Developing the new CEH-Gridded Estimates of Areal Rainfall dataset

Watch a presentation by Dr Maliko Tanguy of the Centre for Ecology & Hydrology about the new CEH-Gridded Estimates of Areal Rainfall dataset (GEAR). The talk explores the motivations behind development of the dataset, including user and data management needs, explains how the data was derived, and provides some example uses. CEH-GEAR provides 1km gridded estimates of daily and monthly rainfall totals for Great Britain and Northern Ireland from 1890 to 2012, with yearly updates. Precipitation totals from the UK raingauge network are used.




The CEH-GEAR dataset will be available via the CEH Information Gateway by the end of the year.

Additional information

The presentation above was made to an internal CEH audience in September 2014.

CEH Information Gateway

View slides from the presentation made at the British Hydrology Society 2014 National Symposium

Potential influences on the United Kingdom's floods of winter 2013/14

Last winter severe flooding affected large parts of the UK. In a recent paper published in Nature Climate Change, scientists at the Centre for Ecology & Hydrology, working with colleagues from the Met Office and a number of universities, looked at the possible drivers behind the floods.

Dr Chris Huntingford, the lead author of the paper, explains:

In this paper, along with my co-authors, we have tried to provide a summary document that collates and discusses all possible drivers behind the major flood events that affected the UK last winter. It has three themes.

First, a very brief overview of the large-scale meteorological events leading up to the storms is presented. None of the individual rainfall events was unprecedented, but the weather patterns behind them persisted for three months causing a near-continuous succession of Westerly storms. This had the cumulative effect that for much of the Southern UK, the total winter rainfall was record-breaking. Preliminary analysis suggests that particularly warm ocean conditions and heavy rainfall in and around Indonesia triggered wind patterns across the Pacific that travelled northwards before ultimately drawing cold air down across the USA. This in turn forced a particularly strong and persistent Jet Stream across the Atlantic and towards the UK. The Met Office is now studying this sequence of events in significantly more detail. In our paper, we show how the winter storms affected river flows, and place the events within a historical context.

Flooding in Oxfordshire, February 2014. Photo: Julia Lawrence

Second, questions mount as to whether fossil fuel burning could have a role. We have reviewed existing research literature for Earth system factors that may be both changing through global warming, and additionally are identified as influences on storm features for the UK. As expected, this confirms how complex and inter connected the climate system is. Multiple possible UK rainfall drivers are identified that link to the state of the oceans, the atmosphere and sea-ice extent. Interestingly the recent rapid decrease in Arctic sea-ice that is widely attributed to global warming, for the UK at least is often portrayed as likely to bring more Easterly winds and colder conditions. The previous three winters had these features for some of the time, in marked contrast to winter 2013/14. Although the precise details of linkages between changing large-scale features of the climate system and UK rainfall intensity are still not fully understood, we hope our review article is a complete list of such connections. To apply that frequently used expression, we trust there are no “unknown unknowns” lurking out there we have yet to consider.

Third, we provide some thoughts on how best to proceed. Assuming that we do have a pretty good idea of all drivers expected to affect rainfall, and that require on-going computer modelling, three challenges are noted. These are: (1) the need for continued enhancement of physical process representation via ever better parameterized differential equations of the oceans, atmosphere and ice sheets, (2) increase further the numerical grid resolution of climate models, on which these equations are calculated and (3) undertake significantly higher numbers of simulations, all with slightly different initial conditions, creating a large ensemble of projections. The call for better resolution is because some characteristics of storms occur on fine spatial detail, thus needing small spacings between gridpoints on which calculations are updated. The request for large ensembles is because extremes, by definition, are rare events, and so we need to ensure that all heavy rainfall “return times” are fully sampled. This is both for pre-industrial and for raised levels of atmospheric greenhouse gases.

During the major flood events affecting much of Southern England from December 2013 to February 2014, it was inevitable that questions would be asked as to whether fossil burning could have a role. It is always (and correctly) stated that no single observed extreme event can be formally attributed to human-induced changes to atmospheric composition. But a statistic can be derived that assesses any changing probability of a particular extreme event occurring, a quantity sometimes referred to as “Fractional Attributable Risk”. By satisfying the three challenges we listed above, we will get near to stating if humans are increasing, decreasing or leaving invariant the chances of rainfall events of the type witnessed. However, even now limitations remain on computer speed and resource, and expenditure on climate research can only ever be finite. Hence an especially lively debate will now occur as to what constitutes the optimal balance between pursuing these three challenges, in order to get us most quickly towards the required answers.

