Water Evaluation and Planning System (WEAP)

Created: 8/01/2017 - Updated: 2/27/2020


The Water Evaluation and Planning (WEAP) System is a software tool designed to help users with integrated water resources planning. WEAP uses a GIS-based interactive platform to allow high user customization, and helps users generate, integrate, and analyze watershed-specific information related to water supply, demand, and quality, as well as ecological information. This information can be used as a quick snapshot of water supply and demand trends, but can also be run through a scenario generation tool, a policy analysis tool, and a financial analysis module to analyze how future potential changes could affect water quality, supply, and demand and costs of various water-related projects. For example, WEAP has a built-in capability to model shifts in rainfall runoff and infiltration, evapotranspiration, surface water/groundwater interaction, and instream water quality. Users can examine how climate shifts pair with shifts in policy, water infrastructure (e.g., reservoirs, desalination plants, wastewater treatment plants), and other factors to affect water resources in their study area. WEAP’s integrative and highly customizable process facilitates informed decision making by allowing users to compare a variety of scenarios and examine water relationships from a variety of perspectives and scales. Users can also share WEAP-generated information in a variety of formats (graphical, tabular, and map-based), facilitating effective and clear communication with relevant stakeholders.

Example in use: WEAP was used to model the Apalachicola-Chattahoochee-Flint River Basin, which supplies groundwater and surface water to the states of Alabama, Georgia, and Florida. Facing increasing water use conflicts, these states used WEAP to evaluate water use and allocation scenarios, as well as to better understand current supply and demand trends. WEAP ultimately helped these states, along with federal and local partners, to create equitable and resilient water allocation agreements. WEAP was also recently used by the state of Massachusetts to enhance integration of ecological considerations into water supply and wastewater development projects, helping minimize negative impacts of future water infrastructure projects on natural systems.

Phase of Adaptation: Planning


Land managers, water utility managers, natural resource managers, local authorities, planners, policymakers