Neretva River basin
The Neretva River basin is shared by Bosnia and Herzegovina and Croatia, and through the Trebišnjica River, which is hydraulically connected with the Neretva, also by Montenegro. Some 10,100 sq km of the basin area is in Bosnia and Herzegovina, and 280 sq km in Croatia.
The 220 km-long Neretva River has its source in the Jabuka Mountains in Bosnia and Herzegovina, and flows for 20 km through Croatia before reaching the Adriatic Sea. The Upper Neretva River flows through a mountainous landscape; for the last 30 km, from Mostar (Bosnia and Herzegovina) to its mouth, the river spreads into an alluvial delta covering 200 sq km. The average annual flow of the Neretva is 11.9×109 cu m.
The Lower Neretva valley contains the largest and the most valuable remnants of Mediterranean wetlands on the eastern Adriatic coast, and is one of the few areas of this kind remaining in Europe. The area is a significant resting and wintering place for migratory species. The wetlands are also valuable for the ecological services they provide, as well as for their support to local economic activities. The part of the delta area extending into Bosnia and Herzegovina has protected status and Herzegovina has protected status (Hutovo Blato Nature Park). The Hutovo Blato (74.11 sq km) has been designated as a Ramsar Site (2001), and so is the delta area extending in Croatia (designated in 1993). Five protected areas exist in the Croatian part of the delta, covering a total area of 16.2 sq km; two other sites (total of 7.77 sq km) have also been proposed for designation. The protection of the sensitive areas needs to be improved at national level. Moreover, since the delta is a geographical and ecological entity, the two countries should use similar protection requirements and measures to manage it. Besides the wetlands, the basin also includes Dinaric karst water ecosystems.
Hydrology and hydrogeology
Major transboundary tributaries of the Neretva include the rivers Ljuta, Rakitnica, Bijela, Trešanica, Kraljušnica, Neretvica, Rama, Doljanka, Drežanka, Radobolja, Jasenica, Trebižat (right tributaries) and Šištica, Baščica, Prenjska river, Šanica, Bijela, Buna, Bregava, Krupa (left tributaries).
Croatia reports that water scarcity and droughts are observed during summer.
The karst geology of the area results in high interaction between surface waters and groundwater. The Trebišnjica and Trebižat Rivers are characteristic examples. The Trebišnjica River emerges near Bileća town (Bosnia and Herzegovina). It is a characteristic example of a “sinking river” that drains into the underground and reappears; its total length is 187 km above and under the ground. Its average annual flow is 2.5 × 109 cu m. Part of the river’s water drains directly across the borders with Croatia to the Adriatic Sea. Trebišnjica is hydraulically partially linked to the Neretva River, being part of the same karstic hydrogeological basin. The Trebišnjica sub-basin is shared between Bosnia and Herzegovina – where the major part of the sub-basin extends – Croatia and Montenegro; almost the total of the western bank of the Bileća Reservoir belongs to Montenegro. The 51 km-long Trebižat River is also a “sinking river”; the Vrljika River (Croatia) drains into the underground and re-emerges at the Tihaljina spring (Bosnia and Herzegovina), then flows as the Tihaljina-Mlade-Trebižat River.
Pressures and transboundary impacts
The water resources in the Neretva and Trebišnjica basins are important for the economies of both Bosnia and Herzegovina and Croatia. The rivers are crucial for transport, recreation, fisheries and fishing. They are used also for drinking water, irrigation, gravel and sand extraction.
Both Neretva and Trebišnjica are particularly important in terms of energy production. In Bosnia and Herzegovina’s part of the Neretva and Trebišnjica basins, there are 13 reservoirs. Dams with accompanying reservoirs on the Neretva include those of Jablanica, Grabovica, Salakovac and Mostar. A hydroelectric production system has been constructed on the Trebišnjica River. This includes two dams on the river (Trebinje I or Grančarevo and Ttrebinje II, in the Bosnia and Herzegovina) and two channels: a channel through Popovo polje (Popovo field) towards Čapljina plant (Bosnia and Herzegovina), and a second one across the borders towards Dubrovnik plant (Croatia). Additional infrastructure is planned to be constructed through the “Upper horizons” project, which involves regulation of Gatačko, Nevesinjsko, Dabarsko and Fatničko fields. A hydropower plant exists also in the Rama River.
The operation of the different existing infrastructures should be coordinated, taking into account upstream/downstream uses and needs, as well as evolving climatic conditions, so as to prevent potential negative impacts on ecosystems and economic activities. Plans for future hydropower development in both countries should also take these factors into account. Alteration of the hydrological regime as a consequence of water use for agricultural, municipal, industrial, and hydropower generation purposes is a pressure factor. There are water losses due to degraded water supply and distribution systems, and the efficiency of agricultural water use is limited. Other problems include reclamation of wetlands, uncontrolled urbanization and excessive illegal hunting and fishing in the wetlands. The erosion of riverbeds and land, as well as the decline of groundwater levels in the Trebišnjica/Neretva Left coast aquifer (No. 131), have been observed in Bosnia and Herzegovina, together with a reduced springflow in both Neretva Right coast (No. 130) and Trebišnjica/Neretva Left coast aquifers (No. 131).
