Sava River basin

The sub-basin of the Sava River covers considerable parts of Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro and a small part of Albania. A large part of the population of each of the first four riparian countries live in the basin, ranging from approximately 25% to approximately 75% of the total number of inhabitants (Bosnia and Herzegovina: 75.0%, Slovenia: 61.4%, Croatia: 49.75%, Serbia: 24.9%).

Hydrology and hydrogeology

The Sava River emerges in the mountains of western Slovenia, and flows into the Danube in Belgrade, Serbia. The river is the third longest tributary (about 945 km) to the Danube, and the largest by discharge (1,722 cu m/s, at its mouth). In Croatia, the average discharge of the Sava River immediately upstream from the mouth of the Sutla River is around 290 cu m/s; it is 314 cu m/s in Zagreb, and around 1,179 cu m/s at the point where the Sava exits Croatia.

The morphology of the terrain of the basin varies. While rugged mountains (the Alps and the Dinarides) dominate in the upper
part, the middle and lower parts of the sub-basin are characterized by flat plains and low mountains. The areas in the south, in Croatia, Bosnia and Herzegovina, Montenegro and Albania, drained by tributaries ending in the middle section of the Sava watercourse, are characterised by mountainous landscape. Elevation varies between 2,864 m a.s.l. (Triglav, Slovenian Alps) and about 71 m a.s.l. at the mouth of the Sava.

The Sava receives water from a number of rivers, many of which are also transboundary. The most important is the Drina (itself transboundary); its main tributaries are the Piva, Tara, Lim and Uvac rivers.

The Sava sub-basin hosts large lowland forest complexes and the largest complex of alluvial wetlands in the Danube basin (Posavina - Central Sava basin).

The Sava is a fine example of a river where some of the floodplains are still intact, supporting both mitigation of floods and biodiversity. There are six designated Ramsar Sites; a number of areas of ecological importance are under national protection status.

The Sava sub-basin is characterized by diverse geological structures and a complex tectonic setting under which two main units stand out, determining the type of aquifers that occur: the Pannonian area with dominant inter-granular aquifers and the Dinarides with mostly limestone aquifers.

The following transboundary aquifers were identified as hydraulically linked to the surface waters of the Sava River basin, and included in the First Assessment:

(1) Cerknica/Kupa (No. 96), shared by Croatia and Slovenia;

(2) Radovica-Metlika/Zumberak (No. 98), shared by Slovenia and Croatia;

(3) Bregana-Obrezje/Sava-Samobor (No. 99), shared by Slovenia and Croatia;

(4) Bizeljsko/Sutla (No. 101), shared by Slovenia and Croatia;

(5) Srem-West Srem/Sava (No. 107), shared by Serbia and Croatia;

(6) Posavina I/Sava (No. 108), shared by Bosnia and Herzegovina and Croatia;

(7) Kupa (No. 109), shared by Bosnia and Herzegovina and Croatia;

(8) Pleševica/Una (No. 110), shared by Bosnia and Herzegovina and Croatia;

(9) Lim (No. 111), shared by Serbia and Montenegro;

(10) Tara massif (No. 112), shared by Serbia and Bosnia and
Herzegovina; and,

(11) Macva-Semberija (No. 113), shared by Serbia and Bosnia and Herzegovina.

Since the First Assessment, further research by some of the countries has revealed the existence of additional transboundary groundwater bodies that form part of the earlier identified aquifers. Information on the transboundary aquifers that have been identified as hydraulically linked with the surface water systems of the Sava River are already in the First Assessment. It is likely that the list developed is not exhaustive.


Hydropower generation, agriculture and industry are the main economic sectors, sharing the major part of the available water resources in the sub-basin. The construction of water regulation structures and weirs at its tributaries; drainage networks, and flood protection systems, in combination with water abstractions, have caused hydrological and morphological alterations, including disconnection of adjacent wetland/floodplains. Interruption of river and habitat continuity and loss of wetland areas in the lower-middle and lower Sava areas are among the impacts. Erosion is an issue of local character reported by Croatia.

