As part of the DRY (Drought Risk and You) project, a field experiment was set up in three river catchments (the Frome in South Gloucestershire, the Don in Yorkshire and the Eden in Fife), to study the effect of reduced rainfall on the growth and biomass production of semi-natural grasslands.
The experiment had four aims: better understanding of how drought might affect UK grasslands; engaging local people in drought science (volunteers/ citizen science); provide a focus for engagement activities; and provide detailed information that could contribute to future hydrological models.
More information about the grassland experiment in the Frome catchment can be found in ‘How will climate change affect permanent pastures? Report on the DRY project rainfall manipulation experiment in the Frome catchment’ Ayling S. (2021).
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.
Figure 1Northumbrian 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.
Climate change projections indicate that extreme events will increase in their frequency and severity in the future. An improved understanding of the drought events of the past can inform current and future management. In this talk, Lucy demonstrates how reconstructed river flows have enabled consistent, national scale characterisation of historic hydrological droughts and how access to current and historic data can support ongoing drought monitoring activities.
The work originates from a number of projects including Historic Droughts and the About Drought programme and you can view the talk below.
Following the wettest February on record earlier this year, last month is set to be declared the driest May in England for 124 years with some water regions warning of potential drought conditions.
The UK Water Resources Portal allows anyone with an interest in current water resources or drought conditions to explore the data both nationally and locally. The portal makes use of very recently published river flow data from the Environment Agency and rainfall data from the Met Office to show the situation across the UK. Alongside historical data and standardised indices, the Portal allows users to put the current situation into a historical context.
The UK Water Resources Portal is one of the outputs from About Drought project. More information and further outputs can be found in the About Drought Handbook.
