Theme 2: Sources and Flows

Rationale

Different soils, landscapes and water pathways vary at a range of scales in their propensity to yield, convey and attenuate contaminants. For example, the amount of nitrogen that is naturally attenuated is highly dependent on whether runoff flows via shallow or deep groundwater pathways, and the biogeochemical conditions along these pathways and at the land:water interface 1, 2. Thus different sources and flow paths can substantially influence the quantity, and temporal and spatial patterns of contaminant loss from catchments. Our best current estimates suggest that on average around 55% of nutrients lost from productive land uses in New Zealand are attenuated as they make their way through catchments to the sea 3, but as also found elsewhere 4, 5 the proportions attenuated vary widely across and between landscapes commonly ranging from less than 20% to over 80%. The lands suitability for various types and intensities of land use can then be defined by combining this knowledge with information on the lands inherent productive capacity and the sensitivity or resilience of associated receiving waters (addressed in the Suitability Programme).

In general, attenuation rates are estimated as the difference between modelled estimates of contaminant sources and monitored and modelled estimates of loads exported from catchments. There can be large uncertainties in both these estimates 6-11. Different apparent attenuation rates can thus be due to the following: Firstly, the amount of contaminants lost from landuses in the catchmentcould be being over- or under-estimated. Secondly, the estimated catchment loads exported could be incorrect; e.g. due to calibration of models based on regular monthly monitoring of water quality which tends to miss high-flow events 7. Thirdly, apparent attenuation may actually be due to lag times in delivery, such that the current levels of contaminant delivered at the bottom of the catchment are from historically lower contaminant losses than are being lost from current land-use 12-14. Fourthly, genuine attenuation could be occurring along different flow paths by a range of processes, such as anoxic conditions promoting denitrification in groundwaters and/or organic-rich riparian zones and wetlands 1, 2, 15-18, trapping of sediment and particulate phosphorous in riparian buffers, wetlands, ponds and lakes 19, 20, or slow river flows and exposure to sunlight promoting uptake of nutrients 21, 22 and increased die-off rates for faecal microbes 23.

Knowledge of key attenuation pathways, rates and processes across landscapes provides the opportunity to: 1) establish the magnitude of contaminant sources and losses relative to natural baselines 24, establish the productive headroom available within a catchment, including locations with low or high contaminant loss, attenuation capacity and/or off-site pollution risks (as assessed in the Suitability Programme); 2) allow accurate limits to be set on land uses (i.e. contaminant sources) under the National Policy Statement of Freshwater Management (NPS-FM) to safeguard the life-supporting capacity of freshwaters and the associated health of people and communities; and 3) identify the critical contaminant pathways at the enterprise and catchment scalewhere different land-uses and management practices, and mitigation investments can be most cost-effectively targeted. This knowledge will provide options for productive enterprises to adapt and tailor their land use and management practices to work within the natural and engineered attenuation capacity of their landscape.

Recently a number of related approaches to diffuse pollution management that take into account pollutant transport pathways have been initiated by other research groups overseas 25-27. Our approach in the present programme, while incorporating relevant learnings from these studies, is distinguished in-particular by addressing multiple contaminants, our focus on exploiting natural and engineered attenuation capacity along transport pathways, and integration within the wider social, cultural and value-chain context of the OL&W Challenge. Many of these international programmes also address wider implications of contaminant pathways and fluxes, including greenhouse gas emissions and the biodiversity of agricultural ecosystem, which are beyond the current scope of the OL&W Challenge, or have a more central focus on assessing the consequences of climate change.

Aims or hypotheses

Key flow pathways and contaminant fluxes in the landscape can be identified and mapped to inform suitability for land use and response at multiple spatial and temporal scales.
Production (or profit) per unit of contaminant loss can be increased by considering the suitability of a land use, mitigation strategies and maximising attenuation along transport pathways.
When managed according to hypothesis 2 we will be able to identify scope for intensification without breaching a limit, identify constraints where new technologies or primary production systems are required, or where re-design of enterprises is needed.
Knowledge of flow pathways of contaminant fluxes can be used to identify if strategies to mitigate at the source of contaminants or along transport pathways will deliver better social, cultural, economic and environmental outcomes than intervening in receiving environments (viz. Suitability programme).

