Snow Water Equivalent

Snow Water Equivalent is WeGaw's daily dataset of the water stored in the snowpack across a customer's catchments. Hydropower operators and energy traders need to know how much water will reach reservoirs and rivers when snow melts, but simulations driven only by temperature and precipitation, point measurements from weather stations and snow pillows, and occasional field surveys leave large gaps in mountain catchments.

WeGaw first maps snow cover extent by fusing optical and radar satellite data (Copernicus Sentinel-2, MODIS and VIIRS for snow cover) with weather reanalysis and numerical weather predictions using machine learning. It then retrieves snow height by combining Copernicus Sentinel-1 radar, terrain data and in-situ observations from snow measurement stations, and converts snow height to SWE with a customised multi-layer snow density model that tracks the compression of snow layers over time. SWE is delivered daily at 100 m resolution with a one-day lag, as NetCDF or GeoTIFF rasters or as catchment statistics in CSV, through the REST Wegaw API, the Wegaw4Hydro dashboard or SFTP. The Swiss national record runs from October 2017.

WeGaw reports that, in the DeFROST4Hydropower project supported by the Swiss Federal Office of Energy with nine energy companies, integrating its SWE data into rainfall-runoff models reduced long-term seasonal inflow forecast errors by up to 50%. Alpiq reports that, after internal testing, the improved water forecast with snow data could reduce traded volume changes by 5% to 30% and increase income by 0.2% to 1.2%. Enel and the European Space Agency selected WeGaw for an SWE feasibility study on hydropower plants in northern Italy, and WeGaw publishes evaluations of its SWE against independent reference data from Canada, Norway and the United States.