National gravel bed river project’s final findings out

Groundbreaking national research on how braided rivers such as the Wairau interact with groundwater systems including the Wairau Aquifer is complete.

The report’s findings were presented to Council’s Environment and Planning Committee recently.

Senior Environmental Scientist Groundwater Peter Davidson said the study - which looked at the Wairau, the Ngaruroro in Hawke’s Bay and the Selwyn/Waikirikiri in mid-Canterbury – had its origins in Marlborough as part of work to understand the long-term trend of decline in Wairau Aquifer levels.

“We are focussed now on how we can apply the research. It will be a valuable piece of work for the upcoming review of the Lower Wairau River Scheme and the sustainability of gravel extraction volumes through the Gravel Extraction Strategy,” Mr Davidson said. “Under the Marlborough Environment Plan the Wairau Aquifer needs to be managed to maintain spring flows. Council manages the river to provide recharge to the aquifer which in turn maintains the springs.”

The effect of the decline in aquifer levels was often felt over summer with a flow-on effect to the springs on the plains, Mr Davidson said. “Council is working on the causes of this - some we can regulate and some we cannot.”

Funded by the MBIE Endeavour Fund with contributions from Marlborough District and Hawke’s Bay Regional councils and Environment Canterbury, the four-year study was carried out by Lincoln Agritech and was a cross-council collaboration involving the Rivers, Policy and Environmental Science teams.

Rivers and Drainage Engineering Manager Andy White welcomed the report. “My key takeaway is we need to move away from seeing flood management as an independent activity to viewing it as part of a whole river system,” he said. “The most appropriate way to do this is through the upcoming Wairau River Scheme Review.”