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:\ IE'I OR-\.:\ 1)1 ~I TO: File FRO\I: Jon Altelli1.oien, PE, ~C\VCD DATE: Octooer 29,2001 REF: Accretions from Existing Recharge Projects as a 'Vater Source for Colorado's Tamarack Plan In :!ie \Yare:- Action Plan for the Plat:e River Cooperative Agreement, Colorado had stated u.1.at "Excess ac.:retion c:-edits associated with currem ditch recharge programs that are nor r.eeded for well augmentation \yill also be targeted for T ,unarack Phase I and Phase ill". Recharge/augmentation plans, typically done by ditc3 companies. are undertaken for augmentation of irrigation wells belong to shareholders. These plans also ge!le::-ate credits at :he river which are excess to well augmemation needs. This is particularly true in February and :March wjen \~-en depletions are nor out-of-priority. The rabie on !ne reverse side of this Memo lists credits for existing recharge projects for the November through ~larch period. "Ylost of the listed projects ha\-e been operating for more than 10 years so steady state conditions are being appmached. This table routes these credits to the -:\ebraska Stateline at Julesburg by an average S-c loss ractor due to Civersions and evaporation. These accretion credits wiiI ~OT BE PROTECTED and therefore are subject to diversion. By not protecting these accretions to the Stateline, issues oyer injury to other Colorado water rights are avoided. CSF\VS has accepted these credits in Februa.ry and March for the past 4 years as suitable replacement for interim measures for the EFO's along the Front Range dealing with "CSFS permits. \Vith out a 3-State Program. these excess credits would undoubtedly become a major source of water for Colorado entities dealing with direct Federal nexus for Section 7 ESA issues. One legal issue that has arisen is the question of beneficial use in Colorado for these accretion credits from eXlsting recharge projecB. Do these credits haye to go to a beneficial use in Colorado after they have returned to the ri\-er from the prior recharge? I ~omend that they do not because they have already served a beneficial use and they are not being protected to the Stateline. The accretions from these existing projects are similar to accretions iTom the recharge at the CDO\V Tamarack Ranch S\VA. At the Tamarack Ranch S\VA, water was diyened ror the beneficial use of \'.'ildlife habitat at the recharge ponds. The seepage from these ponds accretes to the riwr becoming credit in the Tamarack Plan for the 3-State Program. For existing plans recharging for \\-ell augmentation, I contend that the accretion water has been divened and already pm to a beneficial use because this excess water was a necessary part of delivering other water that W2.S used ror irrigation well augmentation. One could look on this water that became excess as a form of "c:ariage water". \Vhen you recharge in a ditch or pond, seepage or accretions back to the river in the future COiTIe in a11 :nomhs--you dO:lot haye the control to have it return :n just the months when wel! depletions are om-of-prior::.t,,- Eke '-.yith a surface reservoir. Excess credits are a phvsical reality of doim! recharl!e--if you tTV ., ., .. - ...... .. ., to elimi:laIe excess by diyening less to recharge, you will :ieduce the amount of credits that are available for well augmemario:l when well depletions ~e our-of-priority. An analogy to this is the rerum flows that occur from beneficial use for irril!ation. In order Ie have consumptive use bv crops in a field. vou have to have rerum - ., I ., flo'-.\-s (deep percolation belo\v the root zone and surface runoff from the bottom of the field) in order to get adequate water to all the crop in the field. Return flo\'/s are nor consumed on :he field but the diversion of wa:er that becomes return flows are considered an irrigation beneficial use.