According to data from the National Water Resources Information System (SNIRH), 17 of the 59 reservoirs monitored had water availability at the end of December of more than 80 percent of the total volume, while 14 had values below 40 percent.

The Ribeirasdo Barlavento basin had the lowest water availability at the end of December with 21.4 percent.

Next came the Mira (43.1 percent), Sado (47.9 percent), Lima (51.2 percent), Arade (55.2 percent), Oeste (55.3 percent) and Ave (57.3 percent) basins with the lowest water availability.

According to SNIRH data, the Tagus (77.9 percent), Douro (71.7 percent), Mondego (71.3 percent), Cávado (66.3 percent), and Guadiana (64.1 percent) basins had the highest levels of storage at the end of December.

The December2020 storage per river basin is lower than the December storage averages (1990/91 to 2019/20), except for the Douro, Mondego, Tagus and Arade basins.

Each river basin may correspond to more than one reservoir.