Restoring Water Balance on Utö – A Pilot Area for Smarter Water Management

A key component of the WSSP project is to initiate conducting pilot-scale remediation activities in the participating countries to demonstrate effective and scalable solutions for runoff management in a changing climate. On the island of Utö in Sweden, a new system of small forest wetlands is helping to stabilise water flows, support fish migration, enhance biodiversity, and protect the Baltic Sea.

Utö is a small island in the southern Stockholm archipelago, surrounded by the Baltic Sea. The pilot area is located in the northern forest of the island, where rainwater naturally collects and flows down through a stream into the coastal wetland of Södra Fladen. This area is especially important because it supplies fresh water to the coastal ecosystem and serves as a migration route for predatory fish in spring.

Changes in rainfall cause problems for fish and local wells

As part of the WSSP project, Royal Institute of Technology (KTH) together with Initiativ Utö seeks to develop and implement practical, resource-efficient approaches to mitigate diffuse pollution and stormwater management affecting the Baltic Sea. Utö, as many other places, has experienced clear changes in rainfall in recent years: heavy rain in winter and almost no rain in spring. This creates several problems. The stream running from the forest dries out during April and May, making it difficult for fish to reach their spawning grounds. Local wells are also affected as groundwater levels drop, and the coastal wetland receives too little fresh water. Because of these challenges, and because Utö already works actively with wetlands and environmental monitoring, it is a very relevant location for testing new water-saving solutions in real conditions.

Water protection measures implemented on Utö

During 2024 and 2025, six small forest wetlands (dams) were constructed in a connected system along the natural water pathway. Their purpose is simple: to hold back water during autumn and winter, or during rainfall, and release it slowly during spring. By saving water in this way, the stream remains active longer, which helps migratory fish reach the coastal wetland to spawn.

These wetlands also create calmer and more stable conditions in the forest, benefiting plants, insects, birds and amphibians. In the ditch and coastal wetland below, more steady water flow supports overall biodiversity.

To better understand how the water changes over time, samples have been taken every month since May 2024 at nine different locations between the forest and the sea. Three real-time sensors will be added in 2025 to continuously measure water levels and quality.

In the next stage, planned for 2026, selected wetland plants will be introduced. These plants can absorb certain substances from the water before it reaches the Baltic Sea, adding a natural filtering function.

A model for other coastal areas

The pilot area on Utö shows how small, nature-based measures can help solve local water challenges caused by climate change. It also demonstrates how monitoring, simple engineering and ecological knowledge can work together. The experience gained here may be used as a model for other islands and coastal regions facing similar problems in the Baltic Sea area.