Point-source pollution (from untreated municipal and industrial wastewaters and uncontrolled dumpsites, both for municipal and industrial wastes) and diffuse pollution (due to unsustainable agricultural practices) exert pressure both on surface waters and on aquifers. The widespread but moderate drawing of polluted water in the Neretva Right coast (No. 130) and Trebišnjica/Neretva Left coast aquifers (No. 131) exacerbates the situation. Bosnia and Herzegovina reported that water pollution by nutrients, pesticides, heavy metals and organic compounds are issues of concern. Access by the population to sanitation systems has been low in Bosnia and Herzegovina, and there is room for improvement in treatment facilities for municipal wastewater. There is pollution from municipal wastewater in the areas of Metković, Rogotin and Opuzen in Croatia. The following has been reported: occasional microbiological pollution in the Neretva Right coast (No. 130) and the Trebišnjica/Neretva Left coast aquifers (No. 131) in Croatia; moderate nitrogen, pathogen and organic compounds pollution in the Neretva Right coast aquifer (No. 130); and wide but moderate nitrogen, pathogens and heavy metals and some local, moderate pesticide pollution in the Trebišnjica/ Neretva Left coast aquifer (No. 131) in Bosnia and Herzegovina. Groundwater pollution has effects at the transboundary level.
The cumulative impacts of these pressures have led to degradation, in terms of quality and quantity, of surface waters and groundwater, and subsequently of associated ecosystems.
Pressures and impacts have in many cases an upstream – downstream character; for instance, the regulation of the flow of the river has led to salt water intrusion in the Neretva delta, as well as the reduction of sediment deposition in the alluvium affecting the natural system, its functions and services, as well as economic activities downstream. This is not applicable everywhere throughout the area, since the existence of karstic geological formations may, for example, cause impacts of point pollution that occur downstream to be transported in groundwater to other parts of the basin.
Responses
A number of water resource management plans and measures are implemented in Croatia, reflecting the changes made to water management legislation, aimed towards harmonizing it with EU standards and the requirements of the WFD. The preparation of a River Basin Management Plan in accordance with the WFD by Croatian Waters, in cooperation with the Ministry of Regional Development, Forestry and Water Management, is underway.
Bosnia and Herzegovina has established protection zones for drinking water supply for the Neretva Right coast aquifer (No. 130). Wastewater treatment plants exist in the area, but improvements are needed. Vulnerability mapping is planned for the Neretva Right coast (No. 130) and the Trebišnjica/Neretva Left coast aquifers (No. 131) in Bosnia and Herzegovina. Groundwater quantity is being monitored in the Neretva Right coast aquifer (No. 130) in Bosnia and Herzegovina, while groundwater quality is being monitored in Bilećko Lake aquifer (No. 132); improvements are, however, necessary in both cases. Data on Trebišnjica/Neretva Left coast aquifer (No. 131) has been exchanged between the two countries, but improvement is needed in this regard; enhanced monitoring is needed in both countries.
Monitoring of water flow and quality is being improved; more efforts are needed in the area of biological monitoring. This will allow the assessment of the status with regard to water supply, demand and quality, in a basin with a rather complex hydrogeology, providing the basis for adequate planning and regulation on a river basin level. The essential balancing of competing water demands, taking into account social, economic and environmental considerations, through a comprehensive and coordinated strategy agreed by the two countries, may follow. Enhancement of the national institutional capacity to plan, implement and enforce management measures on water demand and water use is indispensable.
Croatia reports that investments on flood protection and hydro- amelioration are necessary.
Transboundary cooperation
An agreement between Bosnia and Herzegovina and Croatia on Water Management Relations was signed in 1996, and is implemented through a joint commission, which is also the key bilateral mechanism for transboundary cooperation in the Neretva and Trebišnjica basins.
A Memorandum on Cooperation on the Neretva River was signed among Bosnia and Herzegovina, Croatia, the Principality of Monaco, and the Coordination unit of the Mediterranean Initiative of the Ramsar Convention on Wetlands (MedWet) in 2003. Pollution in the delta of the Neretva River, hydropower utilization, and water supply were among the priority themes.
In Bosnia and Herzegovina, the multiple levels of administration involved make coordination of international and bilateral cooperation challenging. This results in considerable delays in coordination, and difficulties in entering international agreements.
A GEF/World Bank project has been initiated with the objective to support IWRM in the basin, by harmonizing management approaches and legal frameworks across the two countries, and by ensuring improved stakeholder participation at all levels. The WFD principles and guidelines are used for what concerns the preparation of the river basin management plan. The Commission has been involved in the project preparation, and will oversee its implementation.
Trends
There is an accidental pollution risk due to the storage of large quantities of dangerous substances in the port of Ploce in Croatia, and their transport along the Neretva. Rural tourism is under development in Croatia; it may foster the reduction of pressures in the delta area of Neretva.