Objectives

Assessment of catchment source and delivery loads, and apparent attenuation rates across New Zealand to identify broad-scale patterns of headroom and over allocation.
Development of minimum information requirements for useful application of the sources and flows framework to a specific catchment.
Development of higher-level data requirements to increase the accuracy of the sources and flows framework when used in highly contentious or technically challenging settings.
Validation of the sources and flows framework across a range of different landscapes, farming systems, climates and climate change scenarios, receiving environments, and endusers including Māori.
Incorporation of the framework into the “interoperable models” and tools developed in the OL&W Challenge and other programmes.
Alignment of environmental performance indicators with considerations of product value chains that generate greater wealth for New Zealand.

Location

The focus of this programme is on developing an integrated framework based on existing biophysical knowledge therefore the science in the programme will synthesize data gathered from around the country.
Northland. We will be working with the Mauri whenua ora programme and associated iwi in the Northland region.
Southland. We will be working with the Suitability programme, Environment Southland and associated iwi in Southland to test our hypothesis number 4.
Waikato. We will be working with Landcorp on their farms in the upper Waikato catchment to test our hypothesis number 2.
The stakeholders involved in this programme are from Landcorp, DairyNZ, Beef+LambNZ, Rabo Bank, IrrigationNZ and Regional Councils (in particular Northland, Waikato and Southland). As yet none of the stakeholders have committed specific direct co-funding to this programme. However, all have agreed to provide their time as in-kind contribution. IrrigationNZ and DairyNZ have both got a number of existing research programs that will be able to supply relevant information to support this programme.

Integration

The Sources and Flows programme aligns strongly with four proposed programmes.

Suitability: alignment with this programme will be through shared case study sites. It is critical that the outputs from our programme at the impact sites in water can be integrated with the inputs for the Suitability programme. There will be significant information/progress sharing between the programmes to ensure they remain aligned. This is critical to test the shared hypothesis between the programmes that aims to link the sources from the land through to the resilience of the water body.
Targeted solutions: alignment with this programme will involve linking data from both this programme and the Suitability programme for a “headroom analysis” to identify the areas of NZ that are under the most pressure. These will be the areas that most urgently need new solutions for enhanced productivity under environmental constraints. Furthermore, this analysis will indicate which specific contaminants (N, P, Sediment or E. coli) are creating the most pressure and hence have the greatest need for alternative land-use or mitigation options.
Mauri whenua ora: Alignment with this programme is through shared case study sites in Northland. The Sources and Flows programme will provide the framework on contaminant sources and flows to support decision making in the Mauri whenua ora programme. The Mauri whenua ora program will test the framework and provide feedback on the usefulness of the framework and identify any additional information or outputs that may be required for use in their programme.
Nexus: The framework developed in this programme will need to be able to incorporate the relevant indicators that arise from the Matrix project.

Future OL&W programmes: Through the target contestable round, Sources and Flows will provide the underpinning data for additional modelling programmes enabling quantitative linkages from sources through land and water-scapes to receiving waters.

Research Methodology

The research in this programme has been separated into 7 workstreams. The first (1) is about integration of this programme within OL&W to cross-fertilise ideas and “join up the dots”. Workstreams 2 to 4 are the science workstreams that address (2) the overall framework for linking contaminants from sources to receiving environment, (3) potential of Indirect Measurement techniques to characterise dominant flow pathways in catchments and (4) Source-Delivery-Attenuation (SDA) analysis that can provide scientific evidence to support the outputs from the framework. The last 3 workstreams (5 to 7) are specific case-studies that will be conducted with (5) Landcorp Farms, (6) Māori land owners and enterprises in the Mauri whenua ora program and (7) the Suitability programme and Environment Southland.

1: Integration

Integration into wider OL&W programme will occur through joint meetings and on-going participation in the Matrix Programme. Active integration with the Suitability programme will occur via the joint case study in Southland, with collaborative meetings scheduled for April and May 2016. Our shared task will be to ensure that information on the sensitivity of the receiving environment (soils and water) can be linked into the Sources and Flows Framework so that these hierarchical frameworks align without gaps or unnecessary overlaps. Integration with the Targeted Solutions programme will occur through (at least) annual meetings to share progress and insight from the SDA analysis and associated understandings of “headroom”. We believe that understanding the headroom across the country will provide and understanding of where the water quality pressure is the highest and also which contaminants are creating the most pressure. This information will be important for the selection criteria used in the Targeted Solutions programme i.e. if the highest pressures are from P and Sediment contaminants in hill country then the Targeted Solutions will need to focus on developing new options for low P and Sediment Losses in these landscapes.