Organic, nutrient and hazardous substances pollution are also important pressure factors. Untreated municipal and industrial wastewater and agricultural run-off are the main pollution sources. Unsustainable disposal of wastes (including these from mining activities) is also of concern. Sediment management, both in terms of quality and quantity, is an additional issue. Invasive species is a potential threat to biological diversity.

Status and transboundary impacts

The risk assessment carried out by the ISRBC for the Sava and its tributaries for impacts, except from hazardous substances pollution, from organic, nutrient and other pollution as well as by hydromorphological alterations, has shown that the risk is rather high for the Sava — 83% of the water body is at risk, while 10% is possibly at risk. With regard to its tributaries, 33% are at risk.


Addressing the identified issues will need time and the investment of considerable resources at national level. A step to address the issue of hazardous substance pollution will be taken by establishing a cadastre of industrial emissions of dangerous and harmful substances. Action at national level and adoption of appropriate management approaches and instruments is necessary for addressing the aforementioned issues. The necessary cooperation to deal in an integrated way with the range of managerial challenges in the sub-basin is conducted through the International Sava River Basin Commission (ISRBC) established under the Framework Agreement on the Sava River Basin (FASRB).

The FASRB was signed by Bosnia and Herzegovina, the Federal Republic of Yugoslavia, the Republic of Croatia and the Republic of Slovenia in 2002, and entered into force in 2004. The FASRB integrated all aspects of water resources management, and became the framework of cooperation among the Parties to the agreement. The four Parties to the FASRB financially support, on an equal basis, the operation and the work under the ISRBC and its Secretariat. Costs of activities that fall under the interest of a certain country(ies) may be financed by them. Additional resources for specific activities under the work-programme have been raised by the ISRBC Secretariat from the European Commission and the international donor community.

Having the Secretariat as its administrative and executive body, the ISRBC has worked for the achievement of the goals of the Agreement. In this regard, a set of activities for the rehabilitation of the Sava River waterway and the development of navigation, a priority issue, have been implemented, and relevant work is on-going. While navigation is important for the economic development in the basin, the interventions in the watercourse for rehabilitation of navigation and the construction of related hydro-engineering structures may become additional pressure factors. ISRBC is cooperating with joint management bodies of international watercourses elsewhere in Europe, with the aim of using available experience and developing appropriate action for the minimization of impacts.

The process for the preparation of a River Basin Management Plan (RBMP - in accordance with the WFD) is on-going and is expected to be finalized by the end of 2011. The Sava River Basin Analysis Report was developed as a first step towards this direction. The Analysis deals with all main surface and undergroundwater bodies; it looks at the hydrological and morphological characteristics, assesses the quantitative and qualitative status of waters, and also deals with monitoring and economic issues. A programme of measures is under finalization, and the RBMP has been drafted. The Analysis provides the basic information background also for the preparation of the Sava River Basin Flood Risk Management Plan (in accordance with the EU Floods Directive).

A number of integrated information systems, the Geographical Information System, the River Information Services (for the improvement of navigation safety), and the Flood Forecasting and Early Warning System are planned to be prepared by 2012 (according to the Strategy of implementation of the FASRB). The Accident Emergency Warning System is in place; enhancement of countries’ capacity is needed before the latter becomes fully operational.

With regard to monitoring, there are 90 quality- and 148 quantity- monitoring stations in total operated by the Parties to the FASRB. Bilateral agreements regarding exchange of information/data exist between some countries. Agreement of all countries on the provision of the most relevant data is the eventual goal. There are also twelve TransNational Monitoring Network stations (in the framework of ICPDR) operating in the Sava River Basin. Individual countries are responsible for different stations. In addition to monitoring, the riparian countries are planning and implementing water resources management measures at national level, in line with the national legal framework and strategic planning documents, and with varied success.

A project linked to climate change adaptation (being executed by the World Bank) will, among others, provide input for planning appropriate adaptation measures to be incorporated in the programme of measures; the aim is to address issues linked to the impacts of climate change in the basin.

Cooperation among the Parties to the FARSB through the ISRBC represents the most advanced effort of its kind in the South-Eastern Europe, showing the way to the riparian countries of other shared basins. The participation of Montenegro in this will be an additional step towards the integrated management of the sub-basin. Montenegro has already been approached in this regard by the ISRBC.