PROJC01741 ‎(3)‎

• Contract/PO #: C153768
• Contractor Name: Lower Arkansas Water Management Association
• Contract Type: Loan
• Water District: 67
• County: Bent
• County: Prowers
• Bill Number: SB 96-124
• Loan Projects - Doc Type: Feasibility Study

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Stream Depletions. The stream depletion is the difference between the diversion and the
return flow for a specific time period. The return flow component from tail water, runoff from the
irrigated fields, occurs fairly quickly. However, the return flows caused by deep percolation and
seepage losses take much longer. The timing and quantity of ground water return flows were
estimated using the Glover method (1987, Schroeder). This method requires transmissivity and
specific yield of the aquifer and the distance to the Purgatoire River. The irrigated land is
located over valley fill alluvium and terrace deposits, and ranges from about 500 feet to over 3
miles from the river. The weighted value for transmissivity was estimated to be 50,000 gpd/ft2 ,
the specific yield was estimated to be 0.2, and the average weighted distance to the river was
measured at 6,500 feet. The resulting monthly factors indicate fairly steady and uniform return
of ground water.

The stream depletions averaged 4,917 acre-feet annually for 1950 through 1993 and
6,372 acre-feet annually for 1980 through 1993 as shown in Table 7. A monthly summary of
the water budget components is shown in Table 8. It shows that the stream depletions as a
percentage of the pro rata diversions range from 28.2 percent in November to 82.8 percent in
August. In December, January and February, the stream accretions total 257 acre-feet, or 3.5
percent of the cumulative diversions for March through November.

Use as a Replacement Source. In the future, LAWMA will divert all water that is available to
the Highland Canal in priority. A portion, 6.08 percent, would be delivered to the non-sellers
and the remainder would be measured and returned to the Purgatoire River through a
wasteway. Alternatively, only the non-sellers share would be diverted and LAWMA's share
would remain in the river and be measured by a new stream gage. The replacement credit
would be equal to LAWMA's prorata diversion volume multiplied by the following stream
depletion rates:

March ................. 45.2%
April ................. 64.6%
May ................. 69.7%
June ................. 77.3%
July ................. 80.9%
August ................. 82.8%
September ................. 70.7%
October ................. 38.9%
November ................. 28.2%

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