Due to a combination of their largely impermeable nature (generates stormwater runoff), limited green spaces (reduced opportunities for infiltration and evapotranspiration) and ageing drainage infrastructure (piped systems are expensive and disruptive to excavate) this has major implications for urban areas. However, warmer summers will also increase rates of evaporation, contributing to an increasing number of low flow days in rivers and drought events. Hence, the same urban areas could face an annual increase in both flooding and drought events. In this challenge context, the role of stormwater generated in wetter months to provide an alternative water resource to mitigate summer droughts is receiving increasing attention.
The infiltration of stormwater to groundwater presents an opportunity to store and reuse water as a valuable resource in a manner that is internationally recognised as a best management practice for stormwater quantity and quality control. However, urban stormwater quality is characteristically highly variable in terms of both quantity and – crucially - quality in response to catchment factors (e.g. building materials, activities and land use) and rainfall patterns which can vary on a catchment by catchment basis. In the absence of complete data sets, current levels of uncertainty over stormwater quality and the processes that mediate its behaviour (i.e. remove or transform pollutants) as it infiltrates to groundwater has led to some municipalities ruling out this management option (and associated benefits).
In this FORMAS Blue Innovation project, we will work in partnership with Norrvatten to develop a community of practice focused on the role of stormwater blue-green infrastructure in the sustainable management of groundwater resources. A review of international studies relating to the infiltration of stormwater to ground and its impacts on groundwater quality will be undertaken, and findings used to inform a series of five discussion workshop on groundwater/stormwater management treatment options, the development of regional practitioner guidelines and evaluation of their national implications.