Review of 'Assessing SDG indicator 6.4.2 “level of water stress” at major basins level'

This paper describes a method to disaggregate the indicator 6.4.2 (level of water stress) by major river basin. The analysis was performed using the GlobWat soil water balance model and global geospatial data consistent with national statistics published in AQUASTAT, the FAO’s global information system on water and agriculture. When a river basin spans across more than one country, the water stress calculated by country can be very different from that calculated by river basin since the counting of the renewable freshwater resources from one country to another is highly dependent on the official agreement and treaties that regulate the flow of those resources between countries. This problem is hydrologically solved once the accounting of the water resources is done on the major river basin as a whole. The disaggregation by river basin allows the identification of hotspots where actions should be prioritized and reveals that the area affected by a high or critical water stress spans across all continents with the exception of Oceania. It offers also the possibility of an analysis of freshwater withdrawals by sector, which may become crucial for the definition of water management policies in the context of the economic development of a country.