Comparing the last days of August to July, there was a decrease in the amount of water stored in all monitored river basins (which can correspond to more than one reservoir), as shown in the SNIRH data.

By the end of August, the Mondego basin was the one with the highest amount of water available (81.6%), followed by Guadiana (81.4%), Tejo (81.2%), Douro (76.2%), Cavado (75.4%), Ave (74.2%), Barlavento (69.2%), Arade (68.1%), Mira (65.3%), Lima (62.9%) and Sado (60.6%), with Oeste basin registering the lowest number (59.5%).

The water storage of August 2018 per river basin is higher than the averages from August 1990/91 to 2016/17, except the Lima, Ribeiras do Oeste, and Mira basins.