Anyone studying meteorological systems, or the full Earth system, soon realizes of course how tightly coupled all features are of the climate system. In this review, by trying to collate in to a single paper the main factors affecting UK rainfall, this did though provide a timely reminder of such comprehensive interconnections. Understanding these further suggests a very interesting time lies ahead for climate change research.

Chris Huntingford

Chris Huntingford is a climate modeller based at the Centre for Ecology & Hydrology in Wallingford, Oxfordshire.

Additional information

Full paper reference: Chris Huntingford, Terry Marsh, Adam A. Scaife, Elizabeth J. Kendon, Jamie Hannaford, Alison L. Kay, Mike Lockwood, Christel Prudhomme, Nick S. Reynard, Simon Parry, Jason A. Lowe, James A. Screen, Helen C. Ward, Malcolm Roberts, Peter A. Stott, Vicky A. Bell, Mark Bailey, Alan Jenkins, Tim Legg, Friederike E. L. Otto, Neil Massey, Nathalie Schaller, Julia Slingo and Myles R. Allen (2014) Potential influences on the United Kingdom’s floods of winter 2013/14. Nature Climate Change, doi:10.1038/NCLIMATE2314

Staff page and research interests of Chris Huntingford 

New scientific review investigates potential influences on recent UK winter floods  (CEH News, 27 August 2014)

Surface water flood risk forecasting system operational in Glasgow as Commonwealth Games begin

As the 2014 Commonwealth Games get underway in Glasgow today (23 July 2014), organisers are probably hoping the next two weeks will stay dry and pleasant for everyone travelling to and from the various locations being used across the city. However, they’ll still be interested in the news that the Glasgow surface water flood forecasting model became operational this month – thought to provide the UK’s first operational grid-based surface water flood risk forecast with a 24-hour lead time.

Surface water flooding occurs when rainfall is unable to enter a watercourse or artificial drainage system and instead ponds or flows across the surface. In Scotland, the National Flood Risk Assessment (NFRA) estimates that 38% of flooding impacts are due to surface water (NFRA, 2011). Providing real-time surface water flood risk forecasts is challenging due to the dominant meteorological driver being convective storms, which are often highly localised and notoriously difficult to forecast.

Hampden Park is one of the venues for the 2014 Commonwealth Games in Glasgow.
Photo by Jmorrison230582 in public domain.

The new surface water flood risk forecasting system has been developed by the Scottish Flood Forecasting Service (a strategic partnership between the Scottish Environment Protection Agency (SEPA) and the Met Office), working with the Centre for Ecology & Hydrology (CEH), Deltares and James Hutton Institute. The system builds on complementary CEH research on surface water flooding that is co-funded by the Environment Agency and undertaken within the Natural Hazards Partnership.

CEH’s Grid-to-Grid model (Moore et al., 2006, 2007; Bell et al., 2009) is a key component of the new tool. CEH scientists Bob Moore and Steve Cole provided pre-operational training in the system to SEPA and Met Office staff.

Steve Cole highlighted that, “Due to high uncertainty in forecasting the precise location of rainfall, particularly in convective situations, a probabilistic ensemble approach has been needed for the new Glasgow surface water flood risk forecast tool. A particularly novel aspect is that the tool goes beyond forecasting the likely location of surface water flooding to embrace information on potential impacts on people, property and transport. This should help emergency responders make more timely and better informed decisions.”

Further information on the new system is available from the Scottish Flood Forecasting Service, who provide regular progress updates:

• Operational surface water flood forecasting model for Glasgow now live (July 2014)

• Surface water flood alerting: project update (November 2013)

• Surface water flood alerting for the Commonwealth Games (July 2013)

More information on the Centre of Expertise for Waters (CREW) project

Surface water flood forecasting for urban communities
 

Winter 2013/14 rainfall records at CEH's Wallingford meteorological station

Katie Muchan, a hydrologist with the Centre for Ecology & Hydrology, looks at the 2013/14 winter rainfall totals recorded at CEH's meteorological station at Wallingford, Oxfordshire.

The news for the last three months has been dominated by record rainfall and prolonged flooding. It was the wettest winter for England & Wales since records began in 1766; and in south-east England, 2013/2014 winter rainfall in both the Thames and Southern regions was more than 230% of the average. The story for the meteorological station based at CEH’s Wallingford site has been no different, with several rainfall records broken during the winter of 2013/2014.

