https://doi.org/10.1002/hyp.14112

McDonnell, J. J., Gabrielli, C., Ameli, A., Ekanayake, J., Fenicia, F., Freer, J., ... & Woods, R. (2021). The Maimai M8 experimental catchment database: Forty years of process-based research on steep, wet hillslopes. Hydrological Processes, e14112. doi:10.1002/hyp.14112

Many of our legacy research and observation catchments were developed during the First
International Hydrological Decade (IHD) (1965-74)—a period of intense catchment
gauging/instrumentation and arguably the beginning of serious process hydrology. The IHD
helped our science move beyond the era of infiltration (Beven, 2020) and towards an era that
recognized subsurface contributions to runoff via subsurface stormflow.
The year the IHD ended the Maimai experimental catchment(s) were initiated in New Zealand
(Figure 1). These studies investigated originally the hydrological effects of forest harvesting and
radiata pine plantations in former native beech and podocarp forest but quickly morphed into a
long sequence of runoff process investigations. Maimai has slopes that are short (<30 m) and
steep (mean 34O) with local relief on the order of 100-150 m. Maimai showed that subsurface
stormflow was by far the major contributor to storm runoff with chronically wet soils, with 156
rain days per year (Rowe & Pearce, 1994). Pearce, Stewart, & Sklash et al. (1986, p.1266)
notes that “mean annual gross rainfall is approximately 2600 mm, producing approximately
1550 mm of runoff from 1950 mm of net rainfall [Rowe, 1979]. The catchments are highly
responsive to storm rainfall: 1000 mm (65%) of the mean annual runoff is quick flow (QF) as
defined by Hewlett and Hibbert’s [1967] separation method [Pearce & McKerchar, 1979]. Quick
flow is 39% of annual total rainfall (P).”
Here we outline the data that underpins many of the studies from three main field
instrumentation and sample collection phases: (1) early M8 catchment-scale research and
observations (1974-1988), (2) hillslope scale trenching, forensic analysis and tracing (1993-
2010) and (3) drilling the critical zone with a focus on bedrock groundwater dynamics, tritium
age and its relation to streamflow and transport (2014-present). We describe the data series
and provide a link to an online repository of these data in Hydroshare at
https://www.hydroshare.org/resource/a292cb65a5d24a31a60978b2ab390266/ .

Core Modelling & Forecasting Team

https://doi.org/10.1002/hyp.14112