Lakes

[RainfallNZ]

There are several lake assessment points associated with oxbow lakes on the Mataura.
It seems likely that these lakes might be hyperheic so there water is coming from the Mataura, not the small sub catchments as provided in the REC. This means the water quality estimates from CASM are likely to be incorrect. Lake ID's include:
43846 44033 43823 43635

Note that 43829 is a special case. The REC appears to have this wrongly connected to Tiriroa Stream. This is the nzsegment provided in the lake assessment point file. Revieing the NZtopo map, this lake should drain directly to the Mataura.

[RainfallNZ]

Ton has requested that I review all the lakes and document the details of any that I decide need not be considered.

[RainfallNZ]

In some parallel analysis, Ton removes these lakes:
lake LID == 54742 is actually the Waituna Lagoon. lake LID == 25245 is actually the Waimatuku estuary lake LID == 43639 is actually the Lake Brunton

[RainfallNZ]

A draft review document has been prepared and is being reviewed by Ton. 14 sites were considered unlikely to result in reasonable contaminant concentrations. Of them 1 (Lake ID 53550) could be resolved through changing it's associated REC reach. The others were assessed as likely to be hydrologically connected (through groundwater paths) with a river reach that is different to the REC reach provided in the lake file.

[RainfallNZ]

Environment Southland reviewed the lake issues. Emails between Keryn Roberts and Ton (dates 10th and 11th August 2020) with subject "RE: Lake Inflow loads" indicate that most of the lakes can be removed from the CASM model.