Drought and water-levels

Remote sensing from satellite imagery can be a challenge in cloudy Ireland, with the wealth of images offered freely on NASA and ESA portals often ending up a white mess of fascinating cloudscape. Fortunately clouds do not affect the Synthetic-Aperture Radar (SAR) products provided from ESA’s Sentinel-1 mission. And there are a lot of exciting things to do with them.

When crossing the Rhine in my German hometown of Neuss recently, I saw the effects of this year’s hot summer in the lowest water-levels I’ve seen in a long time, just about enough space for the cargo liners to pass each other. That got me an idea: SAR has proven a great product in flood-mapping, so why not turn it around?

BlessingtonLake

The result is a map of water-levels for the Poulaphouca Reservoir (or Blessington Lake), one of the main reservoirs for the Greater Dublin area (superimposed on one of the rare cloud-free Sentinel-2 images). The map shows the extent of the water surface on the 4th August 2018 (1378 ha, dark blue) and the 2nd August 2017 (1447 ha, light blue), nicely visualising the retreat of the water following this year’s drought compared to a more normal summer (a difference of roughly 60 GAA pitches). Without the lakes bathymetry this of course does not tell us anything about changes in water volume. But it still is a nice showcase for the possibilities of SAR data for mapping water bodies.

Map of the Month for August

We are in the middle of a big restructuring exercise in our lab at the moment. One of the tasks was an audit of our data holdings. My colleague Jesko Zimmermann produced this lovely map showing the geographic distribution of the half a million plus spatial data we hold. Don’t worry we’re not compiling some vast geo-intelligence network- most of the holdings are a from our satellite archive- and most of those are cloudy!

A full resolution version of the Map of the Month can be found here.

 

ESA: From green to brown in a month

With temperatures soaring and no rain to speak of, Europe is in the grip of a heatwave. As this year’s heatwave continues, the Copernicus Sentinel-3 mission reveals once again how the colour of our vegetation has changed in just one month. These two images cover the same area: part of Ireland, the UK, the Netherlands, Belgium, part of Germany and part of France, but the difference between them couldn’t be more striking. The first, captured on 28 June 2018, is predominantly green, depicting healthy vegetation. The second, captured on 25 July 2018, however, is mainly brown, showing just how much the vegetation has changed owing to the long hot dry spell Europe has been enduring over the last weeks.

The Copernicus Sentinel-3 mission also offers a wider view of northern Germany, Denmark and Sweden, showing the stark difference between vegetation on 30 June 2018 and 19 July 2018: European drought.