The Why and How of Colorado Aug. Plan Decrees Maintaining Historic Return Flows

Transcription

1 The Why and How of Colorado Aug. Plan Decrees Maintaining Historic Return Flows Colorado Aquifer Management Conference American Ground Water Trust Nov , 2012 Jon Altenhofen, PE South Platte Projects Manager (Projects: ARA, PRRIP, ADI)

2 THE WHY and HOW: The WHY is the GOAL of maintaining historic return flows- Returnflows to the river (river gains from groundwater inflows) supply downstream senior surface rights and the junior tributary irrigation wells deplete these returnflows. The HOW is a Colorado Water Court approved Augmentation Plan. Numerous Terms and Conditions with much emphasis on: (a) Tributary Aquifer Response Functions for lagging activities at wells/recharge ponds to future depletions/accretions at the river in terms of amount, timing and location. (b) Water Balance Accounting (for actual and projections) at the river listing ALL depletions versus replacement supplies so negative effects are fully augmented/replaced so no shortages to demands of senior downstream rights.

3 Historical South Platte River Flows Pre-Irrigation John Charles Fremont, Explorer, July 1842 six miles from our resting place near Julesburg we crossed the bed of a considerable stream, now entirely dry ---a bed of sand. Post-Irrigation Ralph Parshall, Colorado A&M College Report, 1922 The practice of irrigating maintains a constant return flow beyond all expectations Perhaps no other Colorado stream has such an abundant return flow as the South Platte River. Post- Well Irrigation Ralph Parshall, Talk to Ft. Collins Rotary Club, Aug. 29, 1956 titled The Water Problem the area north and south of the river between Kersey and Julesburg, more than 4000 irrigation wells are being pumped we cannot continue this practice of depleting the underground reservoir at the present rate.the depletion of the return flow to the river is going to have a marked effect upon senior rights along the South Platte.

4 South Platte Basin

5 Point Flow analysis for Monday Nov 26, 2012 at 1500 hrs A point flow analysis shows the important fact of SP hydrology-it s a return flow hydrology and administration/aug. plan decrees protect that fact.

6 Looking west upstream S. Platte at Tamarack from Red Lion Bridge June 15, 1994; 25 cfs 25 cfs at StLi Compact Call Hmy1 34 cfs Pic Peter 41 cfs I&PV 60 cfs & call Divs. drying the river South Platte Tributary Alluvial gains/returnflows to the lower river of about 2 cfs/mile on June 15, 1994

7 Some Groundwater Numbers for the South Platte in Colorado --The South Platte tributary aquifer is an unconfined Valley Fill surficial aquifer ; an alluvial aquifer made up of sands and gravels. USGS estimated volume of groundwater storage at about 8 MAF. --USGS estimated 1 MAF annually of recharge to the aquifer from canal/reservoir seepage and onfarm deep percolation. --The South Platte River forms a natural drain for the alluvial aquifer. Groundwater seepage to S. Platte River averages about 515,000 af/yr (USGS).

8 Alluvial Wells Cons. mass/energy Effects of an Alluvial Well Alluvial Irrigation Well

9 Decreed Augmentation Plans

10 USGS in cooperation with the Colorado Water Conservation Board (CWCB) Six S. Platte Reaches (Brighton, Greeley, Weldona, Brush, Sterling, Julesburg) Six Maps each Reach (well locations, bedrock and water table contours, saturated thickness, transmissivity, and Stream Depletion Factor; SDF in days)

11 Timing of Lagged Groundwater Response at River AWAS Computation Options (Alluvial Water Accounting System) and go to IDS AWAS --- SDF (Effective Stream Depletion Factors via Jenkins) Glover Methods (i.e., alluvial aquifer-no flow boundary condition) URFs via Numerical Groundwater Model (ie; MODFLOW) Timing example using SDF Method (Days)

12 USGS SDF contour lines (one-pt calibration at 28% effect)

13 Alluvial Aquifer Grid for T, X, W

14 Appendix C Tamarack Ranch State Wildlife Area Recharge Project Unit Replacement Factors for All Recharge Ponds Month Pond 1 Pond 2 Pond 3 Pond Total URFs (Unit Response Functions) developed for Tamarack from MODFLOW numerical model

