River Basin Simulation with WEAP Water Evaluation and Planning System David Rosenberg NRM + IWRM

Learning Objectives Describe reasons to model priority-based water allocations Draw a system schematic (that includes water sources, demand sites, and return flows) Calculate allocations given available water and delivery priorities Add reservoir storage and release priorities Use the WEAP system to set up the schematic, enter data, obtain returns, and define + analyze scenarios 2NRM+IWRM

How much river water can a user use? River flow ≠ Water available to a user Also reach gains/losses, reservoir storage, consumptive use, return flows, groundwater, soil moisture, Delivery targets and water allocation priorities –Appropriation doctrine (first in time, first in right) –By purpose (e.g.: urban demands before environmental) –By location (e.g.: upstream, then downstream, or reverse) Prior withdrawals and deliveries Changes from month to month and year to year NRM+IWRMDavid Rosenberg 3

How much river water can a user use? (cont.) It’s complicated to track We’d like a model to do this WEAP History –First developed in 1992 –WEAP21 version in 2005 –Already 119 published applications (33 in 2010) Key model development steps 1.Draw the system schematic 2.Identify data for system components 3.Enter data and run the model NRM+IWRMDavid Rosenberg 4

Select Applications LocationFeaturesWater PurposesReference(s) Aral Sea 17 reservoirs 28 demand sites Water supply Lake recession; fishing Water quality Raskin et al., 1992 Upper Chattahoochee, Georgia 1 reservoir 24 demand sites 44 transmission links 10 return flows Water supply Drought management Flood protection Johnson, 1994 Steelpoort basin, South Africa 33 demand sites Ag., urban, mining, and stock water supply Ecological reserve Conservation planning Levite et al., 2003 Sacramento River, CA Ag. & urban wat. sup. Env. Flows & hydropower Climate change adaptation Purkey et al., 2008 And many more at NRM+IWRMDavid Rosenberg 5

Draw a System Schematic Identify the major system components –Water sources (surface and groundwater) –Demand sites (agricultural, urban, etc..) –Source connections to demand sites –Outflows from demand sites after use Example 1: A river can supply water to a city and an agricultural district. The outfalls from agricultural drain pipes and the city’s wastewater treatment plant are located downstream of both diversion intakes. NRM+IWRMDavid Rosenberg 6

Draw a System Schematic (cont.) Example 2: A river can supply water to a city and an agricultural district. The city is located upstream of the agricultural district. 40% of the city’s withdrawals are collected, treated, returned to the river, and available for downstream use by the agricultural district. NRM+IWRMDavid Rosenberg 7

Calculate Allocations 1.Draw the schematic (previous slides) 2.Determine delivery targets for demand sites (demands) 3.Assign priorities to demand sites (delivery preferences) 4.Determine water availability  Sources  Return flows 5.Allocate remaining available water to meet delivery target of highest priority demand site 6.Repeat Steps 4 and 5 for next highest priority site. NRM+IWRMDavid Rosenberg 8

Calculate Allocations (cont.) Example 3: A river can supply water to a city and an agricultural district. The outfalls from agricultural drain pipes and the city’s wastewater treatment plant are located downstream of both diversion intakes. NRM+IWRMDavid Rosenberg 9 Demand Site Priority [rank] Delivery Target [ac-ft/yr] City 2 (lower)30 Agricultural 1 (high)60 70 ac-ft is available in the river this year. The table shows demand site priorities and delivery targets. What water volume is allocated to each demand site?

Calculate Allocations (cont.) Example 4: A river can supply water to a city and an agricultural district. The city is located upstream of the agricultural district. 40% of the city’s withdrawals are collected, treated, returned to the river, and available for downstream use by the agricultural district. NRM+IWRMDavid Rosenberg 10 Demand Site Priority [rank] Delivery Target [ac-ft/yr] City 2 (lower)30 Agricultural 1 (high)60 70 ac-ft is available in the river this year. The table shows demand site priorities and delivery targets. What water volume is allocated to each demand site?

