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Climate impacts on pollution levels in watercourses in Birmingham

Objectives: The Environment Agency and Acclimatise used UKCP09 to examine how climate change could affect pollution in two urban watercourses in Birmingham. The watercourses are polluted by sewage and diffuse urban pollution and drain into a lake used for recreation. Local groups and Birmingham City Council wish to know if climate change will cause an increase or decrease in pollution.

UKCP09 products used: Maps and Key Findings; User Interface; Threshold Detector.

How were UKCP09 products used?

  1. Records from the Environment Agency's National Incident Recording System (NIRS) were used to identify weather-related pollution incidents. Local rainfall data was then used to look at the conditions on the day of the incident. The rainfall for the previous 30-45 days was also examined as dry spells followed by intense rainfall are thought to lead to the greatest pollution.
  1. Out of 10 incidents in 2008-2009, two were linked to high rainfall, with daily rainfall totals of 14 mm and 29 mm. Both occurred in summer following a week without rainfall. To investigate how this may change in the future, UKCP09 was used to further examine dry weather in summer followed by high rainfall.
  1. UKCP09 key findings were used to identify change in summer mean precipitation in the West Midlands for the 2020s and 2050s and CDF graphs were used to identify changes in summer precipitation on the wettest day, focusing on Birmingham in the 2050s. 
  1. To establish how the frequency of wet days may change, the threshold detector tool was used. Changes in the frequencies of simple (single) events were investigated which firstly looked at 14 consecutive dry days and secondly looked at rainfall greater than 24 mm for 1 day.  A complex (combination of sequences of) event was then run which examined both of the simple events together.

Difficulties & limitations

Ultimately this study is limited by the lack of understanding of weather conditions that generate pollution incidents. 

Lessons learned

This approach has only investigated a single scenario. Different results could have been derived by looking at 5 quite dry days followed by 20 mm of rain. However, it would become very time-consuming to generate multiple scenarios this way. Weather Generator outputs could be evaluated directly but this would require computer-programming skills and is probably beyond the average user. Care needs to be taken with extreme events, which may be stretching the capacity of the Weather Generator.

The analysis undertaken is not a sufficient basis for a major investment but it does provide a useful and relatively quick indication of how pollution-causing conditions may change in the future. 

How will the results be communicated to the target audience?

This case study forms part of a wider project that makes information on using UKCP09 available to an internal Environment Agency audience.

Find out more

  • Contact details: Bob Khosa, Acclimatise and Glenn Watts, Environment Agency