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16 Table 1-1 Lower Logan Well Users (LLWU) Inc. 03CW208 UPDATED ACCOUNTING THROUGH AUGUST 2012 MONTHLY ACCOUNTING FORM / TABLE Depletions and Augmentation Supplies Water Year: 2012 Nov11 Dec Jan12 Feb Mar April May June July Aug Sept Oct Totals Days in month for Wtr Yr DEPLETIONS (a) Irrigation Well Depletions for senior wells (senior to , #44618); 1974-Current Pumping (b) Irrigation Well Depletions for 2 most junior wells with No Court Decree; 1974-Current Pumping (c) Augmentation Well Depletions above the Harmony #1 -- Due to Aug Well use thru Previous WY (App Date , #56414) (d) Historic Return Flows -- Due to Prewitt Res. releases thru Previous WY (App Date , #56002) (e) Recharge Well Depletions -- Total through current pumping (App Date , #56002) The net effect below Harmony #1 is added in below W = Total Depletions Above Harmony # AUGMENTATION REPLACEMENT SUPPLIES Recharge Accretions Occurring above the Harmony #1 Bravo Ditch areas and Bravo recharge sites Iliff & Platte Valley Ditch areas and IPV recharge sites Harmony #2 Ditch areas and UHD recharge sites Powell Ditch areas and PWC recharge sites SLC recharge sites SSLC recharge sites StLC recharge sites LC recharge sites KF recharge sites Ramsey recharge sites Golden Eagle's use of Rech Acc The net effect below Harmony #1 is added in below Total Accretions Above Harmony #1 (A) Other Aug Credits Harris 00CW181 Decree Computations Net Credit from Other Sources Above Harmony #1 (B) Prewitt Reservoir releases and augmentation well pumping done on days of river call. Call Analysis and resulting Net Shortage/Excess on Call days Monthly Call Records: NO CALLS in Nov-Dec 2011 & Jan-Feb 2012Senior call; days May, 30 days June, 31 days July, 31 days Aug 6 days of senior and 4 days of junior calls in April 2012 Days of Senior River Call above the Harmony # W1 = Net Shortage/Excess on Senior call days above Harmony #1 (W+A+B)*%call days Days of Junior Call above the Harmony # W1 = Net Shortage/Excess on Junior call days [(Sum rows b thru e above)+a+b]*%call days Which of rows b thru e above are summed depends upon which junior call Projections in Red Julesburg Res Junior Call Mar 27-31, 2012 and Res full Mar 31 Prewitt Reservoir Releases in WY2012 Gross Credit=Release minus river shrink Depletions from Release (Replace Historic Returns) on days of call (App Date , #56002) Net Credit from Release (C) Projections in Red Augmentation Well Pumping in WY2012 Total Pumping for credit (at average aug well and 95% conveyance to river for projection) Depletions from this Pumping on days of call (App Date , #56414) Net Credit Aug Wells (D) Exchange Operations Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Y = Total Diversions (See Table 1-2C) NET EFFECT ABOVE HARMONY #1 (X = W1+C+D-Y) ON CALL DAYS (Senior and Junior) Senior call; days May, 30 days June, 31 days July, 31 days Aug Affects Occurring Below the Harmony No. 1 Headgate Senior Call Admin #= No Senior Calls Nov11-Apr Days of Senior River Call below the Harmony # Irrigation Well Depletions for senior wells Occurring below the Harmony #1 (senior to , #44618); 1974-Current Pumping Augmentation Well Depletions below the Harmony #1 -- Due to Aug Well use thru Previous WY (App Date , #56414) Augmentation Well Depletions below the Harmony #1 -- Due to Aug Well use in Current WY (App Date , #56414) UHD and Svoboda Recharge Site Z = Net Effect Below Harmony No. 1 on call days cfs for Augmentation below Hmy #1= NET EFFECT (X+Z) ON CALL DAYS (Senior and Junior) Row AA; Net Effect for Entire Month if Positive If there is no call or compact condition below the Harmony #1 then amount Z does not have to be replaced and is not included in this Final NET EFFECT Row. Recharge well depletions in a month when recharge wells are pumped in-priority after call comes off based on recharge well pumping thru prior month. Accounting Forms prepared by Jon Altenhofen, NCWCD; Joe Frank, LSPWCD; and TZA Water Engineers, Inc.

17 Augmentation Challenge Replacement of ALL out of priority junior well depletions to a downstream senior (calling) right in time, location, and amount Passive Augmentation Supply Less Control on augmentation credit at the river Managed Groundwater Recharge Active Augmentation Supply More Control over augmentation credit at the river BUT cause an additional depletion / return flow replacement Augmentation Wells Reservoir Release to River Ditch Bypass at River Headgate

18 Managed Groundwater Recharge Effects of Groundwater Recharge (both managed and unmanaged) Managed Groundwater Recharge Site

19 Volume (Ac-Ft) South Platte Recharge Total District 1, 2, & 64 Recharge District 1 Recharge District 2 Recharge District 64 Recharge 0 Year

20 This TR-21 is 2 nd Edition from 1994; 1 st Edition was TR-13 from

21 Recharge and Augmentation Well System near Sedgwick, CO

22 SUMMARY: A sustainable S. Platte alluvial aquifer has developed through irrigation and this aquifer has enhanced Colorado irrigation and water use through return flows and groundwater pumping. The challenge is to continue to utilize the aquifer through droughts, growing demands, and increased legal augmentation requirements while maintaining historic return flows. Maximizing the aquifer storage potential through such activities as managed groundwater recharge and augmentation wells (i.e., with proper analysis/accounting for net river effects) can meet current and future challenges to maintain/maximize beneficial use without injury.

23 Recharge at Sunset on the Overland Trail Ranch The End Questions/Comments Recharge pond with snow geese at Condon Ranch

24 Prepare for drought continuing in 2013 Wells will be essential but their effects on river returnflows must be augmented else downstream seniors see a compounded drought effect