Welcome to WEAP's Website WEAP
WEAP is an initiative of the Stockholm Environment Institute.

About WEAP

What's New?
Sample Screens
History and Credits

Using WEAP
User Guide
Videos (YouTube)

User Forum
Members List
Edit Profile

Additional Support
University Courses

About Us
SEI-US Water Resources Program
Please Contact Us

Interested in Energy?
Read about LEAP: SEI's software for energy planning.

Link WEAP and LEAP for combined Water-Energy planning.
Watch a video demo!

WEAP Features

An intuitive GIS-based graphical interface provides a simple, yet powerful, means for constructing, viewing, and modifying the configuration. The user designs a schematic of the system using the mouse to "drag and drop" elements to be added to the system. These elements can be overlain on a map built from ArcGIS and other standard GIS and graphic files. Data for any component can be edited directly by clicking on the desired symbol in the schematic. The user may consult the context-sensitive help feature from anywhere in WEAP. Wizards, prompts, and error messages provide advice throughout the program. With WEAP's highly flexible and comprehensive reporting system, the user may customize reports as graphical, tabular or map-based output and select from a number of formatting options (e.g., metric or English units, years, absolute levels, percent shares, or growth rates). Specific report configurations can be saved as "favorites," which can be combined into "overviews," or summaries, of key system indicators; these overviews can then be retrieved quickly for review.

WEAP is available in the following languages (some not fully translated): English, Arabic, Chinese, Farsi, French, Greek, Korean, Portuguese, Russian, Spanish and Thai. An option on the WEAP menu allows the user to switch between these languages. Please contact us if you want to join other volunteers to help translate WEAP into these and other langauges.


  • Integrated water resources planning system
  • Built-in models for: Rainfall runoff and infiltration, evapotranspiration, crop requirements and yields, surface water/groundwater interaction, and instream water quality
  • GIS-based, graphical "drag and drop" interface
  • Model-building capability with a number of built-in functions
  • User-defined variables and equations
  • Dynamic links to spreadsheets and other models
  • Embedded linear program solves allocation equations
  • Flexible and expandable data structures
  • Powerful reporting system including graphs, tables and maps
  • Context-sensitive help and User Guide
  • Minimal requirements: runs under Windows XP, Vista, 7, 8 or 10 with 256 MB RAM


WEAP consists of five main views

Schematic - GIS tools allow you to easily and quickly configure your system, including "drag and drop" capability to create and position system elements. Add ArcGIS and other standard GIS vector or raster files as background layers. Quickly access data and results for any element in the system.

Data - model-building tools help you create variables and relationships, enter assumptions and projections using mathematical expressions, and dynamically link to Excel for data importing and exporting

Results - detailed and flexible display of all model outputs can be viewed in graphs, tables and on the map. The graph and map formats allow for animated viewing of results through time.

Scenario Explorer - design a group of summary graphs to highlight key system indicators for quick review. Explore how changes in data can affect results.

Notes - document your data and assumptions.

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