St Patrick's Stream or Patrick Stream is a backwater of the River Thames

River Thames

The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

 in England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, which flows into the River Loddon

River Loddon

The River Loddon is a river in the English counties of Berkshire and Hampshire. It is a tributary of the River Thames, rising within the urban area of Basingstoke and flowing to meet the Thames near the village of Wargrave...

 near Wargrave

Wargrave

Wargrave is a large village and civil parish in the English county of Berkshire, which encloses the confluence of the River Loddon and the River Thames. It is in the Borough of Wokingham...

, Berkshire

Berkshire

Berkshire is a historic county in the South of England. It is also often referred to as the Royal County of Berkshire because of the presence of the royal residence of Windsor Castle in the county; this usage, which dates to the 19th century at least, was recognised by the Queen in 1957, and...

. It leaves the Thames on the reach above Shiplake Lock

Shiplake Lock

Shiplake Lock is a lock and weir situated on the River Thames in England near the village of Shiplake, Oxfordshire. It is just above the points where the River Loddon joins the Thames and Shiplake Railway Bridge crosses the river...

 near Buck Ait

Buck Ait

Buck Ait is an island in the River Thames in Oxfordshire, England. It is on the reach above Shiplake Lock near Sonning.The island is uninhabited and tree covered but sits opposite houses with extensive river frontages...

, downstream of Sonning

Sonning

Sonning, occasionally called Sonning-on-Thames is a village and civil parish in the Borough of Wokingham in the English county of Berkshire, a few miles east of Reading. The village is situated on the River Thames and was described by Jerome K...

.

It is believed that the stream was originally a branch of the River Loddon that flowed into the Thames. However when Shiplake Lock was built, the water level was raised to such an extent that it became an outfall. Evidence to support this includes a 13th century charter

Charter

A charter is the grant of authority or rights, stating that the granter formally recognizes the prerogative of the recipient to exercise the rights specified...

stating, "Where the Lodone falls into the Thames under the park of Suninges", the contention that the stream is private and not public Thames water and the shape of the junction point which suggests a tributary rather than an outflow.