The main goal of the Hydrological Study is to enhance knowledge of the water cycle dynamics and components and their spatial and temporal distribution in the Sava River basin by improving hydrological and meteorological data reliability and management in the Sava River basin, considering current climate variability and future climate change.

Using records for a period of about 100 years, the Hydrological Study will create a basin-wide interactive data portal and strengthen capacity for better inform decision-making on sustainable water resources management in the Sava River basin, including analysis of climate characteristics and climate change, high flow regime and floods, low flow regime and droughts, groundwater fluctuation and quality, water balance, inland waterway parameters. 

On July 9, 2025 the kick-off on development of the Hydrological Study took place in Zagreb, Croatia, with about 60 participants in total from across the Sava basin and more.
Participants reviewed implementation arrangements, examined elements of a common methodology for preparation of the Hydrological Study including all analysis that would be performed and analytics tool that will be used, and also discussed the concept design of the web-based interactive data portal.
After many years of data collection and exchange among countries, through activites of the International Sava River Basin Commission (ISRBC) and using the Sava Hydrologic Information System (Sava HIS), that contributed to the general trust in the transboundary water cooperation in the Sava River basin, needs and requirements from the countries for development of a comprehensive hydrological study covering the entire basin were also recognized. Those were drivers to the ISRBC to prepare the project for development of the Hydrological Study covering the entire basin, the first after 1976.
The project is financed by the Global Environment Facility and the World Bank and coordinated by the ISRBC. The work in the next two years will be carried out by a joint venture of regional partners led by Vodoprivredno-projektni biro d.d. (VPB d.d.).
This project marks the first truly all-inclusive, multi-country hydrological study of the Sava basin in nearly half a century, unifying modern data, methods and digital tools in a single, shared framework.

Planned outputs will support better informed basin-wide risk management and help reduce potential losses to people, property, the environment, cultural heritage and the regional economy under increasing hydroclimatic variability, while also contributing to sustainable water resources management through improved protection and more balanced use.

The Hydrological Study and portal are expected to be completed by spring 2027.

See video on the project kick-off and reactions of the meeting participants, below.

Knowledge enhancement of the water cycle dynamics in the Sava basin
through development of a comprehensive Hydrological Study - Kick off