The River Thames and it's variety of Locks.
The River Thames is navigable from Lechlade which is on the edge of the Cotswold Hills in Gloucestershire - the first of the 45 locks along the route of the Thames is St John's Lock at Lechlade - this lock is 110 feet long and just under 15 feet wide. Generally this is the average size for most of the locks as far down as Osney Lock
from where they tend to be somewhat larger, Curiously several of the locks, for instance at Mapledurham and Hambleden, are extra large within this sequence as they are around 200 feet long. These larger Thames locks were re-constructed after WW2 and according to one lock keeper they were built somewhat larger just to create work for local people.
The average length and width of the locks does increase as the River Thames gets nearer to London with Teddington Barge Lock being an impressive 650 feet long and nearly 25 feet across.
eastern end of the River Thames (i.e. as the river approaches London) the final lock* which has to be navigated is located at Teddington where there are in fact three different capacity locks to chose to use obviously depending on the size of the boat.
There is however a lock just a little further down at *Richmond but using this is optional as boats can go simply go on through Richmond's barrage two hours either side of high tide.
Todays locks are the replacement for the original single gated "flash" locks - i.e. the
water is contained in a chamber or "pound" and held there by two sets of lock gates. The locks on The Thames between St. Johns Lock at Lechlade and Kings Lock (a little to the north of Oxford) are still manually operated but thereafter the locks are hydraulically operated. Many of the River Thames Locks are manned during the day and have lock-keeper's cottages situated beside the locks - they are generally surrounded by
beautifully kept gardens and flower-beds - for instance at Grafton Lock and Kings Lock (near Oxford) and often there are bench seats dotted around.
Sandford-on-Thames has two particular features - it boasts the lock with the greatest drop on the River Thames - the lock is 174 feet long and 21 feet 9 inches wide with a fall of 8 feet 10 inches. Sandford Lasher is the quite appropriate name for Sandford Lock's weir and is situated a little way from the lock itself - the water at Sandford Lasher is extremely dangerous and the pools often have whirlpools.
Quite understandably access onto Sandford Lasher weir is not allowed and the immediate area is fenced with iron railings.
Using and Operating the Locks on the River Thames.
Although many of the locks on the river are manned and therefore the lock-keeper will do all or most of the opening and closing of sluices and gates for you certainly during lunch times you may find the lock is unmanned - usually indicated by a "Self Service" sign at the lock. In case of the latter then to proceed first of all
ensure that the gates and sluices are fully closed - i.e. the red sluice indicators are in the lowest position.Filling the Lock.
Open the sluices on the the upper lock gates by winding the control wheel until the red indicators and white indicators are at the same level. When the lock is half full then you can fully open the sluices i.e. wind the wheel to
get the red indicator bar fully raised.To Empty the Lock.
Open the sluices very slowly on the lower lock gates by winding the control wheel until the red indicators are fully raised - "slowly" is important to avoid turbulence in the water.
Once the water levels are even open the lock-gates by pushing the gate beams.
Once through the lock the lock-gates
and sluices should be left fully closed
unless another boat is waiting to use the lock - or of course if there is a sign from the lock-keeper requesting you do otherwise.