Peatland surface oscillation at two dairy farms on Moanatuatua drained peatland

Report: TR 2021/09

Authors: Georgie Glover-Clark and David Campbell (University of Waikato)

Drained peatlands are associated with major environmental and land management issues, such as the long-term irreversible subsidence of the peatland surface.

Shrinkage, a mechanism of subsidence caused by a shrinking of the peat matrix during dry conditions, is partially reversible upon rewetting, leading to seasonal oscillations of the peat surface height. However, rates of subsidence of drained peatlands have rarely been measured using high-frequency measurements able to discern peat surface oscillations, despite its potential to bias long-term subsidence estimates.

We measured the temporal variability of peat surface oscillation using paired pressure transducers at two adjacent dairy farms on Moanatatua drained peatland over a 17-month period, extending a previously reported 10-month dataset at the same study sites.

Reversible oscillations were 65.2 and 103.6 mm at the two sites, these exceeded most other published values in the international literature. Furthermore, oscillations were between 3.4 and 5.4 times greater than the average annual irreversible subsidence rate for the Waikato region, highlighting the importance of high-frequency measurements to separately consider reversible and irreversible subsidence processes.