Analysis of Colorado-Big Thompson Project Operation With Respect to East Slope Diversions and Non-Charge Deliveries

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1 it The storage targets for these runs in thousands of acre -feet are shown in the following tabulation: The storage targets used in Run A were the average end -of -month contents during 1983 -98. The storage targets in Runs B and C were lower in the winter and spring so that Big Thompson River water that became available in April, May, June, and July could be stored. It can be seen that the storage targets in Runs B and C call for filling the two reservoirs at the end of July. The beginning storage values in all runs were the actual reservoir contents at the end of October 1982. These simulations assume that at least 200 cfs of water has to be brought through the Adams Tunnel during November through March to avoid potential snow and ice problems on the west slope. The values in column 11 of Table 6 for 1983 -88, 1990, and 1993 -98 were taken as the historical east slope diversions for Run A even though they may be larger than what actually occurred. Table 12 shows the historical monthly and annual average Adams Tunnel diversions and the monthly and annual Adams Tunnel Diversions from the three simulations for water years 1983 -98. In Run A, the Adams Tunnel diversions averaged 224,500 acre -feet annually which compares well to the historical average of 225,900 acre -feet annually, especially considering that the historical Adams Tunnel diversions included some Windy Gap water. Other differences between the historical and Run A values in individual years are due to the variation between the actual reservoir contents and the storage targets and the way these variations affected Adams Tunnel diversions. Our incomplete data indicated that the Windy Gap water carried through the Adams Tunnel averaged about 6,000 acre -feet annually during 1987 -98. In Run B, when the diversions of Big Thompson Project water were increased with deliveries of both charge and non - charge water, the Adams Tunnel diversions were reduced to an average of approximately 14 - Runs B and C --- Month I Carter Horsetooth Carter Horsetooth t November 71.2 96.4 i i......_.._........................_..._........._......................_............................__...................._ 49.0 .0 ._ ..... . .. ....... ............ .; _........._.... December _.........._ ..........................................._........._...._...!....._.............................._.._......................._........................ 82.4 106.3 i 57.0 79.0 _ . . . .................. ................ . . . . .....6......9. ..... ..... . .......... . ...._ ..... ...........................:..- January _..._...............1111. _.....__......._.......i 91.9 ...:.............._............._..............---..... ....._...._........................... _.._.....__......_...._......_. , 117.7 I ........_......_......__..,.... 64.0 90.0 .................. .... .........................._.............__..........................._........................._.......__......................_........__....__.._...... February 100.0 ........................_.........................._._..__................_..._..........._.............._.._..._....._.._.............._._.... ............................... _111.1. } 127.9 72.0 .................._............ 100.0 ..._.._........................ -. _._.... . .... ............__..._..........._. March R. _........ _. --........................._.__.............._._.......__..._......__..................._..._............,._.............._._...._..........._._._......_......._......._...............,........_......._........_..................... ...1...1 j 105.6 135.7 79.0 111.0 _......._........_._....__ ..............._................._.........;............_......_._..........._...._........._........._... April j 105.6 .__...:......................_. : 136.3 83• _.._......... ........._......_......_......_ ._ ..................... ._............. ... _.. .._.11...11...._ ............. -i . May......__......_ .. .............._..._..........._ ........ .......101.2_._......._..._...' _.._........._._.._............_......._.......... ..............................' ................._ 131.7 _. 87.0 ............. ..._......._.._........._...... _ ...... 123.0 June _... _........._......_.........__._ I 96.9 ........._. _._. ..._._._.__..._........__..._._ _.....�............_ -. ........._..._._.......__..._ 133.4 100.0 140.0 _.._........._.._.._........_ .... _.._._.......................1 ....................._.............._......._._........._........._...... Jul Y .__......_.__......._.... - .. .._............................ 79.6 _ ....................................._._._._................._.............. 113.5 i i ........ _...................._..._;_ ....... 112.2 ..........__........... _......_ ..... ..... ._......._... ........... 156.7 i _..............._............... .._.._..._....._.._ ........ .... __..._ ........................_............__..........._._.......... August .� ._..........__................. ....._._.._.._._._... 4............................ _ ........... .................._..._. _..__...._;...._.............__ �...._........................_ 100.2 89.0 � _....._......_...._....__...... ............... 124.0 1 _._................._......... ...........__.. ............... , September _.._ ...............:__.__. .................64 59.5 ._......................................_._._........_ i 65.0 91.0 ; E _..._........_........_.........._..........._............ October 1......_........._ ........................._ .... _. ..... _...._. j 61.5 _93.0 .._................ .._......._. _.._.............................................,............._......................................_...................._........................_................_._...._...... 91.9 42.0 ...................._........., 58.0 The storage targets used in Run A were the average end -of -month contents during 1983 -98. The storage targets in Runs B and C were lower in the winter and spring so that Big Thompson River water that became available in April, May, June, and July could be stored. It can be seen that the storage targets in Runs B and C call for filling the two reservoirs at the end of July. The beginning storage values in all runs were the actual reservoir contents at the end of October 1982. These simulations assume that at least 200 cfs of water has to be brought through the Adams Tunnel during November through March to avoid potential snow and ice problems on the west slope. The values in column 11 of Table 6 for 1983 -88, 1990, and 1993 -98 were taken as the historical east slope diversions for Run A even though they may be larger than what actually occurred. Table 12 shows the historical monthly and annual average Adams Tunnel diversions and the monthly and annual Adams Tunnel Diversions from the three simulations for water years 1983 -98. In Run A, the Adams Tunnel diversions averaged 224,500 acre -feet annually which compares well to the historical average of 225,900 acre -feet annually, especially considering that the historical Adams Tunnel diversions included some Windy Gap water. Other differences between the historical and Run A values in individual years are due to the variation between the actual reservoir contents and the storage targets and the way these variations affected Adams Tunnel diversions. Our incomplete data indicated that the Windy Gap water carried through the Adams Tunnel averaged about 6,000 acre -feet annually during 1987 -98. In Run B, when the diversions of Big Thompson Project water were increased with deliveries of both charge and non - charge water, the Adams Tunnel diversions were reduced to an average of approximately 14