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

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 http://www.weap21.org/ NRM+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+IWRM

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 NRM+IWRM

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 NRM+IWRM And many more at http://www.weap21.org/index.asp?doc=16

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 NRM+IWRM

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 NRM+IWRM

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. NRM+IWRM

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 NRM+IWRM

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 NRM+IWRM

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+IWRM

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+IWRM

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) NRM+IWRM

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: NRM+IWRM

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

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+IWRM

Weaping River Example Schematic NRM+IWRM

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+IWRM

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

Schematic for the Lower Bear River NRM+IWRM

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 NRM+IWRM Wetland

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? NRM+IWRM

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+IWRM

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

Tree view, Buttons, and Tabs to navigate to desired data NRM+IWRM

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+IWRM

Water demands by Demand Site NRM+IWRM

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

WEAP Scenario Explorer (cont.) Use Scenario Explorer icon to open scenario dashboard NRM+IWRM

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+IWRM