As we walked along we were astonished to see a big branch sitting on the muddy bank, exposed from tip to tip.
Usually it looks like this. As it did yesterday.
Seeing we were at one of Penny's two favorite swimming spots, she headed on down to the water and swam happily for a stick, but we didn't like to see her slogging through the deep, soft mud, given that she had surgery on her cruciate sixteen months ago.
So moved on to the other spot, where the strangely low water has exposed rocks, not mud.
Melbourne Water has been working for months to rebuild the old weir at Dights Falls. Their site says:
The Waterways Alliance, on behalf of Melbourne Water, is completing works to replace the ageing Dights Falls Weir and build a new fishway on the Yarra River in Abbotsford.And...
The new weir will be similar in shape, location and height to the existing structure and continue an important role controlling water levels in the river.
A new fishway will allow fish to swim past the weir, benefiting 11 species of native migratory fish and unlocking vast reaches of the Yarra and its tributaries upstream.
A temporary diversion of the Yarra has been set up at Dights Falls to allow the construction of the new weir and fishway. The diversion will be in place until the new weir has been constructed and will cause river levels for up to 16 kilometres above the weir to temporarily drop below normal levels on occasions.
The drop in river level will cause sections of river bank, usually under water, to become exposed.
So that seems to be the answer to the mystery.