The urgency of placing equal focus on climate adaptation alongside mitigation has never been greater. While mitigation – reducing greenhouse gas emissions – is critical to limit future climate change, the impacts of a warming planet are already here and accelerating. Countries and communities must tackle the rapidly evolving conditions we face today.

One essential tool in the toolbox of adaptation planning is the Water Evaluation and Adaptation Planning (WEAP) platform, SEI’s flagship water management software that has supported governments and researchers at all levels in more than 190 countries for more than 35 years.

The WEAP developers at SEI now unveil a new, streamlined look to the website, weap21.org. The website is more modern and user-friendly, with a new focus on climate adaptation and “WEAP in action” features that highlight the many uses of WEAP around the world. The tool itself is also updated with new functions.

WEAP continues to serve as a critical tool for adapting to climate change. From deadly flash floods to prolonged droughts, rising sea levels, wildfires, and extreme heat waves the world over, climate-related disasters are increasing in frequency, severity, and cost. These events are disproportionately affecting vulnerable communities that have contributed least to the problem but face the greatest risks. Adaptation measures – such as resilient infrastructure, early warning systems, climate-smart agriculture and strengthened water management – are critical to protect lives, livelihoods, and ecosystems from unavoidable impacts. Without urgent investment in adaptation, even the best mitigation efforts will be undermined by escalating climate damages, deepening inequality, and threatening development gains. Integrating adaptation into national and transboundary policies, budgets, and planning is no longer optional – it is a life-saving necessity.

WEAP considers the fundamental question of how to be resilient in the face of climate change. What adaptation strategies – whether policies, investments, nature-inspired or manmade infrastructure – will provide human, water, energy, food, and ecosystem security?

WEAP is a leading tool for climate change vulnerability studies and adaptation planning, used across 190 countries with more than 50 000 users. It is incorporated in global adaptation toolkits – such as the Climate Adaptation Knowledge Exchange (CAKE) –  as a key Adaptation Planning and Decision Support tool, and is included in National Adaptation Plans (NAPs).

WEAP offers several features that support water management plans and NAPs.

There are many examples of WEAP applications focusing on climate change. Here we highlight four diverse examples across the globe.

California

SEI works with policymakers and stakeholders throughout California to model complex water systems and explore adaptation strategies. Using WEAP, SEI helps local, regional and statewide agencies create a shared model of watersheds that brings diverse interests and perspectives to the table.

Rwanda

SEI researchers used WEAP to simulate where the water supply is expected to fall short over time due to climate change and limited infrastructure. WEAP reviewed Rwanda’s water supply and demand to identify potential scarcity and conflict between different users, as well as adaptation strategies to shift to more resilience.

An economic analysis then evaluated the macroeconomic implications of different adaptation strategies using WEAP and macroeconomic  model simulations to identify robust options throughout the country.

Central Asia

Water, energy and food security are intertwined challenges in Central Asia, transcending the borders of the five countries that share the Syr Darya and Amu Darya river basins.

The USAID Regional Water and Vulnerable Environment activity (WAVE) linked Kazakhstan, the Kyrgyz Republic, Tajikistan, Turkmenistan, and Uzbekistan to manage shared water, food, and energy resources using governmental collaboration and combining water and energy modelling with macroeconomic analysis.

The program’s goal was to strengthen regional cooperation and develop a shared vision among stakeholders on identifying robust mitigation and adaptation strategies in the face of ongoing climate change.

El Salvador, Guatemala and Honduras

The Upper Lempa River Basin spans Guatemala, Honduras and El Salvador in Central America. It is threatened by degradation of water resources from municipal, rural and industrial pollution, unsustainable land use changes, and over-extraction of water. These threats have resulted in water quality that does not comply with established standards, the eutrophication of lakes, fish kill events, unmet water demands during the dry season, and conflicts over water use. Climate change exacerbates these threats. 

The United States Agency for International Development (USAID) awarded a cooperative agreement to implement the Upper Lempa Watershed Project in 2022 to Winrock International, in partnership with Tetra Tech ARD, SEI and the Center for Water Security and Cooperation. The objective of the project was to work with institutions, municipalities and civil society to address the quantity, quality and reliability of water derived in the watershed via robust adaptation strategies.