140K map prepared for the Web by Jonathan Swinton. This map of the inner section of Hobson's Conduit is from the 1938 book, Hobson's Conduit: The New River at Cambridge commonly called Hobson's River, by WD Bushell. (There's a copy in Cambridge City Library among other places). There is a less pretty but much clearer map in the Royal Commission on Historical Monument's City of Cambridge (reprinted in 1998 and available in Heffer's, for instance) but that's copyright and may be largely derived from this one.
In 1574 Dr. Andrew Perne, Vice-Chancellor, suggested that a stream be diverted from Nine Wells near Shelford through the town and the King's Ditch to relieve the "corrupt air". His scheme was implemented in 1610 as the New River and was a joint enterprise of Town and Gown. Thomas Hobson was just one of the group who planned and carried out the scheme though he did endow a Hobson's Conduit Trust, which still exists (a City Council Engineer is Honorary Engineer to the Trust).
The New River was dug from Vicar's Brook near Long Road to the conduit head at the end of Lensfield Road, where it divided into various branches.
There are many access points to the conduit, generally covered by manholes such as one outside the front of Emmanuel College. Some are for sluices and some are dipping points for public or private use.
The City Council's Drainage Engineer controls the sluices and generally lets
water flow in the open conduits in Trumpington Street & St Andrew's Street
between April and September, avoiding frost and leaves.
Much of the open conduits along each side of St Andrews Street were removed in 1996 as part of the pedestrian improvements though that part of the course is now marked by a gulley and access plates. The rest of this section still runs. It used to run into the King's Ditch (now Hobson Street).
Emmanuel College haven't fed their duckpond from the conduit since 1960.
The Cambridge Green Belt Project has created a three-mile walk along Hobson's Brook.
Cambridge : History