There is an outflow on water into the river Derwent in the riverside gardens https://www.openstreetmap.org/way/107391475 between these steps https://www.openstreetmap.org/way/180321012 and https://www.openstreetmap.org/way/180320982 route possibly from Albert Street under the council house car park https://www.openstreetmap.org/way/962494720
The Wikipedia article mentions another outflow into the Mill Fleam https://www.openstreetmap.org/way/29291874 near the Mill Fleam pumping station https://waterprojectsonline.com/case-studies/mill-fleam-ps-2023/
Only the entrance near Ford Street https://www.openstreetmap.org/way/278713958 and the exits in the Riverside gardens and Mill Fleam obvious on the ground although the name "Sadlergate Bridge" clearly indicates that the brook flows under here https://www.openstreetmap.org/way/278713958