Daily temperature, rainfall and sunshine have been recorded at the meteorological station at the Wallingford site since 1962, in addition to observations of cloud cover, present weather and visibility. The persistence of the storms through the winter of 2013/2014 can be seen in the daily rainfall data. Once the storms started on 15 December 2013, rainfall was recorded on 73 of the 76 remaining days of winter. Furthermore, 66 of these 76 days can be classed as a rain-day, defined as a day when at least 0.2mm rainfall is recorded.

Daily rainfall (mm) during winter 2013/2014 at CEH's Wallingford meteorological station

December started dry, with only 2mm of rainfall recorded in the first two weeks. However, following the first storm on the 15th, rainfall was recorded on all but one day for the rest of the month and the most notable storm, on the 23rd, recorded a daily rainfall total of 35.5mm (36% of the monthly total). This made it the wettest day of the year, and also the wettest day since 22 August 2010. Due to the dry start to the month, December 2013 rainfall was not record-breaking, but it was the fifth wettest in the station’s history, with a monthly total of 97.9mm.

The persistent rain continued into January; only two days recorded no rainfall. As a result, January was the wettest of the winter months; the monthly total of 148.4mm broke the previous January record by 30mm (~25%). January 2014 was also the third wettest of any month at the station in the record from 1962, behind August 1977 and October 1966.

February is normally the driest month of the year with an average monthly total of 37.5mm. However, with rain falling every day in February 2014, yet another record was broken. The monthly total of 112.9mm is 302% (i.e. three times) the average, making it the wettest February in the station’s history (beating the previous record of 103.3mm in 1990).

*Previous records are quoted based on data for January 1962 - November 2013

While the individual monthly totals and records are impressive in themselves, the accumulation of rainfall across the winter season also produces some record-breaking figures. The rainfall total of 246.3mm in December 2013 and January 2014 set a record for the wettest two-month accumulation of any in the station's history, only to be broken by the rainfall in January and February 2014, which totalled 261.3mm. On 13 February, with 15 days of winter remaining, the record for the wettest winter set in 1989/1990 (311.5mm) had already been broken. Rain continued throughout the rest of the month, giving a 2013/2014 winter total of 359.2mm, breaking the previous record by 47.7mm.

Winter rainfall totals (mm) at CEH's Wallingford Meteorological Station

Katie Muchan

Additional information

More information on CEH's Wallingford meteorological station

Hydrological Summaries published during winter 2013/14, including the February 2014 Hydrological Summary

A joint Met Office and CEH report on the winter storms and floods was published in February.

Scientists from CEH comment on the ongoing flooding situation in the UK - 13 February 2014

Scientists from the Centre for Ecology & Hydrology have provided the following new comments on the ongoing storms and flooding situation in the UK.

You can read our previous comments (published on the 11 February 2014) here.

Prof Richard Harding,  Centre for Ecology & Hydrology, on the December/January/February floods

"The weather in the last two months has been exceptional. It has been characterised by frequent rain systems tracking across the south of Britain, often associated with high winds. In January the rainfall totals were locally 300% above average and over 200% over a large part of southern England. The result of this relentless rainfall has been that soils and underlying aquifers are now full and the rivers and wetlands have more water flowing through them than has been observed for many decades.

"The repeated passage of storms over England has been caused by a persistent Jet stream to the south of its usual position. This persistence may be linked to the reduction of sea ice in the Arctic or warm sub-tropical sea temperatures. We have observed in the last five decades a rise in temperatures and an increase in the amount of water vapour in the atmosphere – these almost inevitably lead to an intensification of storms and increases in rainfall. Indeed we have observed an increase in the intensity of rainfall in this period. The last two decades have also brought exceptional extremes in our rivers and groundwater– with floods in 2000/01, 2002/3, 2007, 20011/12 and now 2013/14 interspersed with droughts in 2003 and 2011/12. All these trends are entirely consistent with the effects of increasing CO2 in the atmosphere.

"In the short term the saturated nature of the ground means that rivers and low lying areas are very vulnerable to flooding. In the longer term this exceptional weather and extensive floods highlights that we are going to have to adapt to much more variability and extremes in the future."

Mr Nick Reynard, Science Area Lead for Natural Hazards, Centre for Ecology & Hydrology

"After the devastating summer floods of 2007 the Pitt Review carefully analysed all aspects of how this country prepares for and deals with flooding. Post Pitt there have been two key developments in the implementation of flood forecasting science to better predict both the risks and impact of flood events. The first is the development of the Flood Forecasting Centre, which combines meteorological and hydrological expertise to provide forecasts for all natural forms of flooding - river, surface water, tidal/coastal and groundwater. River flow forecasting is underpinned by the Grid 2 Grid model developed by the Centre for Ecology & Hydrology.