2: Framework

Working collaboratively with recognised experts across multiple disciplines this programme will review existing data, models and frameworks to co-develop a new interdisciplinary conceptual framework. This hierarchical framework will link sources of flow and multiple contaminants with transport pathways through the landscape, accounting for attenuation in unsaturated zones, interflow, groundwater, land:water interfaces and surface waters, and identifying where additional attenuation potential could be exploited or created. A hierarchical approach is needed to ensure that the information from all these steps can be accounted for between the point where a contaminant leaves an enterprise and when it has impact which may be in the catchment or in estuarine or marine environments at the mouth of the river. This approach is needed as current approaches typically consider all of the land in a region to contribute equally to water quality impacts. This will not be the case in some areas and may be limiting the potential productive returns from areas of land that are in fact having little impact on water quality outcomes.

The framework will operate at a range of scales, taking into consideration the critical factors of topography, climate, land use, soils and geology, and hydrology to encapsulate the main drivers of spatial and temporal variation in water and contaminant fluxes across catchments. Comprehensive catchment-scale models, such as SWAT28 can provide significant explanatory power in differentiating the effects of different land use scenarios29. However, they are expensive to set up because they require extensive high spatial resolution datasets and specialised science expertise to parameterise, calibrate and validate them. Additionally they don’t always come up with better estimates than simpler models30. For instance the SWAT model was comprehensively calibrated and tested in the Motueka Catchment achieving only moderate success31, 32. At the other end of the spectrum, Farm scale nutrient-budgeting models such as Overseer, have been designed to use typical farm production data as inputs and can be operated by trained end-users but only generate results on an annual time scale. Intermediate-complexity models such as CLUES which attempt to combine this farm-scale land-use information with landscape-scale data can provide adequate simulations of catchment responses for many purposes but also have significant limitations 32, 33. The challenge in developing this framework will be to find the appropriate balance (“sweet spot”) between explanatory power and availability and simplicity of required data inputs.

Where relevant we will incorporate aspects of existing frameworks such as the Farm Dairy Effluent Soils Risk Framework34, the Microbial Bypass Flow risk Maps 35, and the P Risk Assessment Framework for Stony Soils36. Thus this work will predominantly use knowledge and databases that already exist from a wide range of previous research programmes. However direct linkages of team members into related research will enable cutting-edge developments in thinking to be incorporated (e.g. from Pastoral21 Programme, led by AgResearch; Transfer Pathways Programme, led by Lincoln Agritech; and the Smart Aquifer Models Programme, led by GNS and collaborative work in Environment Southland’s Fluxes and Flows Programme). Any gaps in the Framework that cannot be filled with existing data will be highlighted to the OL&W Directorate to help identify opportunities to fill the gaps 37, 38. The novelty and stretch of this approach will be the complete linkage of contaminant flows from source to sea, which is a substantial challenge not attempted before. We will be working closely with stakeholders to keep our focus at the appropriate level of detail, and/or accuracy, needed to deliver to the stakeholders’ decision making needs. A conceptual framework will be developed and tested with stakeholders in the first 6 months of the programme. This will test that the users have ready access to the information required as inputs to the framework and that the outputs generated will produce the information required by stakeholders to make their decisions. Flexibility will be required to enable evaluation of the impacts of future climate change projections which are likely to substantially influence stream and river flows and variability, and contaminant export from different regions, landscapes and land-uses across New Zealand and around the world14, 26, 39-42.

3: Indirect methods

Indirect methods, using flow and water chemistry time series (“signatures”) measured at the catchment outlet will be reviewed to determine their utility for partitioning flow and contaminant pathways 1, 13, 43-45. These indirect methods have the advantage that they provide an integrative measure of the transfers and processes upstream and hence offer an alternative means to check catchment contaminant pathways to that proposed in the Framework. However, their applicability and utility is likely to be constrained by the low temporal resolution of most currently available monitoring data, and the limited availability of suitable supplementary information to aid interpretation (e.g. on soils and groundwater). For example, stable isotopes of nitrate can be used to determine the age of water and hence the dominant groundwater flow paths43. Or microbial source tracking tools can be used to determine if the faecal contaminant source is from human, farmed animal or wild animal sources which has a large effect on the associated health risk and mitigation approaches to address. Thus, as well as determining what can be gleaned from analysis of general monitoring data commonly run by Regional Councils and NIWA, we will identify where higher-resolution water chemistry and optical data is needed most. We will also explore the use of natural tracers as an alternative means to elucidate contaminant transport pathways. These indirect methods will be most useful for providing evidence on contaminant flow pathways to support stakeholder confidence in the transferability of the framework from one catchment to another.

4: National Catchment-scale Source-Delivery-Attenuation modelling-