This repository contains hydrologic data collected at the Maimai Experimental Watershed in New Zealand, -42.0850, Latitude; 171.7960 Longitude (WGS84 Decimal Degrees). The purpose of this dataset is to bring together the data that has been collected over the past four decades and that has formed and shaped the collective understanding of rainfall-runoff processes at the Maimai. The readers is asked to refer to the published Data Note in Hydrologic Processes which highlights and describes these datasets, provides additional context in relation to the many peer-review manuscripts that have both developed and used these data. If these data are used, please cite this paper as:

McDonnell, J.J., C. Gabrielli, A. Ameli, J. Ekanayake, F. Fenicia, J. Freer, C. Graham, U. Morgenstern, T. Sayama, J. Seibert, M. Stewart, K. Vache, M. Weiler and R. Woods, 2020. The Maimai experimental catchment: Forty years of process-based research on steep, wet hillslopes. Hydrological Processes, in review.

This repository contains the following data organized by their layout in the HP Data Note. Please find citation references in the "Abstract References" PDF located in the Content folder below. References are provided for critical work associated with datasets for each phase of the Maimai study period.

Phase 1: Early M8 catchment-scale research and observations (1974-1988).
As noted in the paper, the Maimai experimental studies were initiate originally to investigate the hydrological effects of forest harvesting and radiata pine plantations in former native beech and podocarp forest. Thus the M8 watershed was first initiated as a paired watershed study together with several neighboring catchments down the Maimai valley. Gauging began in 1974 and we include in the data listed below rainfall-runoff information for the period Jan 1, 1975 – Dec 31, 1988. . The bulk of the data listed below is from the McDonnell PhD field work that combined hydrometric (tensiometer, well, trenchflow, rainfall-runoff) and isotope tracing. These data were collected through 1987 and reported how pipeflow of old water could occur and the nature of catchment-scale runoff generation as deduced from a combination of hydrometric, isotopic and geochemical analyses.
- M8 Streamflow from early Weir (3.8 ha catchment), Rainfall from upper and lower tipping bucket rain gauge (Jan 1, 1975 – Dec 31, 1988)
- M8 Streamflow, Rainfall, PET used in McDonnell 1990 WRR publication (09/87 - 12/87)
- M8 Isotope data for Rainfall and Runoff 1987
- Matric Potential from “Near Stream” site tensiometers (10/7/1987 – 11/17/87)
- Water table depth from “Near Stream” site tensiometers (10/7/1987 – 11/17/87 )
- Matric Potential from “Pit 5” site tensiometers (10/2/1987 – 12/17/87)
- Water Table Depth from “Pit 5” site tensiometers (10/2/1987 – 12/17/87 )
- Location and depth metadata for tensiometers installed at “Near Stream” and “Pit 5”
- Location and depth metadata for Suction Lysimeter.
- M8 DEM – 2 m, original DEM with 3.8 ha catchment prior to 1988 blowout

Phase 2: Hillslope scale trenching, forensic analysis and tracing (1993-2010)
Beginning in 1993, a major trench study was undertaken, as reported in Woods and Rowe (1996). They assembled a 110 day record of flow for 30 troughs of 1.7 m length in two groups across the base of hillslope section, some 10s of meters down valley from the current weir location. These data are listed below.
- M8 Hillslope Trench Discharge Data (1993)
- M8 Hillslope Tensiometer and Neutron Probe Data (Daily 12/23/1993 – 2/7/1994)
- M8 Hillslope Bromide Tracer Experiment – Trench flow and Concentrations
- M8 Hillslope Bromide Tracer Experiment – Water table data
- M8 Hillslope Spatial Survey Data

Phase 3: Drilling the critical zone: Bedrock groundwater dynamics, tritium age and its relation to stream flow and transport (2014-present)
The most recent phase of field data collection at Maimai was the period 11 December 2014 to 31 January 2016, representing 416 days of monitoring. This period was marked by a drilling campaign using a new field-portable drill rig specially designed for use at Maimai where 40 wells were drilled to a maximum of 10 m.
- Maimai DEM – 1 m Lidar based DEM of entire Maimai Experimental Watershed conducted by NZ Aerial Mapping Limited in 2014
- M8 DEM – 1 m Lidar Based DEM
- M8 Weir Location (Shapefile)
- Bedrock well locations
- Bedrock well water table location
- M8 Streamflow and Rainfall 2015