104-13 Volcanic Hosted Groundwater System Dynamics: Influence of Vegetation Cover on Soil Moisture and Infiltration

Session: A Showcase of Undergraduate Research in Hydrogeology (Posters)

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Abstract:

The rate of rainfall infiltration and resulting groundwater dynamics are heavily influenced by vegetation cover, precipitation, and climate. Within Rāpaki Valley, Banks Peninsula, New Zealand, there are two main types of ground cover: native vegetation and exotic pastoral grass. These ground covers lie above a volcanic-hosted spring system, where rainfall infiltrates at the Recharge Zone, feeding into the groundwater-fed Spring Seep Zone. The factors influencing rainwater infiltration into the subsurface groundwater system in Rāpaki Valley have yet to be explored. Here we show that native vegetative ground cover in the recharge area promotes a more stable, continuous infiltration rate and groundwater input to its spring than grass cover by using measured soil moisture and rainfall data. This study found that vegetation cover has an important role in determining the volumetric water content within the soil, and areas with increased indigenous vegetation cover tend to have higher water content throughout the year. Results illustrate the importance of restoring native vegetation in Rāpaki Valley. While our findings are important in a cultural and historical context, they are also crucial to sustaining the area's ecological health, especially in a changing climate. Te Hapū o Ngāti Wheke is actively restoring the native vegetation and supporting ecosystems to bring life back to the awa (waterways). Greater knowledge of the subsurface groundwater system and the connections between ridges and valleys can support restoration efforts in areas relevant to these waterways. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9897

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