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Water Evaluation and Planning system (WEAP)


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WEAP is a water resource management model. It operates on the principle of water balance accounting and is applicable to municipal, agricultural and natural biological systems. WEAP incorporates hydrologic and water resources simulations with scenario analysis. The results of the integrated simulation and scenario analyses can be used to evaluate applications such as: water demand management capabilities, reservoir management options, hydropower generation and energy demand, water rights allocations, environmental impacts (water quality outcomes, biological habitat availability outcomes), etc.

Geographic Location

The model was developed in the Aral Sea region in 1989 with sponsorship from the Stockhom Environment Institute (SEI). SEI continued to support the deveopment of WEAP through SEI-Boston. Over the last two decades, WEAP has been applied in countries and river basins around the world.


The WEAP model requires water supply and demand data as input data. The source of the water supply data can either be from an external hydrology model (i.e VIC or DHSVM) or can be built internally within the WEAP model. Demand data can include municipal, commercial, industrial and agricultural demand. Demand can also be represented by instream water demands (aquatic habitat for biological organisms).


WEAP outputs can include simulations of the following: stream or river flows, water allocations between conflicting water users (i.e. in-stream uses versus out-of-stream uses), reservoir functions and hydropower production and water rights allocations.

Linkage to Other Models

WEAP can be linked to a variety of hydrologic models and biological population models.

Level of Effort

Varies with complexity of questions and hypotheses. Requires fundamental understanding of hydrologic processes, detailed data of estimated demand for respective water sectors. Calibration of reservoir operation can be an extensive process. Depending on hypotheses, can require expert knowledge of biological organism of interest.

Basin Scale Opportunity Assesment