The Tagus basin also had a storage level below the September average (1990/91 to 2022/23), although by a small margin, according to the SNIRH.

On the last day of September and compared to the last day of the previous month, there was an increase in the volume stored in two river basins and a decrease in 10, according to the SNIR.

Of the 59 reservoirs monitored, five had water availability above 80% of the total volume and 17 below 40%.

In the Barlavento Algarve river basin, the amount of retained water fell from 16.7% in August to 14.2% in September. This basin continues to be the one with the lowest water reserves.

According to SNIRH data, the Arade basin was at 32.3% at the end of September (34.8% in August).

The amount of water also fell in the Mira basin from 38.4% in August to 37.5% in September.

On the last day of September, the Guadiana (76.6%), Cávado (73.4%), Oeste (72.8%), Douro (70.1%), Mondego (65.8%), Lima and Tejo (61%) basins were those with the highest volume of water.

Each river basin may correspond to more than one reservoir.