2008-03-28_REVISION - C1981008 (3)

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03f 31 f 2008 13:36 9702475104 DMG DURANGO OFFICE United States Depart~rient ot~ A~rlic~iltare ~NRCS N~u~t Resources car,iservation service Jlm Boyd. Fteaourge Goneservationle~t P. O. ~3ox 29 IVvrvw4bd. CO 81423 1Vlarcl~ 21, 200$ jlm_bayd~co. usde.~ov 970-J2'7'~246-OF~IC~ 9~0~327-4247-FAQ PAGE 03f 07 Division ofReclamatian, Mining and Safety ~~ ~ ,~ ~QQ~ Department of N~tturaI Resources - Cval Programs 701 Carnlino del :f~io, Room 315 Durango, CO 81:34f E`iuran~o Field ~fliea Dlvlai0n of ReclemAifctln~ kgninp send SaPBIy .~f~°' Imo: Post Mine Vegetation can Prime Farmland, New 1:•Ivrizatit Mine, Pe~xllait G81.-008 Dean Concerned Parties: Mr. Gubka, mine engineyer for New hlorizons Mine in Nuclei, Colorado, recently submitted to the data on the amauatt of imigaLYon water that the Colorado Cooperative Ditch Coany (CC~Ditch) has historically de;live:red to the Nucla. Park. In his analysis of the data he states that: "insufficiem wat~T quantity is being transported by the CC-I)iteah to the: Park to malfe SO shares of water equivalent to 1.5 CFS, thew amwuriit to satisfy the requireme;~s ofthx~ee sideroti sprinklers." I wilt herein oountier that this is generally not a relevaatt concern, nor a coxr~pletely accurate stateniiei~t, giaen the; following information. In my previous legtter, dated March 4, 2408, I explained design cr, xteria for three siderol] sprmkl.ers se;rv~g, about 70 acres of irrigated alfalfa, with each sideiroll utilizing O.S cubic feet per second (cfs) acid covering ~3 acres. I i>rs;clueied in that discussion an iunnigation schedule demonstrating that tb~,e peak irrigation demands of alfalfa could be satisfied with thrtre siderolls operating sirriulta~aeously th~inteen (13) out of every fifteen (15) days. This side~+oll sprinkler system is conservatively designed to mieet the extrezrie growing corkditions of high te:mpe:ratures, or the peak consunnptivc water tese of the crop. This period typically occurs in the; rirtoztths of June and July, at !which time the CC-Ditch is generally able to provide the water qu~ttities needed (see aRtached spreadsheet). At other times of the growing season, the alfalfa crop needs signifisrantly less water, which can also be consistently supplied by the CG-]~itoh Company and adequately applied to tlxe crop by the sideroll sprinkler system. Enclosrxl is a water budget for alfalfa growing in, the Nucla arEa. The cansun~ptive water use of the crop at~d the effective precipitation included in the budget are long-term clit>niatC induced averages. Irrigation events ate scheduled when vxi~e half of tt~e available soil moisture xs depleted by the crop, i1a this cage 3. S inches. 't'his depletion occurs at diffexe;uit rates during the growing season, as is evidt,rrt by the ni-onthl~+ consumptive use columm (see water budget). In the month of .May only 3.61 inches of water is used by alfalfa, so only one irrigation evert that replaces this depletion is necessary in May, In the month of July 6.83 inches of water is used by the crop, so two irrigations are; required, each replacing about 3. S inches of depletion. Sincxr it takes thirteen (13) days for each. sieieroll to cover its natended area of 23 aches, all three siderolls will need to be operating simultaneously t26 out of 31 days) to meet this peak demand in July- 7ria M.burai Reoaunx Conservefimi Serrloe works in p~+b+erehlp wNh elw Amaficen People m Caheerre end Sustain nehmal I~bSOUtcee on pAvals Imtda_ An Equgi DpparlunFgr A~ovid~r 6rnd Empleyel.