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Transboundary Water Assessment Programme (TWAP)

Story by IW:LEARN July 25th, 2017

The TWAP is the first global and quantitative indicator -based assessment of transboundary water systems (aquifers, lakes, rivers, large marine ecosystems and open ocean). It addresses two goals: 1) enabling an evidence-based priority setting process for GEF and other international organizations; and 2) formalising partnerships with key institutions so that transboundary considerations are integrated into regular assessment programmes.

Southern Asia Transboundary Waters (ESA 2003)
Southeastern Asia Transboundary Waters (Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC)

TWAP is poised to help identify core indicators to support national monitoring and reporting of targets required to realize the Sustainable Development Goals for the period 2015 - 2030. TWAP freshwater indicators map to SDG 6 on Clean Water and Sanitation, notably Target 6.6 (protection and restoration of mountains, forests, wetlands, rivers, aquifers and lakes). TWAP marine indicators support SDG 14 on Oceans, Seas and Marine Resources, and all its targets.

Below is the global map of risks by theme (rows), and by water category (column). The thematic averages are in the last column, and the water category averages are shown on the last row of each regional set of risk tiles. Southern Asia and Southeastern Asia are the regions most at risk.

Reference: McManus et al. (2016). Crosscutting Analysis, UNEP, 2016.


1. Five water-category specific comparative assessments covering;

2. Quantitative indicator- based methodology for classifying water systems into five risk categories, from very high to very low risk

3. A crosscutting analysis of the five water systems with a high-level summary of patterns and trends.

4. A Compendium of Water System Information Sheets arranged into 14 TWAP regions and presented as 12 annexes of the crosscutting analysis

5. A Summary for Policy Makers per water category in 6 UN languages.

6. A central data portal with all supporting data and publications ( and linking water-category specific websites and databases

Over the long term, it is envisioned that these baseline assessments will be updated periodically and that the changing states of transboundary waters are better tracked to ensure that the essential ecosystem services they provide are maintained in perpetuity.

For more information on the Transboundary Waters Assessment Programme, go to to download all the publications and explore the quantitative indicators used in the global assessment. Water system profiles are available at major partner agency links provided in the website.