The second significant development has been an increased focus on surface water flooding - many of the 55,000 homes affected in 2007 were flooded by a surface water event. Surface water flooding is a key focus of the recently formed Natural Hazards Partnership, which provides information, advice and analysis to government and emergency responders across the UK in the preparation, response and review of natural hazards. and brings together expertise from across the UK's leading public sector agencies and research institutes."

Mr Terry Marsh, Leader of the National Hydrological Monitoring Programme, Centre for Ecology & Hydrology

"The tempestuous weather affecting the UK has continued through the first two weeks of February 2014. It appears likely that winter rainfall totals across much of Southern Britain will be the highest on record (in the NCIC series from 1910). As a result river flows have continued to increase in parts of the country, most notably in the Thames and the Severn basins. In recent days on the Thames river flows are approaching or have exceeded maxima recorded in the last major event (November 1974). The high river flows have led to extensive floodplain inundations aggravated by groundwater flooding in many vulnerable parts of the catchment."

Scientists from CEH and BGS comment on the ongoing flooding situation in the UK - 11 February 2014

Scientists from the Centre for Ecology & Hydrology and their NERC colleagues in the British Geological Survey have provided the following comments on the ongoing storms and flooding situation in the UK.

We published further comments on 13 February 2014. Read them here.


Mr Terry Marsh, Leader of the National Hydrological Monitoring Programme, Centre for Ecology & Hydrology

"One of the issues for the public perception to take on board is what we are currently seeing is the Thames exercising its natural sovereignty over its floodplain. This happens occasionally and in a sense it’s good for people to recognise that this happens. Management needs to limit the damage but it would be, I suggest, even worse if we found ourselves in the position where people thought because we’ve not seen this extent of flooding for 40 years that it’s not going to happen. It’s a natural part of the way rainfall patterns translate into river flow patterns."

Dr David Boorman, Science Area Lead for Water Resources, Centre for Ecology & Hydrology

"A key question in any unusual hydrological situation, such as a drought or a period of wet weather as we are experiencing now, is how long will it continue? We are working with a number of partners to provide a long-range hydrological forecast for the UK. Forecasts of this type are already produced on an operational basis in a number of countries including the USA and Australia.

“The project involves bringing together information on the current weather, soil moisture, river flows and groundwater levels from across the UK, and using a number of methods of exploring possible future hydrological conditions, for example, using numerical models of river flows and groundwater models driven by long-range weather outlooks."

Mr Nick Reynard, Science Area Lead for Natural Hazards, Centre for Ecology & Hydrology

"The cluster of drought and flood events through the early years of the 21st century and the recent runoff and recharge patterns, are near to the extreme range of historical variability as we currently understand it , and therefore also raise the question that they may reflect anthropogenic climate change. It is important to note, however that how river flows respond to extreme rainfall varies greatly because of geology, soils, land use etc, meaning that it is difficult to detect signals of climate change in observed events, and to generalise the impacts of climate change for future flooding. Tidal flood risk is increasing as sea levels rise but the outlook is more complex in relation to fluvial flooding."

Prof Alan Jenkins, Director of Water and Pollution Science, Centre for Ecology & Hydrology

"The long duration of the current flooding episode and its wide spatial extent make it an exceptional event. Relentless storm events over many weeks have combined to produce widespread flooding at a scale rarely seen in the UK. Over 5000 homes have flooded and transport infrastructure has been disrupted across the UK.

“The key to mitigating the impact of any flood is understanding that every catchment works in a different way. For example the current flood situation on the Somerset Levels is the result of a different range of processes to those currently affecting the lower reaches of the River Thames. The operational agencies are doing a sterling job on the ground and it’s important to recognise that hundreds of thousands of homes have been protected by the UK’s flood defence infrastructure.

“Many potential solutions have been talked about over the last few weeks as ways of minimising flood risk. This is a complex issue and over the next few months it is important that experts from the key agencies and research institutes sit down and carefully analyse whether there are lessons to be learnt from the current flood episode."

Dr Chris Huntingford, Climate Modeller, Centre for Ecology & Hydrology

"In terms of climate change, there is a desperate need to move away from the almost Punch-and-Judy debate of either every extreme is due to climate change, or the contrast of everything is simply natural variability. Desperately needed is the on-going calculation of whether higher atmospheric concentrations of carbon dioxide are changing the chances of rainfall events, as recently witnessed, occurring.

