Modeling with WEAP Steven Burian and Erfan Goharian

Modeling with WEAP Steven Burian and Erfan Goharian Hydroinformatics Fall 2013

Learning Objectives • Describe priority-based water allocations • Draw a system schematic (that includes water sources, demand sites, and return flows) • Calculate the streamflow from a watershed using rainfall-runoff methods • Calculate allocations given available water and delivery priorities • Use the WEAP system to set up a schematic, enter data, obtain results, and define + analyze scenarios

Why a IWRM model? • • Allocation of limited water resources concerns regarding environmental quality planning under climate variability and uncertainty need to develop and implement sustainable water use strategies

Water Allocation Modeling • All resources are not available for each user • Also reach gains/losses, reservoir storage, consumptive use, return flows, groundwater, soil moisture, etc. must be considered • 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) • Change in time and locations (spatial and temporal changes) • All the factors should be modeled in order to track water • Key model development steps 1. Draw the system schematic 2. Identify model approach and data for system components 3. Enter data and run the model

System Definition • Include major components • Subsystems • Identify based on project objectives and requirements • Identify connections between components • Relationships or real connections • System boundaries • Create drawing • Labeling components • Arrowed lines • As straight forward as possible

Why WEAP? • software tool for integrated water resources planning • user-friendly framework for planning and policy analysis • Water balance database: WEAP provides a system for maintaining water demand supply information • Scenario generation tool: WEAP simulates water demand, supply, runoff, streamflows, storage, pollution generation, treatment and discharge and instream water quality • Policy analysis tool: WEAP evaluates a full range of water development and management options, and takes account of multiple and competing uses of water systems.

Questions WEAP can answer • What if population growth and economic development patterns change? • What if reservoir operating rules are altered? • What if groundwater is more fully exploited? • What if water conservation is introduced? • What if ecosystem requirements are tightened? • What if a conjunctive use program is established to store excess surface water in underground aquifers? • What if a water recycling program is implemented? • What if a more efficient irrigation technique is implemented? • What if the mix of agricultural crops changes? • What if climate change alters demand supplies? • How does pollution upstream affect downstream water quality? • How will land use changes affect runoff? • etc

Using WEAP • • • Design the schematic Select Methods Data Results Scenario Explorer Notes • Today: introduce user interface • Tuesday: automate use through Application Programming Interface • Next Thursday: Finalize homework and analyses

Schematic • Objects: Rivers, demand nodes, reservoirs, diversion and etc. • Created and positioned within the system by dragging and dropping items from a menu • Arc. View or other standard GIS vector or raster files can be added as background layers • You can quickly access data and results for any node by clicking on the object of interest

Hydrologic Module of WEAP (1) the Rainfall Runoff method (2) Irrigation (FAO Crop Requirements Approach) (3) Soil Moisture Method (4) the MABIA Method

Calculate Allocation • Mass Balance Equation P + Gin – (ET + Q + Gout) = ∆S • More demand sites, water sources like reservoirs and return flows make more complex data requirements and allocation calculations • Integrated Water Resource Management • Hydroinformatics and computer modeling can really help!

WEAP Allocation Method • In each time step, WEAP solves a small linear program Maximize Demand Satisfaction 1. 2. 3. 4. Meet supply priorities Obey demand site preferences Mass balance Other constraints • Embed the LP in a time-series simulation (psuedo code)

Data • Enter data for each schematic component • Rivers: Headflows for each month of the simulation • Reaches: Reach gains for each month of the simulation • Diversions: Minimum flow requirements as reach losses • 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, volumeelevation curve, evaporation, pool definitions, buffer coefficients, priority • Enter data or read from input file

Identify data for system components 1. Determine water availability § § Sources Return flows 2. Identify delivery for demand sites (demands) 3. Allocate water based on priorities to demand sites (delivery preferences) 4. Allocate remaining available water to meet delivery target of highest priority demand site 5. Repeat Steps 4 and 5 for next highest priority site

Example

Precipitation Input

Results • Click the Results icon and recalculate (all scenarios) • Choose results from schematic or dropdown lists • Numerous options to view, tabulate, and export

Next Session • Define and manage scenarios from the Data module and enter input data • Use Scenario Explorer icon to open scenario dashboard • Automate inputting data • Use Scripting in WEAP