LPPD000265

• Contract/PO #: C153756
• Contractor Name: Lower Arkansas Water Management Association
• Contract Type: Loan
• Water District: 67
• County: Prowers
• Bill Number: SB 96-124
• Loan Projects - Doc Type: Feasibility Study

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1. Fairly distribute its water resources and the risk ofreduced water availability
among its members;

2. Sustain its revenues (even during periods of drought) to meet loan payments;
and

3. Develop a well monitoring and control program that insures compliance with
mandates that is administratively feasible for LA WMA and acceptable to the
Colorado State Engineer.

In general, LA WMA desires an operating structure that is fair, has maximum flexibility
for both LA WMA and its members to deal with risk and contingencies, promotes
efficient use of water, reduces unnecessary depletions and is administratively feasible.

Pumping vs. Depletion vs. Replacement ~'

Pumping of groundwater by LA WMA members impairs Arkansas River flow, but the
relationship between plllTIping and the impact on the river is complex. It is important to
note however that replacement water for impaired river-j/ow is the major cost factor for
LAWMA. To achieve water efficiency and fairness, pumping by individual members
should be directly related to this cost factor. It may not be feasible to rate every well by
the amount of replacement water it requires for otfset. As an alternative, we have related
assigned depletion factors of wells to the amount of replacement water as follows:

I. Pumping vs. depletion: The amount of depletion is related to pumping by factors that
vary among users. LA WMA has four types of agricultural irrigators: tributary,
supplemental, sole- flood, and sole-sprinkler. Commercial and municipal water users
are excluded from this analysis because they already have their own offsetting water
rights. Depletion factors are the fraction of groundwater depletion associated with the
level of pumping. Total depletion is estimated at 29,997 afin a normal year and
39,992 af in a dry year.

2. Pre-compact plllTIping allowances and other modifications reduces the impact on the
river from groundwater depletion. Based on these adjustments, we use a factor that
reduces the amOlll1t of depletion to the level necessary to protect senior rights and
compact obligations. From analysis by Helton & Williamsen, P.C. the amount of
replacement water for a normal year is 18,049 af The replacement factor is calculated
as (18,049/29,997= 0.602) in a normal year and as (24,435/38,992 = .627) in 1st and
2nd dry years.

3. The adjustment for plllTIping to depletion to replacement is indicated in Table I. 1bis
is a table of pumping demands (desired levels) by the different type of irrigators.
Associated with desired pumping are the amount of depletion and the amount of
required replacement water. Note that in a dry year, pumping demand increases
substantially among supplemental users. These users would increase pumping to

EnWater Resource Consultants September 5,1997 Final Report

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