UK Hydrological Drought Explorer

This app allows you to explore historic hydrological droughts in the UK and is an output of the Historic Droughts Project . Droughts have been characterised using the Standardisesd Streamflow Index (SSI). The SSI has been derived from a new dataset of daily streamflow reconstructions. See the About data tab for more information.

The hydrological drought information can be viewed for any of the 303 modelled catchments (naturalised series are also available for the Thames (390010) and the Lee (38001), making 305 SSI series in total). You can view a map of the catchments on the Introduction tab.

The SSI can be calculated for defined accumulation periods where streamflow data are aggregated over the given accumulation periods.

Drought events were extracted from SSI time series. They were defined as months with consecutively negative SSI values with at least one of those months reaching a selected threshold (see Barker et al., 2019 for more information). Droughts shorter than 3 months long were excluded.

NB. These settings will apply to each tab you visit except the Uncertainty analysis tab.


This is a map of the catchments for which hydrological drought information are available. A range of catchments are included, including those that have near-natural and those with artificial influences. Visit the NRFA website to find out more about individual catchments.

On the map below, your selected catchment is highlighted in turquoise and catchments are coloured by region. Regions are used through the app to summarise or show information. The table below lists the regions used, the number of catchments in each region and the modelled area.


View SSI data and the extracted hydrological drought events for your selected catchment and accumulation period:

Select a period to show on the plots below (the default is the full modelled period, 1891-2015):


View the top 10 ranked events for your selected catchment, accumulation period, drought event extraction threshold and drought event characteristic:

NB. When ranking by duration, ties are resolved by ranking those events with the lowest (i.e. most severe) accumulated deficit.

In some cases, fewer than 10 events were extracted from the SSI series and so in these cases, fewer than 10 events will be listed in the table above and shown in the plot below.

This plot shows when the top 10 ranked events in the table above occurred:


Explore the spatial footprint of hydrological droughts 1891-2015 for all 305 catchments for your selected SSI accumulation period and drought event extraction threshold. To see a map of the modelled catchments and the regions, go back to the Introduction tab.

Percent of modelled area in drought (all modelled catchments)


When 100% of the modelled area for all regions is in drought, the bars will reach 900 on the y-axis. You can hover over the graph, click and drag to zoom in and double click or click 'Reset Zoom' to return to the full plot after zooming in.

Select a year to see the percent of modelled area in drought for the start of each season in your selected year.


Some preliminary uncertainty analysis has been done on the reconstructed streamflow data. An ensemble of 500,000 was run for each catchment, from which the best run was extracted and used to calculate the SSI and extract the drought events shown in this app. However, for nine catchments the SSI was calculated and the drought events were also extracted from the top 500 ensemble members. The results of this preliminary analysis are shown on this tab.

This plot shows the SSI calculated from observations held on the NRFA (in orange), the SSI from the best performing model run (green) and 500 best performing ensemble members (shaded green)


You can hover over the graph, click and drag to zoom in and double click or click 'Reset Zoom' to return to the full plot after zooming in.


More information on the data and methods used in the Hydrological Drought Explorer can be found at the references below.

Standardised Streamflow Index (SSI)

For a description of the reconstructed SSI and its application for identifying, characterising and ranking hydrological droughts for near-natural Benchmark catchments, and descriptions of historic events see Barker et al., 2019. Historic hydrological droughts 1891-2015: systematic characterisation for a diverse set of catchments across the UK, Hydrology and Earth System Sciences

For a description of the SSI and its application in the UK using observed streamflow data for Benchmark catchments, and drought event extraction methods, see Barker et al., 2016. From meteorological to hydrological drought using standardised indicators, Hydrology and Earth System Sciences

You can download the reconstructed SSI timeseries used here from the EIDC: Barker et al., 2018. Historic Standardised Streamflow Index (SSI) using Tweedie distribution with standard period 1961-2010 for 303 UK catchments (1891-2015)

NB. In order to download data from the EIDC you will need to register for an account.

Daily streamflow reconstructions

The SSI data shown here have been derrived from the best performing (based an a range of model performance metrics, some of which assess model peformance at low flows) ensemble member from a new dataset of reconstructed (modelled) daily streamflow data (Smith et al., 2018).

for a description of the modelling approach for the reconstructions and and an assessment of model performance and uncertainty for 303 catchments in the UK, see Smith et al., 2019. A multi-objective ensemble approach to hydrological modelling in the UK: an application to historic drought reconstruction, Hydrology and Earth System Sciences

To explore the model performance for the catchments shown in this Hydrological Drought Explorer, see the UK Reconstructed Flow Data Explorer

You can and download the reconstructed daily streamflow data (and find out more about the methods used) from the EIDC: Smith et al., 2018. Historic reconstructions of daily river flow for 303 UK catchments (1891-2015)

NB. In order to download data from the EIDC you will need to register for an account.

UK Benchmark Network

The UK Benchmark Network (UKBN) comprises a subset of gauging stations from the national hydrometric network that are most suited for identification and interpretation of long-term hydrological variability and change. Benchmark catchments can be considered reasonably free from human disturbances such as urbanisation, river engineering, and water abstractions, so are near-natural and hence can be used for detection of climate-driven changes in river flow.

See here for more information on the UKBN

Or see Harrigan et al., 2017. Designation and trend analysis of the updated UK Benchmark Network of river flow stations: the UKBN2 dataset, Hydrology Research

Funding

This research was funded by the RCUK UK Drought and Water Scarcity Programme, via the Historic Droughts project (NERC grant: NE/L01016X/1)

The contents of this site are subject to CC-BY copyright: © UKCEH 2023 Crown Copyright