instruments tend to be expensive, require more effort with installation, potentially more exposed to flood events, and they still need referenced against “gauged” flow values. The installation of a simple weir at some locations will improve level measurement sensitivity and stability of the location over time. Suggest this will not be feasible / realistic for the mainstream locations i.e. wider more substantial channel. From the rating development undertaken by WSP (memo to OGL dated May 2021) the low stage rating for T-StreamWest and T-Stream East locations appeared reasonable stable for 2-years of data collection. Data quality would improve with vented transducers. Also, instrument upgrades would be required if the sites are to be telemetered. Near-time telemetry of the existing and proposed monitoring sites is possible, and clearly more difficult for some locations. The operational requirement for telemetry during the baseline data collection phase was not explicit in the GHD memo. There will be merit to at least initially telemeter one location to define the costs and operational limitations of telemetry in this catchment (especially if telemetered flow data will in the future be an operational requirement). The raingauge if not reinstated, should be. The weather station, depending on parameters measured (or to be measured), may (will) provide sufficient information to determine potential evaporation rates. Measuring evaporation may assist with the development of the GHD catchment model. Flow measurement is in effect the measurement of nett precipitation (including lag effects, gains and losses). Operationally, flow trigger thresholds may best be assessed from measured flow (and not rainfall modelled). Low flow thresholds will not be “event” based.
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