'Gornji Horizonti' and reduced water flow threaten Neretva ecosystem

The 'Gornji Horizonti' project, a significant component of the Trebišnjica hydrosystem, is raising alarms in Croatia as it diverts water from the Neretva River basin for electricity generation. This diversion is altering the natural water flow and reducing freshwater inflow into the lower Neretva, a region vital for agriculture and ecological stability. Croatia, deeply concerned by these developments, is highlighting the transboundary implications of such large-scale water management projects.

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The 'Gornji Horizonti' are an integral part of the wider Trebišnjica hydrosystem, whose foundations were laid in the mid-20th century and further developed in later projects, and which is now entering a new phase of implementation with a series of hydroelectric and water management interventions in eastern Herzegovina.

Croatian experts and institutions, including the Croatian Academy of Sciences and Arts in Bosnia and Herzegovina, are emphasizing that water management in shared basins is no longer solely a technical issue but a matter of national responsibility. Based on experiences with existing systems and its own international initiatives, Croatia is advocating for a cautious approach. The focus is not just on energy production but on safeguarding water as a fundamental resource essential for the survival and development of the Neretva valley.

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The logic of this system involves diverting part of the waters from the Neretva basin towards Trebišnjica for electricity production, which is why its effects do not stop at the point of intervention but are transmitted downstream, including the lower Neretva in Croatia.

The impacts of the already constructed parts of the Trebišnjica system are evident. Studies and monitoring have confirmed changes in the water regime, including reduced groundwater recharge and altered underground water flows. The Hutovo Blato action plan, for instance, documents significant environmental changes, such as the creation of an artificial water regime and a substantial decrease in water inflow. This has led to a decline in bird species and the loss of over half the water sources in the area, illustrating how changes in one part of the system cascade into others, particularly in karst environments where such impacts are amplified and spread downstream.

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Are the consequences of the already built hydrotechnical system on Trebišnjica and the connected parts of the Neretva basin unequivocally confirmed today? To a significant extent, yes, and that is the starting point of the Croatian position.

This situation underscores the interconnectedness of water resources in the region. The Neretva River, flowing through both Bosnia and Herzegovina and Croatia, serves as a critical artery for ecosystems and human activities. The 'Gornji Horizonti' project, by altering its flow, poses a direct threat to the delicate balance of the Neretva delta and its surrounding areas. Croatia's concerns are rooted in the scientific evidence of environmental degradation and the potential economic repercussions, urging for responsible decision-making that considers the long-term sustainability of this vital watercourse.

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The action plan for Hutovo Blato notes significant changes in the natural environment, including the creation of an artificial water regime and reduced inflow, and available data show that the number of bird species in the area has decreased by about 30 percent since the 1970s, with the loss of more than half of the water sources associated with the development of the hydroelectric system in the vicinity.