You are in > Home > SAC Learning > Geography For Schools > Physical Geography > Rivers > The River Tay: A case study

The River Tay

A Case Study

The River Tay is the longest river in Scotland and the largest volume river in Great Britain. It has a length of 193 kilometres - stretching from the slopes of Ben Lui to the Firth of Tay near Dundee and has a catchment area in excess of 5,000 square kilometres.


The River Dochart, the furthest headwaters, is on the slopes of Ben Lui (1130 metres), on the borders of Perthshire and Argyllshire, which flow northwards to form the Fillan Water.

This moderate-sized stream runs eastwards to feed Loch Dochart, out of the loch flows the River Dochart which runs through Loch Lubhair, and then continues eastward to enter Loch Tay at Killin.

Issuing from the eastern end of Loch Tay at Kenmore, the River Tay flows east and south before emptying into Firth of Tay. "Firth" is the Scots word to denote Coastal waters, often an estuary.

The river is almost entirely rural upstream of Perth, and at Perth, the Tay becomes tidal but it is still more than 20 miles before the Tay reaches the sea in a typical example of a large estuary in Scotland.

The dominant land covers of the River Tay are moorland (about 45%), rough grass (about 19%) and forest/wood (about 18%).

Flooding

The Tay has always been susceptible to floods, though the steep topography limits the extent of floodplain in many areas.

The River Tay is nowadays well regulated through a number of reservoirs built for hydroelectric power (HEP) supply purposes. However, flooding still occurs during periods of extreme weather conditions.

The city of Perth suffered severe flooding in 1990 and 1993. Since then approximately £26 million has been spent on flood defences in the city to protect the main urban area from extreme floods (both fluvial and tidal). The Highest ever flood in Perth occurred in 1814 when the river rose 7m above its usual level.

Measuring the Volume of Water

The discharge of a river is measured in units known as cumecs (cubic metres per second). It is calculated by measuring the cross-section of the river channel and multiplying it by the speed of the flow of the water e.g. a 10 metre wide river with a depth of 5 metres with water flowing at 3 metres a second would produce 10x5x3 cumecs (150 cumecs)

In terms of volume of water The River Tay has a typical flow in excess of 100 cumecs near Kenmore with an average daily flow of approximately 175 cumecs at Perth.

Special Area of Conservation

Approximately 10,000 ha of the River Tay is designated a special area of conservation (SAC).

The primary reason for this designation is because the River Tay supports a high quality Atlantic salmon (Salmo salar) population. There is considerable ecological variety in the Tay catchment, resulting in the Tay supporting the full range of salmon life-history types found in Scotland.

Although not a primary reason for selection as a SAC, the Tay also supports various species of lamprey as well as otter populations.

Useful Websites

 

Author:
Kyrsten Black