Modelling aquifer recharge with stormwater in urban areas

Abstract

Urban aquifers have potential for supplying cities with water. Urban development affects both quality and quantity of groundwater recharge and increases flood risk from urban stormwater runoff. Many studies show that traditional stormwater management has failed to mitigate the negative effects of urban expansion. Recently, the Low Impact Development (LID) approach has been advocated both nationally and internationally, as a sustainable approach for stormwater management. This approach uses distributed, decentralized source controls to manage stormwater runoff. This project explores groundwater aquifer recharge using stormwater as a possible LID option. The aim of this paper is to explore risks associated with aquifer recharge using stormwater, concentrating on changes in groundwater levels. The research site is in the Northern Strategic Growth Area, west of Auckland. The bedrock is Waitemata Group rocks, a complex structure of many alternating layers of mudstone and sandstone and localized extreme deformations. A two layer transient model was built using the three-dimensional finite-element software package FEFLOW 6. The first layer represents a shallow alluvium aquifer and the second layer represents the deep sandstone aquifer.