Calculate Allocations (cont.) Always use mass balance to determine water available to a user (or at model node) Allocation calculations get more complicated as add demand sites and return flows Computer modeling can really help! NRM+IWRMDavid Rosenberg 11

Adding Reservoirs Reservoirs are just another supply source Reservoir source availability determined by –Storage at end of previous time step –Reservoir release rules –Reservoir inflows, evaporation losses, etc. Partition reservoir storage NRM+IWRMDavid Rosenberg 12

Adding Reservoirs (cont.) In WEAP 1.First use in-stream flows to meet Demand Site targets 2.If in-stream flows inadequate, withdraw from reservoirs 3.Withdrawal a function of reservoir storage 4.Can also assign priorities to refill reservoirs NRM+IWRMDavid Rosenberg 13 Withdraw to meet full delivery target Withdraw reduced amount (buffer coefficient)

WEAP Allocation Math In each time step, WEAP solves a small linear program Maximize Demand Satisfaction 1.Meet supply priorities 2.Obey demand site preferences 3.Mass balance 4.Other constraints Embed the LP in a time-series simulation (psuedo code) NRM+IWRMDavid Rosenberg 14 Such that:

Using WEAP Major Modules –Schematic –Data –Results –Scenario Explorer Introduce modules today Apply & practice in lab exercise NRM+IWRMDavid Rosenberg 15

WEAP Schematic Drag and drop system node components –Demand sites –Reservoirs, etc. Drag, click, and drop system link components –Rivers –Transmission links –Return flows Add GIS layers to help place components Must include all infrastructure you plan to test in Scenario Explorer NRM+IWRMDavid Rosenberg 16

Weaping River Example Schematic NRM+IWRMDavid Rosenberg 17

WEAP Data Module Enter data for each schematic component –Rivers: Headflows for each month of the simulation –Demand sites: activity levels, use rates, losses, consumption, demand priority (1=highest; 99=lowest) –Transmission links: Max flows, supply preference –Return flows: routing (percent returned) –Reservoirs: storage capacity, initial storage, volume- elevation curve, evaporation, pool definitions, buffer coefficients, priority Enter data for a base case or a scenario Enter data or read from input file NRM+IWRMDavid Rosenberg 18

Alternatively, right-click any schematic component to also get to the Data module NRM+I WRM 19

NRM+IWRM Schematic for the Lower Bear River David Rosenberg 20

David Rosenberg 21 NRM+IWRM New Cache Cache Valley Bear River Canal Company Reservoir, proposed Reservoir, existing Wetland Ag. Use Urban Use Box Elder County Bird Refuge Schematic for the Lower Bear River Cutler QX15- South Cache Reach Gain/Loss QX5-Lower Bear QX6-Cache GW QX22- Malad Reach Gain/Loss QX27-Box Elder GW QX61-Malad River South Cache Hyrum QX46-Little Bear QX41- Blacksmith Fork New Box Elder County

Example 5. What flow data need to be entered for the Lower Bear River? Look at the Schematic for the Lower Bear River. a.What locations require headflow data? b.Which reaches require reach flow data? c.Where can you obtain this data? NRM+IWRMDavid Rosenberg 22

WEAP Data Module Enter data for each schematic component –Rivers: Headflows for each month of the simulation –Reaches: Reach gains and losses each month of the simulation –Demand sites: activity levels, use rates, losses, consumption, demand priority (1=highest; 99=lowest) –Transmission links: Max flows, supply preference –Return flows: routing (percent returned) –Reservoirs: storage capacity, initial storage, volume- elevation curve, evaporation, pool definitions, buffer coefficients, priority Enter data or read from input file NRM+IWRMDavid Rosenberg 23

Alternatively, right-click any schematic component to also get to the Data module NRM+I WRM 24

NRM+I WRM 25 Tree view, Buttons, and Tabs to navigate to desired data

WEAP Results Module Click the Results icon and recalculate (all scenarios) Choose results from schematic or dropdown lists Numerous options to view, tabulate, and export NRM+IWRMDavid Rosenberg 26

Water demands by Demand Site NRM+IWRMDavid Rosenberg 27

WEAP Scenario Explorer Define and manage scenarios from the Data module Enter input data here too NRM+IWRMDavid Rosenberg 28

WEAP Scenario Explorer (cont.) Use Scenario Explorer icon to open scenario dashboard NRM+IWRMDavid Rosenberg 29

Conclusions WEAP can simulate priority-based water allocations Drag and drop interface to draw system schematic Enter variety of data for river, demand site, reservoir, return flow, and other system components View results in numerous formats Use scenario tool to test and view results for changes in model inputs Apply principles after Spring Break for Lower Bear River basin lab exercise and ILO-4. NRM+IWRMDavid Rosenberg 30