How is flow estimated?

EA SHIPLAKE Downstream graph
EA SHIPLAKE Upstream graph

from Environment Agency Guide 2012-2013

Right bank, length: 133'4", width: 18'3"
1404: -

  Elizabeth, Prioress of Goring has a lock in the water of Thames [below] Shiplake, of such height and width that all men with shouts and barges and kidels can pass thereby without danger as of old time.

1585:  Bishop – Shiplake Lock “kept by Rd. Cotterell and belongs to the Crown”.
1746: Griffiths – “Cottrell’s Lock”.
1773:  Shiplake Pound Lock opened (built in fir).
1775:  Bowen’s Map – “Cotterill’s”.
1787:  Lock rebuilt in oak.
1790:  Ireland –

Cotterell’s Mill and Lock – a very picturesque scene, highly deserving observation.

1794: Report of a survey of the river Thames between Reading and Isleworth ... John Rennie (the Elder)

... I found the old stanch in very bad repair, and if something is not speedily done, it is probable it may be carried away by the floods.
At Cotterel's Lock the water was five inches under the gauge mark; but there had been a flash let down from Sunning during the time these Observations were making, which will create a small difference in the soundings, but not sufficient to cause any material difference.
The water was five feet nine inches deep on the upper sill of the lock, and this depth seems necessary for the mills, of which one is a paper and the other a corn mill; and I am informed they often work down the head two feet under the gauge mark.
While I was taking my measurements at the lock, a Newbury barge brought down a second flash with her, which raised the water on the lower sill of the lock from three feet nine inches to four feet eleven, and from being under, to two inches above the gauge mark at Marshes lock: with this flash the soundings were taken downwards.
The tail cut from Cotterel's Mills coming into the navigation some distance below the lock, on the towing path side, renders the towing very inconvenicnt. A towing path bridge should be made across the mill head, and another across the tail, by which means the barges would be hauled by the horses into and out of the lock, whereas at present they are pushed by poles.
There are many shoals [below the lock] between the ayt near Bowney Flats and Cotterel's Lock, which, if ballasted away, would lessen the water on the lower sill of the lock, and thereby prevent the barges from getting into it. To remedy this, the lower sill should be sunk eighteen inches, and the shoals ballasted, and in order to keep them to their depth, the channel should be contracted on the Berks side,- which in these districts might easily be done by planting willows on the ayts, to collect silt from the floods.
[Above Shiplalke Lock] From Lynche's ayt to Cottrell's lock there is a sufficient depth of water.

1874:  Shiplake Lock entirely rebuilt.

1881: George Leslie, "Our River" -

To return to Shiplake Mill and Lock. The mill is a fine specimen of a Thames mill, having plenty of nice woodwork about it;  the lock is at present kept by an old man-of-war’s man, who has erected a flagstaff in his garden, and hoists the colours on it in orthodox fashion.  Little camping parties are here generally found;  the view of the mill from the weir water behind the lock is a good one, and the whole of this water with its eyots will repay inspection.

1885:  weir rebuilt.  Fred Thacker says –

The old weir was higher upstream than the present one;  extending diagonally across from the danger post to the little promontory above on the LEFT bank, where the tall trees stand and an iron capped pile.

1889: Lock Island purchased by the Corporation of London for pleasure camping.
1889: A S Krausse, A Pictorial History of the Thames -

Shiplake Lock boasts of a flag-staff, from which the keeper, Constantine by name, a very popular ex-navy man, flies his flag on suitable occasions. The Lock Island, and the banks of the weir pool alongside, provide exceptionally convenient spots for camping, a fact which is taken advantage of by innumerable parties, who may be seen during the summer months making the scene animated with their tents. Intending campers should communicate wth Constantine at the Lock.

1890: Shiplake from weir bridge, Francis Frith -

1890: Shiplake from weir bridge, Francis Frith
1890: Shiplake from weir bridge, Francis Frith

[ You can see the Corporation of London camping site established the previous year. ]
1890: Below Shiplake Lock, Francis Frith -

Shiplake Lock Camping
London Corporation Camp site on Shiplake Lock Island

From Wargrave History Society:

The island camp site consists of 18 plots. It was originally privately owned until 1891, and camping was already a regular activity there by that time, using ridge tents, and lit by oil lamps - as some still are.
The land was offered for auction in 1891, for 'potential hotel development', but a benefactor named Crawford paid £836/12/8d for the land, ensured it had a restrictive covenant to preserve the camping rights, and then sold it at cost to the City of London.
Due to the distance involved, the City found some difficulty in administering the island, and so in 1914 granted a £1 per year perpetual lease for 2000 years, with the restrictive covenant in place, to the Thames Conservancy.
The camps were then being run by the lock keepers, who hired out skiffs and punts to islanders.
In the early 1900s the conservancy allowed huts to built near the tents - as it was thought safer for cooking - but they were not to be used for sleeping.
At that time, ladies were not allowed to sleep on the island, but had to retire to wooden huts on the Shiplake side.
The Thames Conservancy refused - as have the National Rivers Authority and Environment Agency since - to give more than a 1 year at a time lease to the plotholders.
Despite that, the community has remained remarkably static - usually plots pass-ing from father to son.
The families come from a wide area - the West Country, Liverpool, Leeds etc.
Since 1945, there have been 4 marriages between island families.

1890:  Below Shiplake Lock, Francis Frith
1890:  Below Shiplake Lock, Francis Frith

1890: Below Shiplake Mill and Lock, Francis Frith

1890:  Below Shiplake Mill and Lock, Francis Frith
1890:  Below Shiplake Mill and Lock, Francis Frith

Lantern slide 1883-1906, W.C.Hughes, research by Dr Wilson, courtesy of Pat Furley

Shiplake Mill, lantern slide 1883-1906, W.C.Hughes, research by Dr Wilson, courtesy of Pat Furley

1895: Shiplake Lock and Mill, Henry Taunt -

Shiplake Lock and Mill, Henry Taunt, 1895
Shiplake Lock and Mill, Henry Taunt, 1895
© Oxfordshire County Council Photographic Archive; HT08318

1907:  Shiplake Mill demolished –

being in a ruinous condition and no tenant obtainable.

1955:  Shiplake Lock, Francis Frith -

1955:  Shiplake Lock, Francis Frith
1955:  Shiplake Lock, Francis Frith

1960: Shiplake Lock is the first Thames lock to have a Hydraulic system installed.

1999: Above Shiplake Lock -

Above Shiplake Lock
Above Shiplake Lock.

2011: SHIPLAKE Lock named the best-kept lock on the Thames -

In the Environment Agency’s Thames Waterways Awards ...
Lock-keeper Geoff Horsnell, who has run the lock for the past 20 years, said he was delighted.
“For Shiplake to be voted the best kept lock by users of the river is a great honour,” he said.
“I really am very flattered. I look after all the plants and flowers myself but, being a keen gardener, it gives me great satisfaction and it really is a labour of love. The flowers come out in the summer and go back in the winter every year and it is very satisfying to know that they are enjoyed by the boating fraternity.”