WEAP
Water Evaluation and Planning System
Vinay Nangia, Ph.D.
International Center for Agricultural Research in the Dry Areas
Regional Knowledge Exchange on Decision-support
Tools and Models to Project Improved Strategies for
Integrated Management of Land, Water and
Livelihoods
How much river water can a user use?
International Center for Agricultural Research in the Dry Areas
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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How much river water can a user use?
International Center for Agricultural Research in the Dry Areas
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 (30 in 2012)
Key model development steps
1. Draw the system schematic
2. Identify data for system components
3. Enter data and run the model
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WEAP Highlights
International Center for Agricultural Research in the Dry Areas
Integrated water resources planning system
GIS-based, graphical drag & drop interface
Basic methodology: physical simulation of
water demands and supplies
Additional simulation modeling: usercreated variables and modeling equations
Scenario management capabilities
Links to spreadsheets & other models
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Defining the study area
and time steps for analysis
Creating of the current
account
Creating of future
scenarios
Evaluation of results
International Center for Agricultural Research in the Dry Areas
Modeling process in WEAP
WEAP system elements
International Center for Agricultural Research in the Dry Areas
Demand sites: A set of users sharing physical
distribution system (geographical)
Catchments: Points created to account for
precipitation, ET, runoff, irrigation and yield from
agricultural and non-agricultural fields
Reservoirs: Reservoir sites on the river
Stream flow gauges: Points where actual flow
measurements are acquired, can be compared with
simulated values
Groundwater nodes: Represents groundwater
sources and aquifers
Waste water treatment plants
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Can do
High level planning
and strategic analysis
at local, national and
regional scales
Demand management
Water allocation
Cannot do
Daily operations
Least-cost
optimization of supply
and demand
International Center for Agricultural Research in the Dry Areas
WEAP Capabilities
Examples of analyses
International Center for Agricultural Research in the Dry Areas
Sectoral demand analyses
Water conservation
Water rights and allocation priorities
Groundwater and streamflow simulations
Reservoir operations
Hydropower generation
Pollution tracking
Ecosystem requirements
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WEAP for vulnerability…
International Center for Agricultural Research in the Dry Areas
Alternative baseline scenarios can examine
vulnerability of water supplies to different
demographic, technological, and
climatalogical/hydrological futures
and adaptability…
Alternative policy scenarios can explore demand and
supply management options for adapting to future
vulnerability
Implications for the multiple and competing demands
on water systems
Implications of policies can be evaluated (ability to
meet water needs, hydropower availability, pollution
loadings, costs, etc.)
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Irrigation
Livestock
Ecosystems
Total
Water Demand
Domestic
Mining
Commercial
Major Cities
Industrial
International Center for Agricultural Research in the Dry Areas
Sectoral water demands
SECTOR
SUB-SECTOR
END-USE
DEVICE
Agriculture
Cotton
Rice
Wheat
...
Irrigation
...
Furrow
Sprinkler
Drip
Industry
Electric Power
Petroleum
Paper
...
Cooling
Processing
Others
Standard
Efficient
...
Municipal
South City
West City
...
Single Family
Multi-family
...
Kitchen
Bathing
Washer
Toilet
...
International Center for Agricultural Research in the Dry Areas
Illustrative Demand Structure
Rainfall-runoff catchment method
Mass balance “2 bucket” method
Root zone soil moisture and below
Physically-based (soil, plant, climate, irrigation)
Computes crop ET, surface runoff, subsurface
lateral seepage, deep percolation to GW, applied
irrigation water
Suitable for climate change scenarios
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International Center for Agricultural Research in the Dry Areas
Demand methods in WEAP
Demand methods in WEAP
International Center for Agricultural Research in the Dry Areas
Per capita “unit” water use method
Unit rate: Unit water use rate (e.g.: L/person, L/ha,
L/home)
Total activity level: Total level of activity for the
demand category (people, area, homes)
Demand volume = Unit rate X Total activity level
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Ag demand (Physical parameters)
International Center for Agricultural Research in the Dry Areas
Soil
Soil moisture holding capacity
Hydraulic conductivity
Initial soil moisture
Plant
Crop coefficient (Kc)
LAI (crop canopy to control surface runoff)
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Ag demand (Physical parameters)
International Center for Agricultural Research in the Dry Areas
Climate
Precipitation
Temperature
RH
Wind speed
Latitude
Melting point temp (snowmelt runoff)
Freezing point temp (snowpack accumulation)
Irrigation
Lower soil moisture threshold (to start irrigation)
Upper soil moisture threshold (to stop irrigation)
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Urban demand
International Center for Agricultural Research in the Dry Areas
Urban indoor (per capita)
Single family
Multi family
Commercial
Industrial
Urban outdoor (catchment)
Single family
Multi family
Commercial
Large landscape
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Supplies
International Center for Agricultural Research in the Dry Areas
Rivers
Groundwater
storage capacity
maximum monthly withdrawal
natural recharge
Diversions (e.g. canals, pipelines)
Reservoirs
Other (e.g. desalination)
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Click and
drag to
create a
new
demand site
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Schematic View
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Network
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Data is displayed
numerically and
graphically
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Data View
International Center for Agricultural Research in the Dry Areas
Results View
Results can be
displayed in wide
range of formats
and scales
Availability
International Center for Agricultural Research in the Dry Areas
Evaluation version available at no charge (CDs
available here) or download from
http://www.weap21.org
Full version requires license, available from SEI
Training is needed for majority of users
System requirements
Windows 95 or later
32 MB of RAM (64 MB suggested)
Imports from/exports to Excel and Word (not
required)
Uses standard ArcView GIS shape files. ArcView is
not required.
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Thank you
International Center for Agricultural Research in the Dry Areas