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Stream health assessment tool developed to guide restoration efforts

A new study conducted at Reichman University's School of Sustainability presents an innovative tool to help decision-makers better understand the condition of streams and thereby advance their restoration and rehabilitation. The tool, called SESBI—the Stream Ecosystem Services and Biodiversity Index—is designed to measure what is called "stream health," meaning the degree to which a stream functions ecologically and contributes to public welfare.

When determining whether or not a stream is "healthy," it is not only the water itself that is taken into account, but also the diversity of animals and plants it supports, the quality of the water, the physical structure of the stream and its surroundings, and the stream's capacity to handle floods, purify water, and provide recreational opportunities.

What sets the SESBI apart from other indexes is that it evaluates the stream's ecological condition based on the services it provides to people—rather than the other way around. If people can swim in the stream, walk along its banks, and enjoy the scenery, and if the stream is able to purify itself and mitigate floods, these are strong indications that it is functioning well.

The idea behind the SESBI is to make the subject of stream restoration accessible even to those without ecological expertise. The index is based on available or easily obtainable data, and presents a relatively clear and simple assessment—using a scale of 1 to 10—enabling decision-makers to quickly understand the stream's condition, identify specific problem areas, and prioritize investments of effort and budget.

Instead of relying on complex chemical or biological tests, the SESBI uses six indicators directly tied to the benefits streams provide: biodiversity, water purification, the quality of the vegetation around the stream, enjoyment derived from the landscape, recreational activities, and the stream's ability to cope with floods.

In addition, the index was developed specifically for streams in Mediterranean and arid regions, such as Israel, where there are extreme seasonal changes between winter and summer, and streams may flow only during certain times of the year. Existing indexes are generally designed for large rivers in Europe or North America, and are not suited to Israel's completely different hydrological regime.

The study, led by doctoral student Geula Michael-Bitton under the supervision of Dr. Shiri Zemah-Shamir and Prof. Boris Portnov from the University of Haifa, tested the index on three streams in Israel: the Na'aman, Yarkon and Kishon. The health scores obtained were 6.38 for the Na'aman, 6.06 for the Yarkon, and 4.47 for the Kishon—with higher scores indicating healthier streams and a greater variety of services provided.

The goal is to enable smarter planning and management of water and natural resources in Israel. The index also lays the groundwork for future development, where it will be possible to translate the contribution of each stream into economic terms—for example, illustrating the benefits that the public and authorities gain from investing in stream restoration. Looking ahead, the researchers hope to expand the index to include additional social, economic, and spatial dimensions.

According to Dr. Zemah-Shamir, "The new index allows us to view streams not only as natural infrastructure, but as sources of real benefits for humans—such as shade, cooling, opportunities for hiking and picnicking, and reduced flood damage. In an era of climate change and water scarcity, this is an essential tool to support wise decision-making that preserves both nature and our quality of life."