New drought and vegetation indicators added to the UK Water Resources Portal

The UK Water Resources Portal has been updated with new indicators to give users a broader view of dry weather and its effects across the UK. The additions bring together information on climatic water balance and vegetation condition and health, helping users explore how drought develops and impacts the landscape. 

By viewing these new indicators alongside river flows, groundwater levels, soil moisture and other datasets already available in the Portal, users can build a more complete picture of current and past water resources conditions. The updates support researchers, water managers and anyone interested in understanding drought and water availability across the UK. 

A new addition to the Portal is the Standardised Precipitation Evapotranspiration Index (SPEI). Like the Standardised Precipitation Index (SPI), the SPEI shows whether conditions are wetter or drier than usual over different timescales. However, it also accounts for potential evapotranspiration — the loss of water to the atmosphere from soil, plants and open water — characterising the ‘climatic water balance’. This makes it particularly useful for monitoring drought when low rainfall occurs alongside unusually high temperatures that intensify the dry conditions, as experienced in 2025 and 2026. By including the additional drying effect of heat, SPEI can show the severity and development of these conditions more clearly than a rainfall-only indicator.

These maps show the SPEI for September for different accumulation periods, which shows the climatic water balance over different durations. For example, the SPEI-3 shows the climatic water balance for the last three months ending in September (i.e., from July to September), whilst the SPEI-12 shows the balance over the last year (i.e., October 2025 to September 2026). It’s interesting to see that, despite the very wet winter, in the longer 12- and 24-month accumulation periods, we still see extensive deficits and extremely dry conditions across much of East Anglia.  

The SPI and SPEI data have been derived from the latest version of the HadUK-Grid monthly dataset up to 2025 (currently version 1.3.2.ceda, Met Office et al., 2018), data from 2026 use provisional HadUK data supplied by the Met Office to UKCEH under an Open Government License. 

• Find out more about how the SPI and SPEI is calculated on the Drought indices about page.

The Portal now also includes three satellite-based vegetation indicators, which can help users identify where plants may be experiencing stress and users can compare patterns across the country:

• The Vegetation Condition Index (VCI) shows how green vegetation is compared with the range previously observed at the same location and time of year.  
• The Temperature Condition Index (TCI) highlights unusual land-surface temperatures, which can indicate heat stress.  
• VCI and TCI are combined in the Vegetation Health Index (VHI), providing an overall picture of vegetation condition. 

These maps show one of the new vegetation indices added to the Portal – the Vegetation Health Index (VHI), shown here between March and August 2026. The maps show how vegetation health declined across Great Britain over the summer, especially in Wales and south-west England. These vegetation indices have been derived from MODIS earth observation data.

• Read more about how these indices have been calculated on the Drought indices about page.

We will be making the drought and vegetation indicator datasets up to 2025 available in the final quarter of 2026 via the Environmental Information Data Centre. Data for individual catchments, basins or grid cells can be downloaded from the UK Water Resources Portal. 

• Read how to download data on the About Page. 

These updates have been supported by funding from the Natural Environment Research Council (NERC) as part of the National Capability for UK Challenges (NC-UK) programme and the Indicators to Impacts for drought Surveillance (IRIS) project; and the Co-Centre for Climate + Biodiversity + Water.  

More information on the drought and vegetation indices shown on the UK Water Resources Portal can be found on the Drought indices about page.

Read about the development of the UK Water Resources Portal in the open access paper ‘Dynamic High Resolution Hydrological Status Monitoring in Real-Time: The UK Water Resources Portal’.