Friday 12 August 2016

Summer low flows



The end of July and the first half of August have been mostly dry, and you can see the stage following a decreasing trend interrupted by a couple of rainfall events. Conditions are hot with highs in the 30s Celsius, and so ET is high during the daytime and this shows up on the stage hydrograph as a series of dips.



Today I measured the discharge at a stage of 30cm, and then installed a new stage recorder (HOBO) attaching it to the steel pipe of the staff gauge within a housing of PVC pipe. The pressure transducer I've been using since 2000 has started to become rather erratic and I suspect it is no longer venting properly with changes in atmospheric pressure. It shows drift from the observed staff gauge reading of up to 25mm after a couple of weeks. Today it was 10mm too low before I reset the offset.