EFSAP - Piako Catchment Waikato

The EFSAP was tested by the Waikato Regional Council (WRC) as a means to better explore options and changes being proposed in the Waikato Regional Plan to address new requirement in the National Policy Statement for Freshwater Management (NPS) of 2011.

This report evaluates the EFSAP using the Piako River catchment area as a case study. The EFSAP platform was used because of the need both address changes on policy while also having necessary regard to both instream (e.g. Ecosystem health and natural character) and out of stream (e.g. Drinking water supply) values when considering these changes to water management.

EFSAP is a tool designed to enable planners and water allocation decision-makers to simulate and compare spatially explicit water management scenarios at catchment, regional and national scales. The model is firstly based on the spatial framework; the River Environment Classification (REC; Snelder & Biggs 2002) which combines segments of the river with several attributes including topography, geology and climate to classify an overall catchment. This spatial data is combined with hydrologic characteristics, which for this case study included; 1 in 5 year mean annual 7-day low flow, mean flow, the shape of the flow duration curve and further generalised habitat vs. flow relationships.

From these key data inputs analysis can be carried out using four key variables; flow changes, total allocation, minimum flow, reliability of supply and habitat change. For any given scenario or simulation two of these variables may be held constant whilst the other two will be calculated throughout the catchment area.

 

 

 EFSAP pri allocation reliability

Predicted reliability of supply for the Primary Allocation if the Plan rules are applied uniformly (Scenario 1).

 

Within the Piako catchment case study it was possible to compare modelled results in scenarios to reality. This was an important feature for this study as future planning in the area was to be considered. The comparisons of scenarios in this study indicated that there were significant levels of over allocation of resources within the catchment under current guidelines; this highlighted the fact that there may be significant implications for WRC with respect to fulfilling the requirements of the 2011 NPS. It was noted that the degree of over allocation was a variable that changed throughout the catchment; ranging in this study from 0% to 598% over allocation, this turns out to be a useful part of EFSAP given that it is likely that the scale of outputs provided by EFSAP may be more representative of the status of a catchment than assessment at individual points in the catchment.

 

EFSAP shortfin change

Predicted change in shortfin eel habitat availability relative to mean annual low flow when the Primary and Secondary Allocations are fully allocated.

 

It was concluded that EFSAP methodology had been demonstrated to offer an approach that allows water managers a means to evaluate the consequences of changes to regional water management strategies. As such this platform has proven a possible means to model proposed solutions that respond to national changes in policy as well as, quite importantly, characterising the consequences of existing allocations, which as shown here can be already below current allocation standards.

Associated Models

Environmental Flows Strategic Allocation Platform (EFSAP)

EFSAP was developed by NIWA as a water allocation decision support tool.

References

Paul Franklin, Jani Diettrich and Doug Booker (2014): Evaluation of a tool for investigating water allocation scenarios: A test case for the Piako catchment. NIWA Report Prepared for Waikato Regional Council. Waikato Regional Council TR2014/52

Snelder, T.; Biggs, B.J.F. (2002). Multi-scale river environment classification for water resources management. Journal of the American Water Resources Association 38(5): 1225-1239.
http://dx.doi.org/10.1111/j.1752-1688.2002.tb04344.x