Impacts of sea-level rise due to climate change on groundwater table in Whaiwhetu Aquifer, Lower Hutt, New Zealand

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Gregory Shahane De Costa, Marija Tutulic, Asaad Shamseldin

Friday 3 july 2015

13:30 - 13:45h at Europe 2 (level 0)

Themes: (T) Extreme events, natural variability and climate change, (ST) Flood resilient cities and infrastructures

Parallel session: 16I. Extreme events - Resilient

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Increase in groundwater table levels in coastal aquifers caused by sea level rise due to climate change is a very important and growing issue around the world. The development of effective tools and management strategies to investigate and possibly prevent and/or influence the impacts of this phenomenon is of the great importance for every urbanised area. This paper highlights investigation and the impacts of the changes in groundwater table caused by sea level rise due to climate change in Whaiwhetu Aquifer, Lower Hutt, New Zealand. The aquifer is located in coastal zone of almost completely urbanised area of Lower Hutt, north of Wellington City. The Whaiwhetu aquifer is very productive and it accommodates around 40% of Greater Wellington’s annual water demand. In the past 100 years sea level raised on average 0.2 m in Wellington region and it is predicted that by the 2090 sea level will increase by 0.8 m and by 2115 almost 1m (Bell and Hannah, 2012). This change inevitably will have impact on groundwater table in the Whaiwhetu Aquifer and it is of utmost importance to estimate it. Therefore an investigation has been carried out by developing a three-dimensional hydrodynamic numerical model. Numerical model was developed using comprehensive groundwater modelling package FEFLOW 6.1. Once the model was developed and calibrated, four “what if” scenarios regardless of the time period (Bell and Hannah, 2012), were investigated. Scenario 1 assumed the increase of 0.5 m of the mean seawater level (MSL). Scenario 2, Scenario 3 and Scenario 4 assumed an increase of 1.0 m, 1.5 m and 2.0 m MSL respectively. The changes were compared in nine observation bores and the results are presented.