A Nationally Consistent Approach to Assessing Accumulated Rainfall Rarity

Accumulated rainfall totals are an important variable for a range of hydrological applications, including monitoring and forecasting, and long-term planning. A new report has been published which identifies the most appropriate, nationally consistent approach to quantifying return periods of long duration rainfall.

A comparison of the suitability of nine distribution families for estimating the relative rarity of accumulated rainfall periods across the UK provides opportunities to further improve the accuracy of return period estimation in many areas such as the water resource planning and the Hydrological Summary for the UK, and elsewhere.

Whilst distribution families that are commonly applied in extreme value estimation, such as the generalised extreme value, were demonstrated to be suitable in a lot of cases, overall Pearson Type III outperformed all other assessed distributions. Closer inspection of the performance on accumulation periods of 12 months or less provided further support for the suitability of Pearson Type III, as did the strong performance of Pearson Type III across accumulation periods, start months and regions.

Presentation of return level plots for two potentially appropriate distribution families demonstrated the sensitivity of return period estimates to distribution family, and thus the importance of this question. With this in mind, the approaches presented in Eastman et. al. (2021) provide opportunities to further improve the accuracy of return period estimation and uncertainty quantification.

The full report is now available

Figure 1 Northumbrian 12-month accumulation period beginning in October: return period plots for The Pearson Type III (pe3) and Generalised Extreme Value (GEV) distributions, with associated 95% confidence interval bands, and highlighted return periods corresponding to 48.09, 45.83, and 44.56 mm of rainfall per month. Points correspond to the Weibull plotting positions of the observed rainfall accumulation data.

REF: Eastman, MichaelParry, SimonSvensson, CeciliaHannaford, Jamie. 2021. A nationally consistent approach to assessing accumulated rainfall rarity. Wallingford, UK Centre for Ecology & Hydrology, 42pp.

About Drought briefing note: Drought monitoring and early warning

A new About Drought briefing note: Drought monitoring and early warning: new developments to meet user needs has been released. The note looks at the monitoring, forecasting and early warning needs for different sectors, the key new tools and strategies for monitoring and forecasting droughts, and highlights the ways that sectors such as water companies, regulatory bodies and the agricultural sector have used these tools so far. The note concludes by presenting applications for potential future uses.

The UK, while typically regarded as a wet country, is vulnerable to drought, particularly in some areas of the south and east. There is, therefore, a need for systems that contribute to robust decision-making relating to drought risk. Such systems need to cater for a diversity of sectoral needs. Based on recent drought research, a new suite of tools and approaches have been developed, leading to some advances in early warning capability in the UK of which the briefing note seeks to highlight.

This is the third of a series of briefs to support improved decision making concerning droughts and water scarcity. Click below to read the briefing note.

Front cover of drought monitoring and early warning brief
Drought monitoring and early warning: new developments to meet user needs – the third of a series of About Drought Briefing notes

Dr Chris Lambert, Supply Demand Senior Technical Advisor, Thames Water

Putting the needs of stakeholders at the heart of drought research

“Climate change is decreasing water availability and this research has definitely demonstrated how that can cause significant problems in water treatment works and has given us a better understanding of different types of water resource options.”

Dr Chris Lambert, Supply Demand Senior Technical Advisor, Thames Water

From the initial proposal for funding in 2014 to the final event on November 7, 2019, About Drought was driven by the needs of the organisations, communities and people who would be relying on the results of its research. Their practical requirements, regulatory restrictions, governance and operational methods have informed the structure, design and accessibility of the datasets and tools.

Even at the stage of drafting the funding proposal Thames Water was invited to review it by MaRIUS’ project leader Jim Hall, Professor of Climate and Environmental Risks at Oxford University.

Matching the needs of water industry, NGOs and government

Chris Lambert, who is responsible for developing Thames Water’s Water Resource Management and Drought plans, joined the MaRIUS Stakeholder Advisory Group (SAG). The aim of drawing this expert group from industry, NGOs and government to steer the project, liaising with MaRIUS’ social and natural scientists, was to ensure its outputs, including the ‘impacts dashboard’, matched the needs of the group in an evolving policy context. This early access proved crucial to the benefits Thames Water has gained.

Chris says: “Being on the SAG as well as being involved in the parts of the project that were relevant to Thames Water, gave me wider visibility of the total work of the project. I had a much better understanding of how we could use some of the research in developing Thames Water’s water supply strategy.

“It led to us commissioning some tailored, specific work that gave us a better insight into the reliability of future water resource development and then we fed into our 2019 Water Resource Management Plan.”

