(12)Those plans should include measures to reduce the pollution from storm water overflows and also address the potentially significant pollution coming from separately collected urban runoff, for instance the pollution resulting from first rains after long dry periods in densely populated areas. Those plans should also include measures to prevent pollution at source and favour nature-based solutions over those that would require the establishment of grey infrastructure. Those measures could include preventive temporary measures aimed at avoiding the entry of unpolluted rain waters into collecting systems or temporary storage, including natural water retention, and appropriate treatment of heavily loaded runoff or overflows resulting from first rains. Member States are encouraged to increase green and blue spaces in urban areas and to take into account the Urban Nature platform, which provides guidance and knowledge to support towns and cities. In order to ensure adequate coverage of the integrated urban wastewater management plans and a comprehensive solution to storm water problems, those plans should be established for drainage areas of the agglomerations concerned.