Validation of ICESat-2 ATL13 Version 7 Water Surface Elevation on Small High-Latitude Rivers: A Case Study of the River Dee and River Don, Aberdeenshire, Scotland

Satellite Laser Altimetry represents an attractive opportunity to supplement the sparsely distributed in situ gauge network used to monitor rivers. The performance of satellite laser altimetry on small, high latitude streams has however been characterized as being poor. This research will be validating ICESat-2 ATL13 version 7 measured water surface elevations (WSE) for the River Dee (average channel width of approximately 40 – 60 m) and the River Don (average channel width of approximately 30 m), both located in Aberdeenshire, Scotland using 15 minute stage records provided by the Scottish Environmental Protection Agency (SEPA). From a total of 362 ICESat-2 ATL13 granules collected between October 2018 and November 2025, 1,340 WSE segments were obtained from cloud streamed hdf5 files without storing them locally. For the crossing locations nearest to the gauges, atl13 achieved a mean error of −0.17m and root mean square error of 2.36m on the River Dee, and a mean error of −0.92m and root mean square error of 1.36m on the River Don. The major methodology issue was with the ATL13 V7 segment quality field: column 0 is a packed bitmask (observed values 9–6050), not a simple accept/reject flag as in previous versions; therefore, quality filtering must use columns 1–3. The gauge datum for each location is confirmed through the SEPA station record (Park: 22.59 m AOD; Inverurie: 48.1 m AOD). Therefore, these results show that atl13 V7 can measure wse on rivers that are close to the atl13 nominal width threshold and represent the first published validation benchmarks for icest2 on scottish rivers.