1. SWC Methodology - TWG February 11, 2015 Settlement Document Subject to I.R.E. 408

2. Agenda http://idwr.idaho.gov/News/WaterCalls/Surface%20Coalition%20Call/default.htm#CM-DC-2010-001 ItemTime 11:30 - 2:00 Introduction and Overview of assignments. (Cresto)  Natural flow predictor models  Cropping Patterns  RISD predictor tools  Irrigated Acres  Supplemental groundwater acres 22:00 - 2:45Natural flow predictor models (Cresto)/ (Brockway) 32:45 – 3:00Break 43:00 – 3:45Cropping patterns (Anders) 53:45 – 4:30RISD predictor tools (Anders) 64:30 – 4:45Irrigated acres (Anders) 74:45 – 5:00Schedule next meeting and identify topics for discussion (Cresto)

3. Natural Flow Predictor Models

4. Current April Natural Flow Models SWC Member Equation (less one standard error) R2R2 A&By = 0.0092x - 19.7470.887 AFRD2y = 0.0742x - 141.140.8317 BIDy = 0.0344x - 2.58530.7964 Milnery = 0.0102x - 19.4120.9243 MIDy = 0.0484x + 2.71780.7896 NSCCy = 0.1562x - 53.0050.8952 TFCCy = 0.0658x + 626.370.5416 Where: y = Natural flow April – October for the SWC Member (AF); x = Heise Natural Flow (April 1 – July 31). USBR/ACOE Heise forecast is used in April. *To error on the side of the SWC, natural flow predictions are one standard error below regression line.

5. Variable NameDescriptionUnits HeiseAprtoJulKAFUSBR Hydromet Heise Natural Flow April - JulyKAF MarWell1USGS Well: WL-9S 25E 03CAC1 March depth to waterFeet MarWell2USGS Well: WL-2N 37E 02ABA1 March depth to waterFeet MarWell3USGS Well: WL-3N 37E 12BDB1 March depth to waterFeet MarWell4USGS Well: WL-8S 24E 31DAC1 March depth to waterFeet MarWell5USGS Well: WL-8S 24E 31DAC1 March depth to waterFeet RupNovtoMarRupert Agrimet Total Precipitation November - MarchInches TYHEE USGS 13075910 PORTNEUF RIVER NR TYHEE ID Total Flow November - MarchAF LastYearNF7to9TFCC Natural flow diversions July - September, lagged by 1 yearAF SpringCreek11to3 USGS 13075983 SPRING CREEK AT SHEEPSKIN RD NR FORT HALL ID Total Flow November - MarchAF SpringCr3USGS 13075983 SPRING CREEK AT SHEEPSKIN RD NR FORT HALL ID Total Flow MarchAF Devils11to3 USGS 13089500 DEVILS WASHBOWL SPRING NR KIMBERLY 10S 18E 04AAD1S Total Flow November - MarchAF Devils3 USGS 13089500 DEVILS WASHBOWL SPRING NR KIMBERLY 10S 18E 04AAD1S total Flow MarchAF Box11to3USGS 13095500 BOX CANYON SPRINGS NR WENDELL ID Total Flow November - MarchAF Box3USGS 13095500 BOX CANYON SPRINGS NR WENDELL ID Total Flow MarchAF Briggs11to3USGS 13095175 BRIGGS SPRING AT HEAD NEAR BUHL ID Total Flow November - MarchAF Briggs3USGS 13095175 BRIGGS SPRING AT HEAD NEAR BUHL ID Total Flow MarchAF TwoOceans71NRCS Two Oceans Plateau (837) Snow Water Equivalent on July 1Inches HEIAprtoJuneUSBR Hydromet Heise Natural Flow April - JuneKAF SpringJantoMay USGS 13075983 SPRING CREEK AT SHEEPSKIN RD NR FORT HALL ID Total Flow January - MayKAF NANRCS Spring Creek Divide (779) Snow Water Equivalent on July 1Inches NANRCS Togwotee Pass (822) Snow Water Equivalent on July 1Inches NANRCS Phillips Bench (689) Snow Water Equivalent on July 1Inches 2OcTowSum of Two Oceans Plateau and Togwotee Pass Snow Water Equivalent on July 1Inches Variables Tested in MLR Models. Variables in Bold were the ones chosen for use in models. SummaryVariablesTested.xlsx

6. New TFCC April Natural Flow Predictor TFCC= 62.01 (Heise) +12,980(Box) – 609,600 Where: TFCC = TFCC natural flow supply from April to October; Hei = Heise natural flow forecast from April – July in (KAF); Box = Box Canyon total flow from November through March (KAF). Adjusted R 2 pSEDOFF-statistic 0.8664<0.00138,0102175.6

8. Changes to Mid-Season Prediction Mid-season adjustment to include upward adjustment of mitigation obligation if the update shows increased shortfall. The current methodology requires a mid-season update. However, the past mid-season updates occurred too late in the season.

9. Review of Current Methodology Updates occurred in late August and only in those years when there was a predicted shortfall in April. Forecasted Supply = Preliminary Storage Allocation + YTD Natural Flow Diversions + Forecast Natural Flow Diversions for remainder of the season Forecast Natural Flow Diversions for remainder of the season o A&B, AFRD2, MID, Milner, and MID typically have little to no natural flow diversions in late August, September, and October. o NSCC and TFCC forecasted natural flow diversions were based reach gains from analogous years

11. New Mid-Season Predictors July 1 make predications with the idea of issuing an order around July 15. This is typically after the day of allocation, especially in dry years. Switch from analogous years to regressions models.

12. July 1 MLR Predictor Models SWC Member Predictor Model Natural Flow Diversions (July – October) Adjusted R 2 SEF-Statistic BIDBID = 19.86(Heise) + 1018(SpringCreek) + 1719(TwoOceans) - 113,3000.867212,81051.06 MIDMID = 28.35(Heise) + 1577(SpringCreek) + 2434(TwoOceans) – 172,260 0.880817,49057.63 NSCCNSCC= 93.26 (Heise) + 2708.5(SpringCreek) + 4609 (TwoOceans) – 346,520 0.900339,82070.22 TFCCTFCC = 37.61 (Heise) + 2629(SpringCreek) + 3616(TwoOceans) + 137,100 0.830431,24038.54 Where: Heise is the total Heise natural flow from April – June in (KAF); SpringCreek is Spring Creek total flow from January - May (KAF); TwoOceans is the July 1 Snow Water Equivalent (in) on July 1.

17. July 1 Linear Predictor Models SWC Member Predictor Model Natural Flow Diversions (July – October) R2R2 SE A&BA&B = 269.28(TwoOceans) - 84.1350.9497509 AFRD2AFRD2 = 1972.9(TwoOceans) - 59.480.91265,015 MilnerMilner =685.63(TwoOceans) +12.7970.89981,880 Where: TwoOceans is the July 1 Snow Water Equivalent (in) on July 1. * 1997 was not included in regresssion analysis.