Proponents of a new generation of decentralized urban water management practices claim that the negative impacts of urbanization on terrestrial and aquatic ecosystems can be significantly reduced with improved planning and design at the individual land parcel level, even in densely populated urban watersheds. The historical “mechanistic-hydrotechnical approach” to water resource management (Zalewski 2000) was successful at resolving many pollution problems at the end-of-pipe. However, it failed to “solve” environmental problems because it ignored the role that biotic and abiotic regulators found on upstream catchments play in determining overall environmental quality. Historical land use change caused extensive modification to local, regional, and global energy and water balances, proliferation of non-point sources of pollution, changes in atmospheric composition, loss of biodiversity, and possibly modification of the climate system itself (Foley et al 2005).
These new decentralized water management practices, known alternatively as low impact development (LID), stormwater best management practices (BMPs), or green infrastructure (GI) seek to mitigate the impacts of urbanization by “mimicking” natural hydrologic processes on individual development sites using various water harvesting, infiltration, and reuse practices. Substantiation of these claims requires significant advances in urban hydrologic modeling capabilities. Specifically, the ecosystem impacts of such technologies can only be assessed if an accurate means of predicting how these interventions would affect a wide range of environmentally critical flows (e.g. across the atmosphere/surface and surface/subsurface boundaries within the watershed) can be quantified and compared to some relevant urban baseline condition. Such predictions need to take into consideration the non-linear effects of multiple, decentralized interventions potentially implemented across very wide geographic areas.
SWRE researchers are involved in several efforts to develop new tools for assessing the impacts of decentralized green infrastructure approaches to urban water management. This work involves developing computer simulations and collecting data that will help to quantify the multiple benefits of technologies like permeable pavements, green roofs, rainwater capture, storage, and reuse, bioinfiltration, when they are implemented at various scales in urban watersheds.