To work this out, weather forecast models that analyse the atmosphere in such fine detail as to model storm tracks, need to be operated for different levels of modelled carbon dioxide. Running these for hundreds of modelled years for alternative carbon dioxide concentrations, so as to build up statistical profiles of rainfall patterns, presents one of the biggest computational challenges ever tackled."

Mr Simon Parry, Hydrologist, Centre for Ecology & Hydrology

"Each one of these individual events has not been particularly outstanding, they've been broadly along the lines of what we would expect for a typical winter storm in the UK. What's been notable about it, and different from what we've seen in the past, is the persistence. The combination of high tides, strong winds and a succession of rain-bearing low pressure systems has led to widespread and sustained high flow conditions over a two month timeframe."

Mr Andrew McKenzie, Groundwater Information Manager, British Geological Survey

"In early December 2013 groundwater levels over much of the UK were normal for the time of year. The extreme rainfall in the southern part of England over the New Year and into early January had a dramatic impact on levels in the faster responding aquifers and spectacular rises occurred in groundwater levels in some aquifers. For example, groundwater levels in the Chalk at Tilshead on Salisbury Plain rose by about 20 metres in just two weeks. These rapid rises triggered some localised groundwater flooding, mainly in the upper parts of Chalk catchments. If rainfall had eased at that point the empty storage in the lower catchment might have been able to absorb the inflows. However, as rainfall has continued to fall the lower parts of many catchments have been saturated, and prolonged high river levels will have contributed to exceptional recharge.

“At the beginning of February record monthly groundwater levels were measured across many aquifers, and as levels in February are naturally high, these records are often all time records for the sites concerned. Record levels were established in the Chalk of Wessex, the North Downs and Hampshire. The wet weather also reversed a declining trend in some of the North West Permo-Triassic aquifers.

“Consequently, emergence of groundwater has been observed at many localities across southern England where groundwater flooding has been previously recorded. The high water levels on the interfluves (the upper parts of groundwater catchments) will gradually feed into the lower parts of the catchments, over a period of weeks to months, so groundwater flooding is expected to persist."

Additional information

Journalists can contact the CEH Press Office or the BGS Press Office for further context on the UK's hydrological situation. 

Further information from CEH can be found in the following blog posts:

Record breakers? Climate change, statistics and the recent UK floods - 9 February 2014

Rainfall, UK floods and the potential impacts of climate change? - 6 January 2014

CEH worked with the Met Office on a report on the recent storms and floods in the UK.

Record breakers? Climate change, statistics and the recent UK floods

This morning the Met Office and the Centre for Ecology & Hydrology released a report on the recent storms and floods in the UK.

You can read the full report here, and a short summary of the hydrological analysis on our website here. 

The report documents the recent record-breaking weather and flooding episode, and discusses whether climate change contributed to the severity of the weather and its impacts. Climatology, meteorology and hydrology are covered in the report. 

In this blog post we highlight some of the hydrological conclusions that came from analysis of the long-term datasets held at CEH and our long history of research into floods.

With regard to the record-breaking nature of the flooding the report makes the following points:

• The full gamut of flood manifestations – tidal, pluvial (flash), fluvial and groundwater – has been experienced over the last eight weeks.
• The exceptional run of severe winter storms over December 2013 and January 2014 carried with them large amounts of rain which has led to very serious flooding across southern England. 
• Estimated outflows (river flows) from Great Britain remained close to the highest ever recorded during late December and, subsequently, throughout most of January across large parts of England and Wales.
• In a series from 1883, flows on the River Thames at Kingston (close to the tidal limit) remained above 275 m3 s-1 for longer than in any previous flood episode, and continue to exceed this threshold into early February. 
• A preliminary analysis suggest that outflows aggregated over six weeks were the greatest since the 1947 floods – the most extensive in England & Wales during the 20th century.
• In December and January, a few rivers (including the Mole, Wey and Medway, which, on the basis of preliminary data, recorded their highest flows since the extreme floods of September 1968) registered outstanding maximum flows. 
• Generally, however, the peak flows registered during the recent flooding were not extreme. On the Thames the highest flow in 2014 has been exceeded during 14 earlier floods (most prior to 1950). 
• The floodplain inundations across the UK caused major disruption to transport, agriculture and restricted sporting and recreational activities, and resulted in severe difficulties for some low-lying hamlets (most notably in the Somerset Levels). However, given the overall volume of runoff, the amount of property flooding at the national scale was relatively modest; a tribute to the general effectiveness of flood defences.

