To better manage freshwater pollution, we need to understand the pathways by which nitrogen travels from the land to waterways, how fast it travels, and how much nitrogen is naturally removed by microorganisms as it moves from the soil through the groundwater into a waterway.
At present, there is little understanding of these transport and transformation processes at the sub-catchment scale (10s of km2). However, knowledge at this spatial resolution is needed to protect the water quality in the many local streams that feed the typically monitored rivers (with catchment areas often 1000s of km2). This missing information makes it difficult for land-users and regulators to make effective and efficient land-use and land management decisions and choose appropriate mitigation options.
Lincoln Agritech is leading the Critical Pathways Programme (CPP), a research programme funded by the Ministry of Business, Innovation and Employment (MBIE), to respond to this well-recognised knowledge gap. This five-year research programme has started to elucidate the relatively shallow and short pathways operating at the sub-catchment scale, and to represent them in water flow and contaminant transfer models.
The programme is introducing significant innovations in hydrogeophysical data acquistion, ‘big data’ analysis, and water flow and contaminant transport modelling.
Working in collaboration with iwi, regional councils and industry, the research team will deliver:
- A range of tools and methods, using new geophysical measurements, that describe the subsurface contaminant pathways within a sub-catchment.
- Novel models that use this information to reliably predict the quanty of contaminants entering a waterway.
- Methods that enable soil and subsoil contaminant delivery characteristics to be estimated over large areas by relating them to geophysical measurements.
- Cost/benefit analyses that determine the most effective option to achieve a desired environmental benefit.
Informed by previous research and in consultation with our stakeholders, two intensively farmed catchments with contrasting hydrological and biogeochemical conditions were chosen as case studies:
- The Waiotapu Stream catchment on the North Island’s Central Plateau represents a baseflow-dominated upland catchment with large groundwater reservoirs in young volcanic deposits.
- The Piako River headwater catchment is a lowland catchment in the upper part of the Hauraki Plains with aquifer deposits of lower transmissivity and a large quickflow fraction in the river hydrograph.
The results of this study will help guide New Zealand regional councils and their collaborative stakeholder groups in their decision-making processes; and help them comply with the limits set by the National Policy Statement for Freshwater Management. All councils are required to have a policy for water quality management in place by 2025.
Led by Lincoln Agritech, the multidisciplinary research team includes experts from GNS, Manaaki Whenua Landcare Research, AquaLinc, Lincoln University, AgFirst, and IK & Associates.
Strong international collaboration occurs with the Technische Universität Dresden (Germany) and the Danish MapField programme. led by the Geological Survey of Denmark and Greenland (GEUS) and Aarhus University.
Further support is provided by Waikato Regional Council, DairyNZ, and the iwi holding mana whenua over our pilot catchments (Ngāti Tahu – Ngāti Whaoa, Ngāti Hauā).
To learn more about the project, click on the links below: