EXHIBIT 120 Walker River Basin Decision Support Tool (DST) Version - PDF document

EXHIBIT 120

Walker River Basin Decision Support Tool (DST) Version 2.0 Department of Geography, University of Nevada, Reno Douglas P. Boyle

Original DST Mission – ca. 2006-7 What: Develop a Decision Support Tool (DST) that includes the important spatial, temporal, and vertical complexities of the hydrologic behaviors of the of Walker River Basin to inform proposed water right acquisitions aimed at increasing flows to Walker Lake. Why: Options for water right acquisitions (purchases and/or leases) are being obtained. DST will provide an estimate of how much additional water will make it to Walbuska based on different acquisitions and climate conditions. Department of Geography, University of Nevada, Reno Douglas P. Boyle

Our Modeling Approach 1. Understand the process, scale, and data needs/constraints of the Walker River Basin - supply and demand. 2. Identify and evaluate existing and previous modeling and data collection efforts. 3. Identify and obtain available hydrologic information for the system. 4. Develop physically realistic hydrologic models of the supply and demand components of the system. 5. Create and test a DST, based on the physical models, that can be used to inform water acquisition decisions. 6. Use the DST. Department of Geography, University of Nevada, Reno Douglas P. Boyle

Phase I & II 1. Development and initial testing of DST completed December 2008. Phase I completed. 2. The “Water Group” formed in January 2010. Designed, conducted, analyzed and discussed experiments with DST aimed at understanding Walker River basin behavior. 3. Phase II started in August 2010. Based on needs of Water Group, effort to improve DST started in January 2011. 4. DST version 2.0 presented to Water Group in January 2012. Continued interactions with Water Group planned through CY 2013. Department of Geography, University of Nevada, Reno Douglas P. Boyle

Overview of DST 2.0 Model Components MODSIM River Basin Management system PRMS models of headwater areas (Supply Side) MODFLOW models of Mason & Smith (Demand Side) Department of Geography, University of Nevada, Reno Douglas P. Boyle

What is MODSIM? MODSIM River Basin Management Decision Support System Network comprised of nodes and links Includes tools for priority, variable colors of water, and optimization. Provides user with access to all variables and parameters within time loop. Capable of linking with other hydrologic models (e.g., MODFLOW, Agricultural Demand PRMS, etc.). GW New 20% Lands 5% GeoMODSIM implemented in GIS Flood software. 5% Decree Decree Storage 60% 10% Department of Geography, University of Nevada, Reno Douglas P. Boyle

MODSIM Conceptual Model Boundary Conditions: Obs t = 100 5 P1: Med. 35 HRU 1 D1: 35 5 HRU 2 P2: High 30 D2: 30 0 P3: Low 15 5 HRU 3 D3: 25 PB: Very High 30 DB: 30 Boundary Conditions: Obs t = 30 Department of Geography, University of Nevada, Reno Douglas P. Boyle

Application of MODSIM to Walker River Basin MODSIM upstream boundary conditions - driven with observed monthly streamflow for 1996 through 2011. Reservoir storage and evaporation simulated at Bridgeport and Topaz. Diversion node for each ditch in Mason and Smith Valleys; HRUs defined by agricultural area served by each ditch. Agricultural areas with primary pumping defined as separate HRUs. Department of Geography, University of Nevada, Reno Douglas P. Boyle

MODSIM Mode 1: Historic Ditch Demand Dx : Decree, storage, and flood water diverted at each ditch based on historic delivery records P1, D1 according to priority, Px . Water balance computed at each HRU 1 R1 HRU on 100m grid scale based on crop type, NSE net water requirement, supplemental pumping, P2, D2 farm efficiency, ditch loss, etc. P3, D3 R2 Water applied becomes ET, HRU 2 infiltration, or runoff. R3 HRU 3 Iterative MODSIM/MODFLOW convergence MODSIM – partitioning and distribution of all surface water MODFLOW – interaction of surface and groundwater Department of Geography, University of Nevada, Reno Douglas P. Boyle

MODSIM Mode 2: Crop Demand Dx : Decree, storage, and flood water diverted at each ditch based on crop demand and ditch level P1, D1 priority , Px . Historic diversions used to evaluate model. HRU 1 R1 Water balance computed at each HRU on 100m grid scale based on crop type, NSE net water P2, D2 requirement, supplemental pumping, farm efficiency, ditch loss, etc. P3, D3 R2 HRU 2 Water applied becomes ET, infiltration, or runoff. R3 HRU 3 Iterative MODSIM/MODFLOW convergence MODSIM – partitioning and distribution of all surface water MODFLOW – interaction of surface and groundwater Department of Geography, University of Nevada, Reno Douglas P. Boyle

MODSIM Network Legend MODSIM Streams & Drains Department of Geography, University of Nevada, Reno Douglas P. Boyle MODSIM Ditches

