Photo: Susie Bresney / SEI.

SEI’s flagship water modelling tool now calculates and displays results more quickly, enabling policy-makers, analysts and researchers to more easily use very large models of water systems.

The updated version of the Water Evaluation And Planning (WEAP) system can now calculate large models up to 10 times faster than in the past. Scenarios that once took 10 to 20 hours to calculate now take 1 to 2 hours.

“Modelers can now build more complex models and test many more scenarios than before, helping them to explore a wider range of options and ultimately to uncover more robust solutions,” said Jack Sieber, WEAP’s developer and deputy director of SEI US.

WEAP is the de facto standard for integrated water resource planning, used in 180 countries for policy-making at the watershed, state, national and regional scale. It is user-friendly, free to developing countries, and supports transparent and robust decision-making.

In recent years, SEI has used WEAP to develop the Sacramento Water Allocation Model, or SacWAM, which simulates one of the most complex water systems in the United States. This model of the Sacramento-San Joaquin Delta is being used by the State of California to help make decisions over how to balance both society and ecosystem needs.

In SacWAM and other WEAP models, users can see not just how watersheds and water systems work – but also how they could work under future policies and climate change impacts. This enables policy-makers and stakeholders to see the trade-offs and benefits of various scenarios, and to work together to come up with robust paths to sustainability.

The latest upgrades to WEAP make it practical to run more scenarios and analyze more results than ever before, meaning users can test out more policy options.

For example, a moderately complex model in WEAP that previously took an hour to calculate now completes in six minutes, and the calculation time for very large models, such as SacWAM, has been reduced from 24 hours to two.The results files for these calculations are also now much smaller, allowing users to more easily transfer files from one computer to another.

WEAP also includes numerous other upgrades, including improved handling of very large climate datasets, enhanced scripting support and bug fixes.