FRESHWATER MANAGEMENT TOOL - OUTCOMES AND LESSONS FROM TRADING COST FOR COMPLEXITY
Stormwater Conference 2023
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T. Stephens, T. Kpodonu, P. Nowell, M. Patel, N. Brown (Healthy Waters, Auckland Council), D. Bambic (Paradigm Environmental Ltd), H. Judd and C. Clarke (Morphum Environmental Ltd)
ABSTRACT
Auckland Council’s Freshwater Management Tool (AC-FWMT) is a decision-support tool, to inform how to maintain or improve water quality in urban and rural streams.
The AC-FWMT is based on open-sourced, continuous and process-based US-EPA models (LSPC+SUSTAIN). LSPC+SUSTAIN approaches are also under development in Northland and Bay of Plenty. Though differing in scale, resolution and purpose the accounting frameworks provide decision-makers with integrated, objective-based[1] information on waterway health, including contaminant and flow regime (existing, future); causes (sources, process); costed actions to maintain or improve water quality (least cost, feasible).
The AC-FWMT simulates hydrologic and contaminant processes on-land and instream, for 15-min timesteps, from mountains to sea in an approach informed by the National Policy Statement for Freshwater Management 2020 (NPS-FM) (see prior StormwaterNZ abstracts – Stephens et al., 2020 & 2022).
Now, the AC-FWMT can produce Waterway Action and Investment Strategies (WAIS) – geospatial, cost and water quality information on feasible actions of least cost for water quality objective(s). WAIS provide cost distribution across intervention type, catchments, parties and lifecycle phases. WAIS are precursors to the water quality improvement plans that provide detailed catchment planning priorities on a sub-catchment basis but for integrated water quality objectives.
Our talk will reveal how minimizing implementation costs has required increasingly complex modeling in Auckland, creating challenges for appropriate extension, use and continuous improvement of modelling. Challenges come with risk and reward, in our instance providing new data, insights and evidence of how to manage water quality better.
[1] Objective used in a regulatory/planning context of the NPS-FM, Resource Management Act 1991 (incl. ongoing revisions adopting NPS-FM). Examples include contaminant attribute states under the National Objective Framework that require improvement in numeric measures (concentration, load, flow) to within desired levels of some value (e.g., ecosystem health, human health).