West Hyland HRU Legend MODSIM Streams & Drains MODSIM Ditches Department of Geography, University of Nevada, Reno Douglas P. Boyle West Hyland HRU

Water Balance Modeling Units Legend MODSIM Streams & Drains MODSIM Ditches West Hyland HRU Department of Geography, University of Nevada, Reno Douglas P. Boyle Model Grid

Primary GW HRU & GW POU Legend MODSIM Streams & Drains MODSIM Ditches West Hyland HRU Model Grid Primary GW HRU GW POU Department of Geography, University of Nevada, Reno GW Well Douglas P. Boyle

Portion of West Hyland With Supplemental GW Legend MODSIM Streams & Drains MODSIM Ditches West Hyland HRU Model Grid Primary GW HRU GW POU GW Well Department of Geography, University of Nevada, Reno Douglas P. Boyle West Hyland Modeling Units With Supplemental GW

Parameter Walker DST Water Balance 2.0 Uncertainty Wabuska Gage HRU 1. Determine available surface water at POD (Surf 1 ) 2. Surf 2 = Surf 1 *(1-DCL) 3. CD = Ag. Area * NIWR (State Engineer) 4. CIWR = CD / (E Farm ) AF * 5. P Req = CIWR – Surf 2 4 SP Max = # Acres A 6. SP Max = f(Permits) 7. P Act = P Req or Balance of SP Max RO 8. App = P Act + Surf 2 9. OFL = App*(1-E Farm ) App 10.RO = R Factor *(OFL) 11.RCH = (1-R Factor )*OFL P Act DCL Terms and Definitions Surf 1 Surf 1 = Surface Supply at POD P Req = Pumping Required Surf 2 DCL = Ditch Conveyance Loss P Act = Pumping Actual Surf 2 = Surface Supply at Ag. Area App = Application CD = Crop Demand OFL = On Farm Loss E Farm = Farm Efficiency R Factor = Runoff Factor NIWR = Net Irrigation Water Req. RO = Runoff CIWR = Crop Irrigation Water Req. RCH = Recharge SP Max = Seasonal Pumping Maximum Department of Geography, University of Nevada, Reno Hudson Gage Douglas P. Boyle Strosnider Gage

Consumptive Use Comparison (2007) West Hyland Non-NDOW METRIC ET NIWR DST Consumptive Use 0.7 0.6 0.5 0.4 Feet 0.3 0.2 0.1 0 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Oct-07 Department of Geography, University of Nevada, Reno Douglas P. Boyle

Example Wabuska Calibration Streamflow Simulated Observed 120000 100000 80000 Acre-Feet 60000 40000 20000 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Department of Geography, University of Nevada, Reno Douglas P. Boyle

Basin-wide GW Pumping (Mason and Smith) Walker Basinwide GW Pumping Comparison Observed DST (53,15,35) 160 140 120 Thousand Acre-Feet 100 80 60 40 20 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 Department of Geography, University of Nevada, Reno Douglas P. Boyle

Example West Hyland Demands & Deliveries Department of Geography, University of Nevada, Reno Douglas P. Boyle

Application No. 80700 • Summary – 646.16 Acres of West Hyland HRU – 7.745 CFS of Decree Rights – Claim Numbers: 23, 23A, 35, 44, 67, 89 – Priority Dates: 1874, 1877, 1880, 1881, 1887, 1888, 1891, 1894, 1896, MODSIM Streams & Drains 1900, 1901, 1904, 1906 West Hyland HRU Change App. Parcels Department of Geography, University of Nevada, Reno Douglas P. Boyle

Application No. 80700 – DST Methods The DST was modified from the baseline model run to reflect, as closely as • possible, the effects of the proposed change over calendar years 1996 through 2011. The results from the scenario model run are then compared to the results from the baseline model run. The change application parcels are removed from the DST modeling grid • (i.e. fallowed) & supplemental pumping is retired for the parcels. The volume of surface water that is not applied in the scenario run (i..e., • Application 80700 water) is calculated based on the fraction of the areas taken out of production relative to the total non-NDOW HRU area. It is equal to the sum of the decree, flood and storage water delivered to the same areas in the baseline run. The Application 80700 water is “protected” at the West Hyland point of • diversion and allowed to flow to Wabuska. The 80700 Wabuska water is the amount of Application 80700 water that • makes it to Wabuska Department of Geography, University of Nevada, Reno Douglas P. Boyle

Scenario Results (1996-2011) 35,000 29,500 30,000 Storage = 5,627 26,834 25,344 25,000 Flood = 3,111 Total Acre-Feet (1996 - 2011) Decree = 20,762 20,000 15,000 10,000 5,000 221 92 0 Retired GW Pumping App. 80700 Water 80700 Wabuska Water Shortage Surplus Department of Geography, University of Nevada, Reno Douglas P. Boyle