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INTERNATIONAL COOPERATION ON WATER SCIENCES AND RESEARCHTranslation of solutions for AfricaEthiopia is one of the biggest countries of the Africancontinent with an impressive history and high potenment,20 was tested in Łód, Poland. The Blue-Green Network concept 21applies an ecohydrology approach at the city scale, connecting rivervalleys and green spaces. Such an approach helps to reduce stormwaterrelatedrisks without investing in costly hard (grey) infrastructure. Itimproves the microclimate and encourages healthy lifestyles by providingspace for recreation. The city also becomes resilient to global climatechange while its improved image attracts business, contributing toeconomic development.The Blue-Green Network concept was tested at a demonstrationriver, the Sokołówka, which is supplied by stormwater outlets,almost lacking natural flow. The middle section has maintained asemi-natural character, holding value for city inhabitants as an areaof recreation. The measures attempted to harmonize the river’s existinghydrotechnical infrastructure with the potential of its ecosystem,to enhance its capacity for absorbing increased water and pollutantfluxes without compromising its quality and appearance. 22A Sequential Stormwater Biofiltration System (SSSB), containingsedimentation, biogeochemical and constructed wetland zones,was constructed in the upper section of the Sokołówka. In the firsttwo experimental years of its operation, the system has reducedsuspended matter by more than 90 per cent and concentrations oftotal nitrogen and phosphorus by up to 60 per cent. 23 A detentionpond recently constructed upstream of the SSSB stabilizes the riverflow and further increases the system’s efficiency.A cascade of retention reservoirs was constructed on the river tomitigate extreme flows and hydrological stress. Shaping the reservoir’shydrodynamics and phytoremediation gave it the capacity to absorb theincreased nutrient loads without the appearance of toxic algal blooms.Rehabilitation plans were elaborated for the riverand Sokołówka River Park, to improve the ecologicalstatus of the river. This increased the capacityfor water retention, groundwater amelioration andvegetation growth and improved social access anduse of the area.Space and expertise were created through higher,pre- and post-doctoral education, awareness raising andtraining, empowered decision-making, fostering interinstitutionalcooperation for better water management 24and triggering several bottom-up initiatives, includingthe implementation of basin management plans in newinvestments and the participation of NGOs.Through these activities, the city authorities movedtowards restoring the quality of the city through anintegrated approach in which environmental rehabilitationand spatial planning are as importantas economical and social issues. The Blue-GreenNetwork concept was included in the Strategy ofIntegrated Development of the City of Łód, 2020+.Systematic rehabilitation of green and blue areasenables recognition and a closer association of environmentalheritage with the revitalization of thecity’s historical industrial architecture.The first stage of the implementation of the Blue-Green Network concept: Sokołówka river in ŁódSource: Wagner and Zalewski, 2009; updated[ 302 ]