Thanks, everyone for your helpful contributions. It looks very much as if it was the River Withert. I wonder if it got the name from drying up in dry weather - 'withering' in other words.
I find it sad that streams like this disappear and get forgotten about. I suppose when we are all dead and gone and mankind has passed and gone it will eventually reassert itself.
One of the links took me to a mention of the Rubicon. This used to run below Borough road, and in heavy rain was prone to flood. In the 1950s, I think, it was decided to do something about it and at about the junction of Borough Road and Clarence road, there is an underground weir. When the flow gets too high, it overflows the weir and goes into a tunnel leading back up towards Everest Road by the Tranmere Rovers stadium.
It then takes a sharp left and dives through a deep tunnel running 30 metres below Everest road, passes the Sportsman Pub
and goes below the park until it reaches Albany road at about Inglemere Road. It then runs below Albany road and St Pauls road and comes out into the river underneath the jetty in the oil terminal. The portal can be seen if you are in a small boat on the river.
At least it used to. I suspect it has now been intercepted at the Junction of St Paul's Road and the Rock Ferry bypass and finds its way to the underground pumping station at the bottom of the Dell where it is pumped to Bromborough treatment plant.
We rarely think about the infrastructure that removes our waste and rainwater. Who, sitting in the Sportsman Pub
of a wet evening is aware that deep below him is a torrential river flowing through a six-foot diameter tunnel on its way to the sea.