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Climate impacts on water supply

Objectives: Severn Trent Water used UKCP09's joint probability plots to help understand the in-combination effects of climate change on water service activities. In the absence of simple thresholds for the individual variables, past events have been used to understand the implications of the climate change scenarios for future water supply.

UKCP09 products used: User Interface.

How were UKCP09 products used?

  1. 1995, 2003 and 2006 were identified as examples of recent years when high summer temperatures and low rainfall led to extreme peak demand for water.
  1. The Environment Agency provided long-term average precipitation data covering the 1961-1990 period in the Severn Trent region, and also weekly rainfall updates from 1995 onwards. Using this data, anomalies for the identified example years were calculated.
  1. The Met Office Hadley Centre provided central England average temperature data covering the 1961-1990 period. Using this data, anomalies for the identified example years were calculated.
  1. These joint anomalies were used to plot a point on to temperature and precipitation joint probability plots of the 2050s and 2080s to give an indication of where a past event might compare to a potential future.

Difficulties & limitations

The plots can only be downloaded in a picture form (.jpeg or .bmp file) so plotting anomalies on the joint probability plots could only be done by eye using picture-editing software. The picture form of the plots also means it is not possible to plot more extreme conditions experienced in the region, for example the 1995 anomalies due to fixed axes.

The Severn Trent Water region cuts across two regions of UKCP09 (West and East Midlands), making climate change impact analysis complicated. For example, climate data for whole region would have to be plotted on both the West Midlands joint probability plot and the East Midlands joint probability plot.

Lessons learned

  • Downloading of data/graphs and maps can be slow.
  • Company data could be easily plotted using MS Office application, which made it useful for setting context with historical data.
  • Careful presentation is needed to convey probabilistic information accurately but in a manner which users can understand.

How will the results be communicated to the target audience?

This analysis has been done as part of the Climate Change Risk Adaptation work. The report includes analysis of historic events and use of joint probability plots to understand what the future may hold i.e. it contextualises the data for current operations against potential future conditions.

Find out more 

  • Contact details: Ismail Mulla, Marcus O'Kane, Sarah Smith, Justin Garratt, Severn Trent Water.