder and

Jenkins, 1969; Jenkins and Taylor, 1974.) This work has resulted in the

publication of a series of maps (Hurr, et a1., 1972) showing what has

been termed lines of equa1-stream-dep1etion factor for the alluvial

aquifer of the South Platte River Valley. In general, these maps give

an idea of ho" long it would take for given stresses (recharge or pumpage)

occurring at various distances from the river to be felt by the river.

The stream depletion factor represents the amount of time it would take

for 28 percent of the stress to be felt by the river. The USGS has gone

further (Ted Hurr and Alan Burns, personal communication) and developed

a series of curves based on the stream depletion factor concept that

give the percent of accretion or depletion to streamflow due to stresses