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A brief history of hydrometric monitoring in Scotland

SEPA monitors water levels and river flows throughout Scotland. Although electronic records didn't begin until the late 1970s, paper records go back to the start of the 20th century.

Captain WN McClean initiated the first systematic approach to river gauging in 1913 on the River Garry at Invergarry. His objective was to investigate the potential for hydro-electric power through an assessment of the yield of the Garry catchment. Prior to 1913, ad hoc gauging and level monitoring had been carried out for specific purposes such as water supply. Following McClean's work on the Garry, other stations were installed for the purpose of hydro schemes.

The Department of Agriculture for Scotland (Department of Agriculture and Fisheries for Scotland (DAFS) from 1959) installed stations on major rivers from 1947 and took the first steps towards a national network. These sites were principally installed to assess yield.

The Inland Surface Water Survey Committee (formed in 1950) published records for 38 stations, six of which were in Scotland. These six were privately operated by McClean's River-Flow Records.

The formation of the River Purification Boards (RPBs) from 1951 onwards led to a sudden expansion in the network as stations were installed to support their pollution control powers.

In 1954 the Central Advisory Water Committee published a year book in which 22 of the 81 stations were in Scotland. This increased to 30 in 1959 (although there were an additional 47 operational gauges).

Network development was not uniform across Scotland at this time. The North West Highlands and the islands were still not covered by a RPB and the southern RPBs such as the Lothian, Clyde and Tweed tended to be more active than those in the North. However the North of Scotland Hydro-Electric Board was also active and had constructed stations on the rivers Beauly (Erchless), Ness (Ness Castle Farm), Allt Bhlaraidh and Lyon (Moar).

An Inter-Departmental Committee comprising the Department of Health, DAFS, Scottish Home Department and North of Scotland Hydro Electric Board was formed in 1959 to report on the arrangements for river surveying and gauging and to make recommendations on the need for co-coordinating and extending the work and its publication. The RPBs and Scottish Council (Development and Industry) were also involved in discussions. The committee proposed a centrally managed network of 77 primary and 140 secondary stations.

The Scottish Development Department (SDD) was formed in 1962 and allowed for stations to be set up for the purpose of monitoring pollution and yield. By 1969 there were 162 stations with the basic network being the dominant element. The SDD held responsibility for stations in the North and provided grant aid for stations to the RPBs.

The reorganisation of the RPBs in 1973, and the Control of Pollution Act 1974, led to further expansion of the network with 224 stations in operation in 1979. During 1978 and 1979 the RPBs took on the remaining SDD sites so completing the move towards a single gauging authority in Scotland. One of the main drivers for continuing expansion of the hydrometric network in the 1980s was the development of a number of new flood warning schemes in response to the transfer of discretionary powers for these from Local Authorities to the RPBs in 1982.

SEPA was formed in 1996 and inherited 330 sites from the RPBs. Since then the network has expanded to help deliver SEPA's duties under a number of European Directives. For example, the introduction of the Water Framework Directive (2000) resulted in a new holistic approach to water management, including the licensing of water abstraction, the control of diffuse pollution and the consideration of flow regimes in environmental standards. Flow modelling has required a better understanding of flow regimes from lochs, small catchments and from areas that previously had a sparse coverage of stations such as the Highlands and Islands. The expansion of SEPA's flood management and climate change remit has also been a dominant driver in the development of new stations. By the beginning of 2010, SEPA was operating 443 gauging stations. A review of the network in 2010 which assessed utility and resources led to the mothballing of 50 lower value stations. Financial pressure in the public sector has focused attention on efficiency and although new sites were installed in 2010/2011, this has been counterbalanced by renewed network evaluation and further mothball proposals with a projected reduction of stations to 391 by the end of 2011.

For an earlier history of hydrometry in Scotland, readers are referred to Black, A.R. and Cranston, M.D., 1995. "River flow gauging station data usage and network evolution in Scotland" In: British Hydrological Society 5th National Hydrology Symposium, Edinburgh, 1995.