Lower South Platte River Study

• Contractor Name: Colorado Water Conservation Board
• Loan Projects - Doc Type: Feasibility Study

' Lower South Platte River Study
Colorado Water Conservation Board
December 2001
organization that assists well users to acquire and manage water supplies for well
' augmentation. GASP's purpose is to appropriate, buy,manage, own, and lease water rights
that can be released to the South Platte River to replace any out-of-priority depletions
occurring due to member wells pumping, to assure that no injury occurs to senior
' appropriators. Wells covered by GASP total over 3,000 along the South Platte River from
Fairplay to Julesburg.
' The LSPWCD operates in a similar manner and also to replace any depletions that may be
occurring due to member wells pumping when South Platte River flows are below 120 cfs at
' the state line.
Entities such as GASP and LSPWCD acquire and provide augmentation supplies to well
owners needing augmentation water. The amount and timing of augmentation for a
particular well depend on established stream depletion factors (SDFs). GASP, the LSPWCD,
and the NCWCD are assisting well users to develop recharge sites at appropriate locations to
facilitate effective well augmentation programs.
' The interconnection between surface water and groundwater in the South Platte Basin is
recognized and is part of the administration and management of surface water in District 64
of Water Division 1 (South Platte River Basin). The influence of groundwater withdrawals
' and recharge projects on stream flows in the Lower South Platte River is currently estimated
using the concept of Stream Depletion Factor(SDF) that was published in 1972 by the U.S.
Geological Survey(USGS) in an open file report (prepared by R.T. Hurr and P.A. Schneider,
et al.)on"Hydrogeologic Characteristics of the Valley-Fill Aquifer in the Julesburg Reach of
the South Platte River Valley, Colorado." Maps showing SDF contours have been published
' by USGS and are used to estimate the time taken for pumpage from a well to impact flows in
the river.
' The direct linkage between surface water and groundwater in the valley-fill aquifer has
resulted in the need for well pumping to be replaced to the extent that subsequent depletions
impact senior water rights. In addition to acquiring augmentation supplies, water users in the
' Lower Valley are developing recharge projects. Typically, these are shallow basins where
water that is legally and physically available is temporarily stored in the aquifer. This stored
' water returns to the river by gravity, either as a new source or an alternative source of water
for augmenting flows in the river and/or offsetting the effects of well pumping.
One potential use for a water project along the Lower South Platte River could be water for
augmentation and/or during a Compact call on the river. A storage project also is likely to
provide some degree of recharge through reservoir seepage and through seepage from canals
' that would carry more water than they have historically to fill the new storage space.
Augmentation benefits were considered in the reconnaissance study; however, evaluation of
GEI Consultants, Inc. 2-3 01002 Dec 2001 Lower South Platte River Study