History
City wastewater and agricultural run-off during a time of expanding urban population have played a substantial role in causing the ecological imbalance of Lake Rotorua and Rotoehu (Keddy, 2010). Before floating treatment wetland (FTW) implementation, both lakes suffered from nitrogen limitation and chronic harmful algal blooms (HAB’s). The detrimental effects decreased aquatic biodiversity, damaged world-renowned trout fisheries, and led to a dramatic decline in tourism (Burns et al., 2005; Burns et al., 2009; MacGibbon et al., 2010). In response, water quality managers learned to control harmful algal blooms using FTW’s (Tanner & Headley, 2008). Due to cost-effectiveness and low-impact, FTW’s are now considered to have a national importance in New Zealand (Burns et al., 2009; Kadlec and Wallace, 2008).
Set up under the Rotorua Te Arawa Lakes Programme, the floating wetlands initiative has two objectives. Firstly, planting twenty thousand native plants helping to improve Lake Rotorua water quality. Secondly, promoting the district with ‘Rotorua’ floating on the lake. It is estimated the wetland will remove up to four tonnes of nitrogen and more than a tonne of phosphorus from the lake yearly (Rotorua District Council, 2014). As the case study will make clear, environmental engagement is also a co-beneficial purpose of the FTWs. |
Map of Rotorua Lakes District, New Zealand.
Harmful Algal Blooms (HAB’s) covering Lake Rotoehu in the summer.
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