After about 73 kilometres (45 mi), the river passes just south of the walls of this old Roman city, discharging in average 42 m3/s, and flows south through canyons until the valley widens north of Ourense. The river has been harnessed in reservoirs from Portomarín to Frieira. Along its length, it has the following reservoirs: Belesar with 654 cubic hectometres (530,000 acre⋅ft), Peares with 182 cubic hectometres (148,000 acre⋅ft), Velle with 17 cubic hectometres (14,000 acre⋅ft), Castrelo with 60 cubic hectometres (49,000 acre⋅ft) and Frieira with 44 cubic hectometres (36,000 acre⋅ft).