Figure 1: Combined flows (m3 s-1; black) for the Thames, Severn, Trent, Yorkshire Ouse and Usk in 2013 and January 2014, plotted against period of record (1969-2013) daily maximum flows (blue), daily minimum flows (pink) and daily mean flows (grey)

With regard to whether climate change has been a contributing factor to the current flooding the report states:

• The cluster of drought and flood events through the early years of the 21st century and the recent runoff and recharge patterns, are near to the extreme range of historical variability, and therefore also raise the question that they may reflect anthropogenic climate change. It is important to note, however, that differing flood types may be expected to respond differently to increasing temperatures. Tidal flood risk is increasing as sea levels rise but the outlook is more complex in relation to fluvial flooding.
• Published studies have observed increased river flows in the winter half-year and a tendency for higher flows to occur more frequently, and this has been reinforced in recent years. Importantly, however, such a trend may not be accompanied by any increase in magnitude of major flood events. In the UK, no positive trend in water-year maxima was found in the 130-year series for the Thames.
• Enhanced groundwater flood risk may be expected if average winter rainfall in the UK increases. Flash flooding, which can be exacerbated by land management and land use practices (particularly the extension of impermeable areas), may also increase if the recent intensification in rainfall translates into an enduring trend. 

Much more detail can be found in the full report. More information about the report's conclusions is available on the Met Office website here.

Journalists can call our Press Office if more information is needed on the hydrological conclusions.

Barnaby Smith, CEH Media Relations Manager

Further links

Jamie Hannaford from the Centre for Ecology & Hydrology contributed a chapter to the Living with Environmental Change climate change report card for water entitled, "Observed long-term changes in UK river flow patterns: a review"

An interim update on the UK's hydrological situation - issued by CEH on 6 January 2014

Rainfall, UK floods and the potential impacts of climate change? - blog from 6 January 2014

NB: the Met Office updated the report on 11 February to give a more detailed assessment of sea level rise

National hydrometric data - what does the future bring for the UK's NRFA?

In two previous blog posts this month, we explored how the hydrometric data held by the National River Flow Archive and the National Groundwater Level Archive have been used in past and present scientific research, and how such a valuable data resource is vital for taking a long view of both hydrological trends and significant one-off events. Our series has coincided with a special meeting, on Tuesday 22 October 2013, to celebrate 30 years of the NRFA being hosted at CEH's Wallingford site. To conclude the series, Jamie Hannaford, head of the National River Flow Archive, looks to the future and at what the next few years might bring...

The past 30 years have seen incredible change in how we do our jobs, most obviously in the technology used to gather and disseminate hydrometric data. The next 30 years will undoubtedly see huge change again. When you think about it, 30 years is a generational timescale, it's a career span, it's a period that can expect to see life-changing developments. Hydrometric data and analysis is already important to society for underpinning effective water management, but it will assume even greater importance in global water management over the next 30 years, thanks to the challenges of population growth and movement, land use change and of climate change leading to an intensification of the hydrological cycle.

The NRFA, as the UK's national hydrometric information service, will be crucial to meeting these challenges, lying as it does at the heart of the hydrometric information lifecycle and managing as it does a long-term archive that will be able to take an ever longer view of events such as the 2010-2012 drought to flood transformation. Reliable, easily accessible, contextualised data and analysis will play a key role as scientists and water practitioners meet the world's water resource management needs.

The NRFA already provides its data and analysis in many formats

From the original print publications the NRFA delivered in the 1980s, to the digital outputs it now provides, our data is already, and will continue to be, served in many formats, but our fundamental maxim will always be to turn the data into valuable information. We always make sure we know where the data is coming from, so we can guide our end users.

The technological landscape will certainly continue to develop. Will we be a nation of armchair hydrologists by 2043? In some respects, thanks to remote sensing and satellite capabilities, it's possible to some extent now. But as well as opportunities, technology brings its own challenges - both in the huge amount of data that can be gathered and in the interpretation and validation of that data. For all the hydrometric data that can be gathered, we still need to understand what it is telling us. And we still need our monitoring partners to collect data first-hand to complement the models and the satellite technology.

The provision of reliable hydrometric data in the 21st century will be
crucial for global water management

Future developments

An important area for the NRFA now is to look at how to integrate our river flow data with other types of monitoring, for example near real-time soil moisture data, citizen science initiatives etc, to build up a fuller environmental picture. Our role will be to bring these other types of information together with the river flows; to help with interpreting and understanding them in context with other environmental variables.

