Assessment locations

CASM requires details of where contaminant loads need to be calculated.
Selection of the assessment locations needs to consider:

• Representativeness of upstream land use types,
• problem areas,
• areas where policy and rule changes are likely to have an impact,
• proximity to each other,
• model complexity.

A limit of 200 sites was set to ensures the models ability is not over stated, and to keep the CASM models manageable.
Initially site selection was derived as follows:

• All water quality measurement sites were included (57 so far).
• The "priority" estuaries were included (10 of them).
• The lakes that have water quality monitoring were included (5 of them).
• Subjectively (by Tim Kerr) chosen sites of tributary junctions (10) and physiography changes (2) and representative pristine (1).
• Subjectively (by Tim Kerr) chosen river outlet points.
• Objective selection of reaches at the base of catchments that are greater than strahler order 5 were, but with any sites removed that were in lakes, terminal reaches, or were already represented.

Environment Southland technical staff were requested to review the sites and submit requests for additions and deletions. To help them, they were provided with a map of the locations, histograms of how well the points represented the distribution of exotic grassland coverage, catchment areas, and water management classes, and an explanation of what the locations were needed for, and how the initial sites had been selected. A video meeting was then held to discuss the points.