Szigetköz region-revitalization of the ecological system

Organization: SZE - Széchenyi István University (Hungary)

The Szigetköz water replenishment system has been set up and is operated in collaboration with stakeholders to dynamically control discharges and restore natural water levels on a 40 km-long active and historical floodplain river branch system along the Danube, thereby creating diverse habitats while promoting ecological connectivity through fish passages.

General info

The "inland delta" of Szigetköz features a unique floodplain ecosystem formed by the Danube's natural fragmentation into multiple parallel river branches. This diverse ecosystem supports numerous species of fish, birds, and mollusks.

In the 19th century, channel alterations were made to improve navigation and flood protection, while hydropower construction in the mid-late 20th century diverted water from the main channel, leading to a significant drop in surface and groundwater levels and drying up many branches.

The Szigetköz Water Replenishment System was designed to counteract these changes by restoring natural water levels across a 40 km stretch of the Danube floodplain. Stakeholders actively participated in planning the system, which operates eco-friendly and without electricity, dynamically controlling flows to recreate authentic water conditions. This restoration effort has created diverse habitats, enhanced ecological connectivity through fish passages, and improved water use opportunities.

What measures have been taken

The system was established with a holistic view of planning, design, construction, and management.

Planning: Stakeholders prioritized flood control for the safety of settlements and the region. Following this, they focused on maintaining drinking water supply, nature conservation, fishing, forestry, and tourism. Engineering designs aimed to achieve these goals in the fragmented floodplain while ensuring desirable ecological conditions.

Design and Construction: A dynamic water replenishment approach based on the Danube's natural flow patterns was implemented. Target water levels were set using conditions from the 1950s and 1960s, with hydraulic controls designed to replicate historical flows. Key structures like the Dunakiliti Dam and a submerged weir facilitate a gravitational distribution system to restore surface water levels. Fish passages were built to reconnect separated water bodies, enabling natural flow conditions across the floodplain.

Operation and Management: The Szigetköz Operating Committee, including representatives from various sectors, oversees operations and considers stakeholder modification proposals. The Committee can initiate artificial flooding in spring to mimic natural flood levels, supporting the vegetation period. This inclusive approach, involving "bottom-up" community participation, ensures proactive and locally appropriate solutions for successful floodplain restoration.

Activities within the DALIA project

Within the framework of the DALIA project, Széchenyi István University is undertaking the following activities:

• Research Activity - Quantifying Benefits with Stakeholders
• Knowledge Transfer – Replication of Site Guidelines, Manuals, and Consultation
• Educational Materials – For Local and Wider Public

Environmental Impact

• Positive Environmental Changes: Water replenishment systems following the Danube diversion have revitalized natural water ecosystems and improved conditions for aquatic habitats, forestry, agriculture, and ecotourism.
• Improved Water Levels: Both surface and groundwater levels have risen above pre-diversion conditions, with surface water levels in the active floodplain matching those from the 1950s.
• Biodiversity Restoration: The water replenishment system has restored the biodiversity of the Szigetköz river branch system, with many fish species returning to the area.
• Forest Growth: The diversion initially impacted forest growth negatively, but artificial floods and major flood events have positively influenced forest health, demonstrating the importance of water dynamics.
• Agricultural Recovery: In central Szigetköz, water replenishment efforts have helped restore crop yields to nearly previous levels after an initial decline due to lowered groundwater levels.
• Boost to Ecotourism: The restoration of floodplain branches has boosted ecotourism, evidenced by an increase in camping sites and canoe rentals in the region.

Recommendations

The Szigetköz water replenishment system, a collaborative project, has successfully restored natural water levels and dynamically controlled discharges in floodplain river branch systems, improving a 40 km stretch of the Danube. This effort has created diverse habitats and promoted ecological connectivity through fish passages. Addressing the needs of diverse stakeholders can lead to conflicts, best resolved through a bottom-up, interactive planning process that facilitates compromise.