Natural Water Retention in the Ramabujas Stream

The road to water retention in the Ramabujas catchment

On September 3, 2023, heavy rainfall caused flooding in central Spain. An earlier quickscan of the watersheds around Toledo showed that water retention is poor and runoff is rapid, leading to extreme flood peaks downstream. Combined with the dense urban development of the river valleys, this results in serious problems and fatal risks. 

One of the impacted companies was Suntory, who commissioned Stroming, in collaboration with the University of Toledo and Wetlands International, to conduct a detailed study of the water management of the Ramabujas watershed. The follow-up question was how to make the area more resilient to extreme weather events, such as floods and prolonged droughts. Since Suntory aims for full compensation for its water usage (~800,000 m³/year), we investigated which natural measures could enhance the area's water retention capacity.

The main conclusion is that the area's water retention capacity is very low due to intensive, unsustainable land use. Olive groves are kept completely free of undergrowth, fallow fields are regularly ploughed to meet EU Common Agricultural Policy (CAP) conditions, and even well-used fields remain bare for much of the year. This lack of vegetation means rainwater hardly infiltrates and primarily runs off quickly, leading to erosion, loss of fertile soil, and increased flood risks downstream.

The soil as the driving factor to a natural sponge landscape

The main recommendation is to stop ploughing as much as possible and to introduce year-round vegetation cover. For several upstream sub-areas, we present plans that protect the soil, enhance rainwater infiltration, or slow down its runoff. This can be achieved by transforming current land use into more sustainable practices or by converting the most vulnerable fields into natural habitats. Water retention areas along the Ramabujas provide space for runoff during high water, promote additional infiltration, and can also be used for recreation by the local population. The results are summarized on the digital website.