Data pertaining to 'Tauranga shallow groundwater monitoring, spatial observations and forecast conditions under sea-level rise'

Tauranga City in the North Island of New Zealand has many assets and infrastructure sitting on low-lying coastal land, where groundwater is unconfined and close to the surface. Shallow groundwater limits the volume of unsaturated ground available to store rain and runoff, promotes flooding and creates opportunities for infiltration into stormwater and wastewater networks. Groundwater levels are expected to rise as sea level rises, causing greater frequency of flooding and/or direct inundation once it nears the ground surface.  This zipped archive contains an ArcGIS 10.8 geodatabase generated from spatial analysis of data gathered from the Tauranga City Council's shallow groundwater monitoring network between 20/8/2015 and 13/8/2021. A series of statistical surfaces represent the 'present-day' water table elevation and depth to groundwater, and the response to tidal forcing.  Simple geometric models have been developed, following Cox et al. (2025 https://doi.org/10.1029/2024EF004977) methods, using the shape and position of the water table, combined with tidal fluctuations, to forecast the future state of median (p50), mean high water springs (mhws) and storm surge groundwater levels. Future forecast surfaces are provided at 10 cm increments of sea-level rise (up to 1 m), then 20 cm increments (from 1 to 2 m). The geometric models are strongly empirical, with many implicit assumptions and caveats – particularly, they do not account for groundwater flow and possible changes in water-budget mass balance. They assume groundwater will rise at the same rate as sea level, which is a ‘worst-case’ scenario (akin to a flux-controlled or recharge-limited end-member groundwater model). Although many variables and controlling processes are simplified into a single parameter of groundwater elevation, the projected groundwater levels highlight how local variations in water table shape and slope interact locally with the ground elevation or infrastructure networks. They are a first pass conservative analysis of groundwater-related contribution to hazard and how this will evolve over time. Data are provided under Creative Commons Attribution 4.0 (CC-BY-4.0) license without warranty. Further description of these data, and implications from the analysis, can be found in the metadata for individual layers and Cox (2025) GNS Science Report 2024/47 https://doi.org/10.21420/GDWW-6Z50.