Algae growth impact on reservoirs and abstraction

Of particular interest was the work on algae growth in rivers and ‘drought coincidence’. As a result, Thames Water commissioned its own more detailed research on how projected algae growth could impact on extracting water from reservoirs in conditions of water scarcity or drought, slowing its passage through the filtering system and therefore the speed at which public demand for water could be met.

Thames Water also commissioned the development of a bespoke application from MaRIUS’s water quality research data, focusing on the catchments of the Severn and Thames, and the added likely impact of climate change on water availability.

There are further potential impacts of the timing and positioning of water abstraction, i.e. from the bottom of the river catchment as opposed to higher up, including for the health of the Severn and Thames catchments. The results led to a change in plans for the management regime of Thames Water’s reservoirs.

Climate change is decreasing water availability

Chris says: “If you look into future likely scenarios, climate change is decreasing water availability and this research has definitely demonstrated how that can cause significant problems in water treatment works and has given us a better understanding of different types of water resource options.

“Part of my role is to engage with academic bodies to understand the latest thinking and communicate it internally to our senior executives and board members and to our external stakeholders as well. Another part is ensuring we have effective communication for public and community consultation on our Water Management Plans for the more practical aspects of day-to-day water supply. Through my involvement with MaRIUS and About Drought I have found the events – such as the one-day water suppliers’ feedback workshop in Oxford – very useful in giving me visibility of what has been done and in supporting me in getting internal funding.

“I have been able to follow-up with UK-based speakers who have always been very responsive and my colleagues have also found them very helpful.

“I do think that it would be worthwhile continuing bringing this community together, even if it is just once a year, to keep us up to speed. The work isn’t going to stop just because About Drought has stopped.

“It’s important to ensure the good work that has been done to date continues and doesn’t dry up just because the funding dries up.”

Interview by Sally Stevens

Posted October 2019

A Water Strategy for UK Agriculture

Increasing the farming sector’s resilience to drought and water scarcity risks

Water is at the heart of farming and agri-businesses, particularly in eastern England, the east midlands, and south-east, the driest and most water-stressed areas in the UK. Without water most agri-businesses would simply not survive. Irrigated agriculture supplies the UK’s agri-food industry with substantial quantities of high-quality potatoes, fruit and vegetables. But increasing regulation, droughts and a changing climate all threaten the sustainability of this industry and the rural livelihoods it supports. While other sectors and businesses have water strategies, the agriculture sector does need. Agriculture therefore needs a water strategy to ensure that it receives a fair share of the nation’s available water resources.

To address this need researchers at Cranfield University have been working in partnership with the National Farmers Union (NFU), the UK Irrigation Association (UKIA) and other stakeholders to develop a collective vision. The strategy sets out some guiding principles and proposes actions grouped according to the following themes:

  • Manage current and future demand in abstraction ‘hotspots’
  • Address environmental challenges linked to over-abstraction and climate change
  • Build water infrastructure to provide resilience for farming businesses
  • Promote business growth and support multi-sector stakeholder engagement

Drought and Agriculture Synthesis Report

The Agricultural Synthesis report summarises the key findings that emerged from the five Drought and Water Scarcity programme projects to help the UK agriculture and horticultural sector to better understand, forecast, manage and respond to the challenges posed by droughts and water scarcity. The report summarises how drought and water scarcity affects agriculture, and the consequent impact on rainfed and irrigated agriculture. The report also considers drought forecasting and whether drought and water scarcity impacts can be reduced.

About Drought Download Nov 7th

All the data, all the learnings, all the resources, all in one place!

Thursday, November 7, 2019 from 10 am to 3.30 pm
Location: The Royal Society, London, SW1Y 5AG
Registration: via Eventbrite – free to attend but spaces are limited (note that registration closes on the 23rd of October)
Programme: draft programme (PDF)

Draft programme for the About Drought Download conference (available as PDF from in page link)
Draft programme

About Drought Download is the final event of the 5-year UK Drought and Water Scarcity Research Programme, showcasing the difference our work is already making. Register via Eventbrite – there is no charge for this event, but registration is necessary and spaces are limited. Please note that registration closes on the 23rd of October.

See the draft programme, so you can plan to attend this accessible, stimulating day. The event is aimed at decision-makers in water supply, the energy industry, policy, business, environment, agriculture or the public sector. Visitors can engage with hands-on multi-disciplinary programme outputs, listen to and question programme experts in a wide range of drought-related fields, network with people working on drought, and meet users of the outputs from the programme.

  • How is climate change affecting water supply in the UK?
  • What does it mean for policy and industry?
  • What forecasting breakthroughs have been made & how are these already being used?
  • How can we protect the UK’s natural landscape from water shortage?