First discharge measurement

Today I am joined by some new faces in the field - for three of our members it is the first time to make a discharge measurement. Our measurement is very important in establishing the new stage-rating curve after the channel degradation during summer floods. As shown in the stage hydrograph below, the recent 11 days have been mostly low flows with minor rainfall events.

Late summer low flows

A series of storm events during late August led to multiple peaks in the stage hydrograph shown below, the highest peak reaching almost 1.4 metres. September is normally a season of late summer low flows when the annual minimum daily flows are often recorded. Aggradation and accumulation of sediment in the gauging reach occurred in early summer floods, but these recent floods have led to net removal of sediment and deepening of the channel in the gauging reach. Changes in the stage-rating curve need to be closely monitored to maintain accuracy in discharge estimation.