The river is 59.4 km long from its source in the
Navarrese
municipality of
Goizueta, and 33 km of it runs through the province of
Gipuzkoa. The average temperature is 13.5 °C (56.3 °F). The seasonal and year-to-year variations in water flow are less marked than in other basins of
Gipuzkoa, and the natural regulation of this basin is very high. The quality of the water is fairly good, despite a slight deterioration downstream near the mouth (moderately good condition) where the city of
San Sebastián lies. However, lately, works have been done on the treatment and cleaning of water resulting in an outstanding environmental recovery.
Upstream river waves The mouth of the Urumea river is known for its upstream river wave, which attracts
river surfers. The phenomenon looks similar to
tidal bores, but it's caused by ocean swells instead of tides. Similar to tidal bores, the waves form in the ocean and travel up the river. ==Fauna==