To better understand hydrological processes relating to groundwater (link rainfall recharge blog), better estimates of all variables in the hydrologic cycle need to be made, including uncertainty estimates. One of the most elusive variables is evapotranspiration (ET): the amount of water that evaporates from soil or transpires from vegetation.

The SAC programme developed a new approach for the interpolation of sparse ground-based ET estimates with satellite data. This helps to better estimate ET and its uncertainty in New Zealand. The result is a nation-wide dataset of monthly 1x1km ET estimates. The resulting data can be used for several hydrological purposes by scientists or end-users from regional councils. Within the GNS led Smart Aquifer Characterisation Programme they will be used to estimate monthly groundwater recharge on a nation-wide scale.

Nation-wide evapotranspiration to monthlyl values Figure 1: Nation-wide evapotranspiration compiled to monthlyl values.

The data are available in NetCDF (see Table 1) and is described in detail in Westerhoff(2015)

(here could go little map from the SMART Mapviewer)

Table 1: Specifications of MOD16 ET data files for New Zealand

Info Spec
Format NetCDF UCAR (2014), CF-1.6
Spatial resolution 30 arc sec
Coordinate system WGS84 (EPSG:4326)
Start Jan-2000
End Dec-2013
Time interval Monthly
Unit mm/month
Data layers Monthly ET MOD160
- Uncertainty in MOD160
download Original MOD16 PET
download Original MOD16 AET


R.S. Westerhoff, 2015. Using uncertainty of Penman and Penman–Monteith methods in combined satellite and ground-based evapotranspiration estimates, Remote Sensing of Environment, Volume 169, November 2015, Pages 102-112, ISSN 0034-4257,