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Climate change effects on aquatic ecology and the future for stormwater management

This paper ‘Climate Change Effects on Aquatic Ecology and the Future for Stormwater Management‘, was presented at Water New Zealand’s 2017 Stormwater Conference. By Paul Battersby & Emily Jones (both from Opus International Consultants).

Climate change is predicted to have varying effects on the regions of New Zealand. The general effects in the eastern regions will be extended drought periods and decreased seasonal rainfall. In contrast, northern regions will likely experience more intense rain and storm events.
The environmental effects of climate change will be extended periods of low base flow during drought in the eastern regions and subsequent stress on aquatic biota. In Auckland, effects will be increased flash floods and seawater inundation of freshwater systems, with similar detrimental effects on aquatic species.
Regional and district plans are starting to give strong direction towards water-sensitive design and the requirement to improve the aquatic environment during stormwater management planning.
It is likely these statutory requirements will increase in the future. It is difficult to predict what the stormwater industry will be like post-2050 but it is obvious the nuanced effects of climate change will require adaptation and management, we are already seeing some of these effects.
In our full paper, we look at the likely environmental effects of climate change in two contrasting regions of New Zealand, how these will affect aquatic ecology and the implications for stormwater management.
Risks and opportunities to aquatic biota along riparian margins are discussed, with a multidimensional assessment of climate change impacts on aquatic species and its impact on the water quality in our waterways given.
Technical developments and potential tolls for adapting to climate change in New Zealand are also provided.
Some aspects of future stormwater management can be fixed by further refinement of standards such as GD04 for Water Sensitive Designs, GD05 for Sediment and Erosion Control in the Auckland region or the National Policy Statement on freshwater quality and quantity nationwide.
Nutrient and dissolved solids (DS) removal may be incorporated into stormwater standards in addition to the current total suspended solids (TSS) requirements.
Policies can be changed to focus on a more interdisciplinary approach that incorporates the concepts of green urbanism. The Auckland Unitary Plan is moving in this direction with a catchment scale focus and a focus away from ‘end of pipe treatment’.
New technology will play an increasing role in future decades. While at-source treatment will be the guiding strategy, it will be important to monitor downstream systems to ensure desired outcomes are being met. New technology such as artificial intelligence will play a critical role in getting better and more data than is feasible with current technologies.
Environment in design is a fundamental concept that is incorporated throughout Opus projects through the collaboration between different specialists, industry and regulators. We have adopted this to guide and educate the professionals in our company to address the future challenges while delivering the projects for our clients.
As an industry we need to look at how we provide guidance to practitioners to give consideration to options that have a better outcome for the environment.

This article was first published in the June 2017 issue of NZ Local Government Magazine.

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