1. River Basin Simulation with WEAP Water Evaluation and Planning System
David Rosenberg
CEE 6490 – River Basin Planning

2. 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
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3. 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
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4. 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
Draw the system schematic
Identify data for system components
Enter data and run the model
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5. Select Applications Location Features Water Purposes Reference(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
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
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And many more at

6. 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
Activity 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.
Enter work in Google Doc #1
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7. 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.
Complete work in Google Doc #2
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8. Calculate Allocations
Draw the schematic (previous slides)
Determine delivery targets for demand sites (demands)
Assign priorities to demand sites (delivery preferences)
Determine water availability
Sources
Return flows
Allocate remaining available water to meet delivery target of highest priority demand site
Repeat Steps 4 and 5 for next highest priority site.
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9. 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.
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?
Demand Site
Priority [rank]
Delivery Target [ac-ft/yr]
City
2 (lower) 30
Agricultural
1 (high) 60
Google Doc #3
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10. 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.
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?
Demand Site
Priority [rank]
Delivery Target [ac-ft/yr]
City
2 (lower) 30
Agricultural
1 (high) 60
Google Doc #4
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11. 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!
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12. 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
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13. Adding Reservoirs (cont.)
In WEAP
First use in-stream flows to meet Demand Site targets
If in-stream flows inadequate, withdraw from reservoirs
Withdrawal a function of reservoir storage
Can also assign priorities to refill reservoirs
Withdraw to meet full delivery target
Withdraw reduced amount (buffer coefficient)
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14. WEAP Allocation Math
In each time step, WEAP solves a small linear program
Maximize Demand Satisfaction
Meet supply priorities
Obey demand site preferences
Mass balance
Other constraints
Embed the LP in a time-series simulation (psuedo code)
Such that:
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15. Using WEAP Major Modules Introduce modules today
Schematic
Data
Results
Scenario Explorer
Introduce modules today
Apply & practice in lab exercise
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16. 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
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17. Weaping River Example Schematic
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18. 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
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19. Alternatively, right-click any schematic component to also get to the Data module
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20. Schematic for the Lower Bear River
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21. Schematic for the Lower Bear River
QX1-Bear River
QX61-Malad River
Cache Valley
QX6-Cache GW
Cutler
Bear River Canal Company
New Cache
QX15-South Cache Reach Gain/Loss
New Box Elder County
South Cache
South Cache
QX27-Box Elder GW
QX22-Malad Reach Gain/Loss
QX41-Blacksmith Fork
Box Elder County
Hyrum
QX46-Little Bear
Bird Refuge
Reservoir, proposed
Reservoir, existing
Urban Use
Ag. Use
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Wetland

22. Activity 5. What flow data need to be entered for the Lower Bear River?
Look at the Schematic for the Lower Bear River.
What locations require headflow data?
Which reaches require reach flow data?
Where can you obtain this data?
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23. 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
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24. Alternatively, right-click any schematic component to also get to the Data module
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25. Tree view, Buttons, and Tabs to navigate to desired data
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26. 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
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27. Water demands by Demand Site
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28. WEAP Scenario Explorer
Define and manage scenarios from the Data module
Enter input data here too
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29. WEAP Scenario Explorer (cont.)
Use Scenario Explorer icon to open scenario dashboard
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30. 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.
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