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season. The New Ish Ditch Company enlarged the capacity of Ish Reservoir by almost 5,000 ac- <br />ftunder the terms of a 1905 agreement with the Boulder Larimer Ditch Company (aka Old Ish <br />Ditch Company). Under this agreement, the Boulder Larimer Ditch Company has the right to the <br />first 2,546 ac-ft of storage water, with the remaining storage water split 20 percent to the Boulder <br />Larimer Ditch Company and 80 percent to the New Ish Ditch Company. Based on its current <br />active capacity of 7,061 ac-ft, the Ish Reservoir storage capacity entitlements for the two ditch <br />companies are as follows: <br />• Boulder Larimer Ditch Company -- 3,449 ac-ft (2,546 + 0.2 * 4,515 ac-ft) <br />• New Ish Ditch Company -- 3,612 ac-ft (0.8 * 4,515 ac-ft) <br />The Boulder Larimer Ditch system is operated as a demand system whereby water is ordered by <br />and delivered to shareholders when the shareholder requests deliveries. There are 1,000 shares in <br />the Boulder Larimer Ditch Company and the 600 shares in the New Ish Ditch Company. <br />Shareholders can order storage deliveries and C-BT water based on share ownership and number <br />of units, respectively. As a general practice, releases from Ish Reservoir followed by C-BT water <br />are used to supplement direct flow water through the Boulder Larimer Ditch. The general <br />operating strategy in a typical year is as follows: <br />Storage diversions do not begin until early- to mid-April since winter flows are not often <br />sufficient for diversion unless the river comes up after rain and/or snow events. Storage <br />diversions occur through May or as long as the spring runoff continues. The first 2,564 ac-ft <br />of storage in Ish Reservoir goes into the Boulder Larimer Ditch Company account. Any <br />water stored above this level is split 20 percent to Boulder Larimer Ditch Company and 80 <br />percent to the New Ish Ditch Company. <br />Direct diversion for irrigation generally starts near the end of May and continues for two to <br />four weeks for as long as the river stays high enough to permit direct diversions. The 1905 <br />agreement between the two ditch companies establishes that after 2,564 ac-ft is stored, the <br />first 40 cfs of direct flow goes to the Boulder Larimer Ditch company with the remaining <br />water available at the headgate conveyed for storage (where it goes into both ditch company <br />accounts, as described above). After the spring runoff, the river flows are not generally high <br />enough to permit this level of diversion. <br />As the river drops, the available water in storage is delivered to shareholders in the two ditch <br />companies through the separate outlet ditches. <br />The ditch companies generally call for C-BT water after the available storage is exhausted. <br />The transbasin water is used through the end of the irrigation season, generally through late- <br />S eptemb er/early-October. <br />Where to find more information <br />^ The Water District 5 Meeting Notes prepared for SPDSS Task 3 -Identify Key Diversion <br />Structures contain additional information on the Boulder Larimer Ditch and Ish Reservoir <br />within the Water District. <br />^ The SPDSS Draft Irrigated Parcel Mapping has information regarding the irrigated acreage <br />under the Boulder Larimer Ditch system and associated service area. <br />Boulder Larimer Ditch Memorandum.doc 10 of 11 October 28, 2004 <br />