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<br />
<br />Mr. William E. Green
<br />. March 1 1, 1997
<br />Page 2
<br />
<br />In 1986, I analyzed the acreage irrigated with water from the Highland Canal. The
<br />results of this analysis indicate that approximately 3,000 acres can be associated with these
<br />3,569 Highland shares. The modified Blaney-Criddle method was used to estimate the
<br />. consumptive irrigation requirements for these lands with climatic data for the Las Animas
<br />weather station and a representative cropping pattern. As shown in Table 3, the resulting
<br />historical consumptive use averaged 4,641 acre-feet annually during 1950-93, or about 1.30
<br />acre-feet per share. These estimates of historical consumptive use were based on
<br />conveyance, lateral, and maximum farm efficiencies of 90, 95, and 75 percents, respectively,
<br />which were obtained from the Colorado Water Budget prepared for Kansas v. Colorado.
<br />These estimates do not include a full consumptive use allowance for the irrigation that
<br />occurred during November through March, which would increase the overall consumptive use
<br />slightly and will be appropriate to include in the final analysis. I believe that LA WMA will
<br />receive credit for the historical consumptive use in its replacement plan.
<br />
<br />The Fort Bent Ditch Company is a mutual ditch company that owns the Fort Bent
<br />Canal and its associated water rights. There are a total of 11,651.2 shares outstanding in
<br />the Company. The water for the canal is diverted from the south bank. of the Ark.ansas River
<br />in sec. 1, T. 23 S., R. 49 W., about 5 miles downstream from John Martin Dam. The
<br />company owns water rights totaling 228.51 cfs, which are summarized in Table 1.
<br />
<br />The water diverted into the Fort Bent Canal averaged 15,498 acre-feet (1.33 acre-feet
<br />per share) during water years 1950-85. The Colorado Water Budget indicates that Fort Bent
<br />Ditch water is 55.67 percent consumptive, resulting from a canal efficiency of 77 percent, a
<br />lateral efficiency of 94 percent, and a farm efficiency averaging 75 percent. In addition, 5
<br />percent of the canal and lateral losses were consumed through evaporation and transpiration.
<br />These factors all combine to indicate that the historical consumptive use of Fort Bent water
<br />averaged 0.74 acre-foot per share during 1950-85, for a total of 262 acre-feet for the 354
<br />shares LAWMA is acquiring. The historical use and consumptive use of these Fort Bent
<br />shares will be analyzed in more detail as part of the feasibility study. These shares are
<br />especially logical for acquisition by LA WMA since LA WMA already owns 120 Fort Bent
<br />shares and has the use of an additional 1 ,286 Fort Bent shares owned by the City of Lamar.
<br />
<br />Status of ReDla~ement Water Supolv
<br />
<br />I have estimated that pumping by LAWMA members will average about 85,000 acre-
<br />feet annually. Of this total, about 65,000 to 70,000 acre-feet will occur through mainstem
<br />irrigation wells, 3,000 to 4,000 acre-feet will occur through irrigation wells in out-of-the-
<br />mainstem area, but in tributary areas, and 12,000 to 18,000 through municipal and
<br />commercial wells. These values are based on the study of pumping ,estimates made for
<br />LA WMA members since 1990 and pumping estimateS made by or for the State Engineer for
<br />Water District 67 during 1950-94. There will be considerable variation in annual pumping,
<br />however, especially with the mainstem irrigation wells. I expect mainstem irrigation pumping
<br />will vary from about 50,000 to , 00,000 acre-feet annually.
<br />
<br />The replacement requirements for this pumping can be expected to average 18,000
<br />acre-feet annually and to range from about 14,000 to 27,000 acre-feet annually. These
<br />requirements are based on (1) the presumptive depletion factors from the Amended Rules and
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