Currently we are reviewing our hydrological summaries and looking at different options for enhancement, for example using the best modelling capabilities from CEH and other organisations to deliver improved outlooks and better drought indicators. We are working more closely than ever with international colleagues in organisations such as the US National Drought Mitigation Center and CSIRO in Australia, and aim to improve the information that we and other national hydrometric data providers can supply. It is a challenging task to undertake when hydrometric networks are under pressure worldwide, along with the resources for long-term monitoring.

In the shorter term, you can expect the NRFA to offer daily catchment rainfall on its website from next year. We will also be taking on the validation for HiFlows-UK, the UK's principal source of flood peak data, and making this available from our website in the near future.

Who can really say what the NRFA in 2043 will look like? The last 30 years have been a tremendous effort of stewardship, and the next 30 years will be also, but we are ready and able for the challenge, thanks to the support of our partners. Our data and analysis has informed the likes of the Pitt Review on flooding, which followed the 2007 summer floods, as well as the National Ecosystem Assessment and the IPCC's recent 2013 climate change assessment. We will continue to give that much needed national, strategic assessment that is crucial for water management in this country.

Jamie Hannaford

Additional reading

Dixon, H, Hannaford, J and Fry, M J, 2013, The effective management of national hydrometric data: experiences from the United Kingdom. Hydrological Sciences Journal.

The 2010-2012 drought and subsequent extensive flooding - a remarkable hydrological transformation by Terry Marsh, Simon Parry, Mike Kendon & Jamie Hannaford. 2013. PDF [7.05mb]

Hydrometric data - the long view (first in our special blog series on the NRFA and hydrometric data)

An unprecedented hydrological transformation (second in our blog series)

View photos from the NRFA 30th anniversary event on Flickr

Related links

National River Flow Archive

Staff page of Jamie Hannaford, CEH

An unprecedented hydrological transformation

A huge number of scientific papers have delved into the extraordinary data held by the National River Flow Archive and National Groundwater Level Archive. As our blog series on hydrometric data continues, Simon Parry of CEH (right) discusses one of the most recent papers to use the data, newly published in the Weather journal, which analyses the dramatic transformation from drought to flood in the UK during the summer of 2012.

Whilst this year's fine and dry summer was very much welcome, it was not typical of the more unsettled summers of the last few years. Although the Olympic and Paralympic Games in 2012 were spared the worst of the weather, from April 2012 onwards a succession of wet fronts drenched the UK, in particular England & Wales, resulting in the wettest year for more than a century.

This episode emphatically put to an end concerns about the water resources situation, which saw hosepipe bans implemented in April across south, central and eastern England affecting 20 million consumers. Recent research by CEH scientists, in collaboration with the UK Met Office, published last month in Weather, finds that the transformation from drought to floods in England & Wales is without modern parallel in the historical record (Parry et al. 2013).

The extreme drought of 1975-76 remains the most severe in the historical record, most likely the worst experienced in the UK for at least the last 250 years (Rodda & Marsh 2011). This episode was terminated dramatically in September and October 1976, over which time England & Wales received almost double the long-term average rainfall.

The 2010-12 drought did not reach the same intensity as 1975-76 (Kendon et al. 2013); the summers were not hot or particularly dry in 2010-12, in contrast with heatwave-dominated droughts in 1976 and 2003. However, the rainfall shortages were concentrated in the winter half-years (October-March), a vital time for the recovery of water resources and, as such, outflows from England & Wales in March 2012 were lower than the corresponding point in 1976. Hosepipe bans were implemented in several areas at the end of the normal groundwater recharge season (April); there was little prospect of improvement in the water resources situation, barring something extraordinary happening...

Something extraordinary did happen. Whilst the transformation in 2012 may not have been as spectacular in rainfall terms as that of 1976, England & Wales recorded new record rainfall (series from 1766; Alexander & Jones 2001) for April, June and the summer half-year (April-September), and April-December 2012 was the wettest of any nine-month period in ~250 years.

Flood damage in England, December 2012. Photo: Heather Lowther

Groundwater recharge through the summer half-year

The most important impact of the succession of rain-bearing frontal systems was to re-wet soils which allowed the replenishment of groundwater to resume. What made the transformation in 2012 particularly unprecedented was the resumption of groundwater recharge through the summer half-year; the patterns of hydrological response tracked in the opposite direction to normal seasonal conditions.

Perhaps owing to the British preoccupation with the weather, much attention is given to rainfall figures in characterising the water situation in this country. However, water resources are more complex than this; the relationship between rainfall and runoff is not one-to-one, owing to catchment characteristics and antecedent conditions.

