WEAP

WEAP (Water Evaluation and Adaptation Planning) is an integrated water resources planning platform developed by the Stockholm Environment Institute. It represents water systems as flexible node-link networks combining catchments, rivers, reservoirs, groundwater aquifers, demand sites, and infrastructure. Operating on monthly or daily timesteps, WEAP balances water allocation across competing municipal, agricultural, industrial, and environmental requirements using a priority-based linear programming solver while accounting for hydrology, crop evapotranspiration, climate scenarios, and stream water quality.

Practising water engineers and regional planners reach for WEAP to perform integrated water resources management (IWRM) studies, climate change impact assessments, and policy trade-off evaluations. The software features native integration with MODFLOW for groundwater modeling, QUAL2K for stream water quality, and PEST for parameter estimation. However, WEAP is a Windows-only desktop application, requires commercial license fees for private consulting work, and setting up coupled groundwater or water quality models can involve significant setup complexity.