Talk on local climate – Gareth Varney

Gareth works as the Hydrometry and Telemetry Programme Manager for the Environment Agency in the Wessex region. His team monitors rainfall, soil moisture, groundwater and sea levels and river flows and levels, using specialist equipment at over 500 sites.

Weather monitoring

Their monitoring assists in the management of rivers and groundwater, including abstraction, discharge, availability and quality, including pollution. In recent years, about 90% of their work has been devoted to flood risk management.

The agency has many flood managements assets, including pumping stations, gates and sluices, spillways, and alleviation and attenuation schemes. They can also deploy temporary defences and pumps and undertake emergency works.

Somerset pumping

Increasingly, their data and webcams are being made available online – see:

Water flows and levels can be influenced by air and water temperatures, as shown by Simon’s data and other records. They may also change with variations in the Jet stream (strong high winds which move weather systems around the Earth) and Gulf stream (a strong ocean current which brings warmth to the UK). In relation to climate change, a key factor is that warm air holds more moisture, leading to more rainfall.

Jet stream

Future projections for the UK due to climate change are greater rainfall, wider variability and greater rainfall intensity.

Consistent above average intensity and frequency of rain led to the Somerset floods in 2013/14, when there was very high rainfall in October and then again in December, January and February.

However, annual rainfall recorded at Barrow Gurney from 1910-2016, shows there has been considerable variation in rainfall from year to year and no clear upward trend. It can be noticed that some of the wettest and driest periods have occurred since 2000, but some also occurred going back to the early 1900s.

The table below shows the long-term average rainfall for 30-year periods by month at Maundown. Since 1961-90, there are sizeable increases for July, October, November and December, and small decreases for February and August and an overall reduction for September.

Maundown rainfall

River flow records for the River Tone at Bishops Hull appears to show a clear upward trend from 1968 to 2016.

Data for England and the South West shows a change from drought conditions, with below average rainfall from 2010 to April 2012, changing to flood, with above average from April to September 2012. This lead to a sustained increase in the base flow, along with many high peaks, for the River Tone at Bishops Hull.

Somerset floods

The evidence for increases in temperature and rainfall is strong, but increases in flooding and peak river flows are only partially attributable to climate change.

Other factors are:

  • Increased run off and reduced flood attenuation (reduction) due to:
    • Increased urbanisation (gives more run off and reduced floodplain storage).
    • Changes in catchment land use (related to crop types and amount of woodland).
    • Improved drainage.
  • Reduced surface water and fluvial (river) maintenance.
  • The historic infrastructure.
  • Social change, including in water use, abuse of wastewater, and increased awareness of flooding due to news reporting and social media.

Possibly, rising sea levels should be an even bigger concern, as tidal defence failure could be more critical. 1000’s miles of tidal defences protect 100,000’s of homes and historic tidal defences for storm surges now need adjustment for climate change. Incoming tide lockage also has potential to restrict river outflow.

Flooded field

See slides presented by Gareth Varney.

See notes on talk by Simon Ratsey.

Return to home page post on local climate change talks.

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