Illustration of the connectivity of water resources, including soil water, surface, and shallow groundwater. The yellow shows the hydrologically connected settings included in the physiographic approach, purple identifies settings that are excluded.
Physiographic Environments of New Zealand
The Physiographic Environments of New Zealand (PENZ) was a three-year project co-funded by Our Land and Water National Science Challenge and regional councils that links fresh water to the land. Understanding this relationship is crucially important as it is a major influence over water composition, and hence quality. For instance, landscape features can account for more than twice the variability in water quality than land use alone (Johnson et al., 1997; Hale et al., 2003; Dow et al., 2005; King et al., 2005; Shiels, 2010; Becker et al., 2014). For this reason, it is important to include landscape attributes in an attempt to explain ‘how’ and ‘why’ water quality varies across a catchment or region. The Physiographic Science turns existing thinking on its head because it uses the signals in water to trace the water’s journey through the landscape.
The project will use national and regional water composition and quality data sets in conjunction with existing geospatial layers to map the set of processes (hydrological and redox) that control the spatial variability of water. The method uses scientifically rigorous techniques to bring together data for climate, topography, geology, soils, and hydrological controls with analytical chemistry at a national scale. It will also be ground-tested using expert local knowledge. The resulting product will be “Physiographic Environments of New Zealand” – a freely-accessible, high-resolution map that explains the ‘how’ and ‘why’ water quality varies spatially. Below is an example of the hydrological settings included in the physiographic approach.
The method used in the project has been peer-reviewed both nationally and internationally (Rissmann et al., 2016). It was also ratified by Our Land and Water National Science Challenge, which has provided partial funding for the project. Unlike the crown research institutes and universities also involved in the national science challenges, this project is being developed out of an independent consultancy, and hence the need to obtain Regional Council support and funding to complete the project.
A key requirement of the PENZ programme has been to obtain co-funding from regional authorities throughout New Zealand, to facilitate application of the physiographic approach in as many regions as possible. It has been great to receive financial support from Northland Regional Council, Auckland Council, Bay of Plenty Regional Council, and Environment Canterbury. Physiographic mapping of the North Island resumed in early 2018, including the development of hydrological process attribute and redox process attribute layers. In addition, a high-resolution sediment layer is being currently being undertaken for Northland Regional Council.
For more information on this project contact Lisa (lisa@landwatersci.net)
References
Becker, J. C., Rodibaugh, K. J., Labay, B. J., Bonner, T. H., Zhang, Y., and Nowlin, W. H. (2014). Physiographic gradients determine nutrient concentrations more than land use in a Gulf Slope (USA) river system. Freshwater Science, 33(3): 731–744.
Dow, C. L., Arscott, D. B., and Newbold, J. D. (2006). Relating major ions and nutrients to watershed conditions across a mixed-use, water-supply watershed. Journal of the North American Benthological Society, 25(4): 887–911.
Hale, S. S., Paul, J. F., and Heltshe, J. F. (2004). Watershed landscape indicators of estuarine benthic condition. Estuaries, 27(2): 283-295.
Johnson, L., Richards, C., Host, G., and Arthur, J. (1997). Landscape influences on water chemistry in Midwestern stream ecosystems. Freshwater Biology 37(1): 193–208.
King RS, Baker ME, Whigham DF, Weller DE, Jordan TE, Kazyak PF, Hurd MK. (2005). Spatial considerations for linking watershed land cover to ecological indicators in streams. Ecology Applications, 15: 137–53.
Shiels, D. R. (2010). Implementing landscape indices to predict stream water quality in an agricultural setting: An assessment of the Lake and River Enhancement (LARE) protocol in the Mississinewa River watershed, East-Central Indiana. Ecological Indicators, 10(6): 1102–1110.