Oral Presentation Australasian Groundwater Conference 2017

Waituna Lagoon nutrient loads – a surface water or groundwater issue? (#195)

Clinton WF Rissmann 1 2 , Alexandra Badenhop 1 3 , Tony Weber 4
  1. e3 Scientific, Otatara, Southland, New Zealand
  2. University of Canterbury/Lincoln University, Invercargill, SOUTHLAND, New Zealand
  3. e3 Scientific, Arrowtown, Otago, New Zealand
  4. Alluvium, Brisbane

Waituna Lagoon is situated within the Awarua-Waituna wetland complex in Southland, New Zealand, recognised under the Ramsar Convention as a wetland of international importance. While the lagoon currently has significant biodiversity values; the majority of the catchment is intensively farmed, and natural and artificial drainage pathways rapidly route nutrient and sediment to the lagoon. The flipping of the lagoon to a hyper-eutrophic state is considered highly probable without effective intervention. However, it was recognised early on that a high degree of spatial variation in the nature of water quality outcomes despite very similar landuse pressures reflects steep gradients in physical hydrological and biogeochemical attributes. Therefore, the aim of this body of work is to identify how and why water quality outcomes and risk vary across the Waituna Catchment using a high-resolution physiographic approach. The physiographic approach uses the compositional signatures of waters to identify, map and classify the relevant attributes of the landscape that govern the processes controlling water quality outcomes. A temporal element has been added to the physiographic platform already developed for the Southland region, and attempts to answer such questions as “what contribution does baseflow make in terms of P flux relative to lateral soil drainage or overland flow?” and “do relative contributions from each flow path vary with time?”. Answering these questions is vital for sustainable primary production and enables the cost/benefits of water quality improvement controls to be optimised. Benefits of this approach include the use of pre-existing spatial information (e.g., national scale soil, hydrological and geological layers), which enables rapid and cost-effective application and provision of a visual-spatial depiction of the landform based controls over water quality outcomes that can be easily communicated to a range of stakeholders. By using pre-existing data this work integrates layers of information already available to obtain new insights.

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  • We are offering awards for Career and Early Career presentations and posters. Please indicate length of time since highest degree completed.: 5 Years or more