The distinction between a transformation in rainfall and the unprecedented hydrological transformation is an important one; the former would not necessarily have terminated hydrological drought conditions, but the latter did so emphatically. If there had been no concurrent response in groundwater levels following the rainfall, it is likely that hosepipe bans would have remained in place even through a moderately wet summer. This would have been a difficult message for the water companies to communicate to the public, so perhaps the industry was happy on more than one level to have witnessed a hydrological transformation without modern parallel.

Simon Parry

Simon Parry is a hydrologist based at the Centre for Ecology & Hydrology's Wallingford site.

 

References

Alexander, L V, and Jones, P D (2001) Updated precipitation series for the UK and discussion of recent extremes. Atmospheric Science Letters, 1, 142-150.

Kendon, M, Marsh, T and Parry, S (2013) The 2010-2012 drought in England and Wales. Weather, 68 (4), 88-95.

Parry, S, Marsh, T and Kendon, M (2013) 2012: from drought to floods in England and Wales. Weather, 68 (10), 268-274.

Rodda, J C and Marsh, T J (2011) The 1975-76 drought - a contemporary and retrospective review, Centre for Ecology & Hydrology. 58pp. [PDF, 13mb]

Additional information

A comprehensive report by Terry Marsh, Simon Parry and Jamie Hannaford, in collaboration with Mike Kendon (Met Office), on the 2010-12 drought and subsequent hydrological transformation will be published later this month and will be available to download freely from the CEH website.

Next in our hydrometric data blog series, Looking forward - where the archives are going next... Watch this space!

Related links

CEH Blog: Hydrometric data - the long view

National River Flow Archive  

Filming at CEH's met site in Wallingford

Alan Jenkins on Sky News at CEH's met site in Wallingford, a photo by CEH Science News on Flickr.

The recent wet weather means the New Year has got off to a busy start for the CEH Press Office, with several requests from media organisations to interview our hydrologists. On the TV side, Sky, BBC and ITV have all been in touch.

Professor Alan Jenkins of the Centre for Ecology & Hydrology was interviewed on January 2 2013 by Sky News (pictured). He spoke about the dramatic transformation from drought to flood seen in the UK in 2012. The interview took place on the meteorological site at CEH's Wallingford, Oxfordshire headquarters. You can watch the interview on the Sky News website.

David Shukman, the BBC's Science editor, also interviewed Prof Jenkins today, Thursday 3 January, for broadcast later today.

Today, also, the Met Office announced (provisional figures) that 2012 was the second wettest year in the UK national record dating back to 1910, and just a few millimetres short of the record set in 2000. It was the wettest year recorded in England however. Just for interest, the aforementioned CEH met site recorded 820mm of precipitation in 2012, the wettest year in a 51-year series (since 1962).

Update Friday 4 January 2013

What is causing Britain's volatile rainfall patterns? Watch the BBC News video featuring Alan Jenkins of CEH and Andrew McKenzie of British Geological Survey.

The video is also part of the BBC News at Ten broadcast available on iPlayer until later today (4 Jan 2013).

BBC Science Editor David Shukman (right) interviews Prof Alan Jenkins



When climate models get it wrong

Guest post by Dr Chris Taylor, Meteorologist, NERC Centre for Ecology & Hydrology

Our recent paper on how rainfall processes are represented in climate models (‘Afternoon rain more likely over drier soils’ published online in Nature this week) led to some interesting headlines around the globe including "Shock. Climate models are too alarmist" (Andrew Bolt’s column in the Melbourne Herald Sun). This is not exactly how I’d express the meaning of the paper!

A key result of our work is that the current models are getting the relationship between rainfall and local soil moisture incorrect, and therefore can end up in a vicious circle of drying soil and reduced rainfall. Representing the processes by which clouds and rain develop within computer models in order to make climate projections over the entire globe for decades hence is tremendously difficult. Until now we didn't have a global observational basis for testing how well the models were predicting this particular aspect of climate. The paper attempts to do this using data from across six continents. Both the paper itself and our press release  go to considerable efforts to provide a balanced report on the research. 

We have a saying in the UK that you shouldn't throw the baby out with the bath-water. There are plenty of people around who jump on any evidence that the models aren't as good as we would like, and instantly move to reject the whole enterprise of climate modelling. We all know the models have to get better, and to get better, scientists need to identify aspects where the models fail. Sometimes communicating that process isn't easy.

Christopher M. Taylor, Richard A. M. de Jeu, Françoise Guichard, Phil P. Harris & Wouter A. Dorigo ‘Afternoon rain more likely over drier soils’ was published in Nature on 12 September 2012.  DOI 10.1038/nature11377