heavy traffic and avoid the lunch-time closure. However Teddington Lock, which is the most downstream of the Environment Agency locks and separates the long Kingston reach of the non-tidal river from Hampton Court to the tideway, is staffed 24 hours a day. During winter, some locks will be closed for maintenance and the status has to be checked with the Environment Agency. The locks at the upper end of the river, from St John's Lock to King's Lock, are manually operated. All other locks on the Thames are hydraulically operated. All locks, except Teddington, can be operated by boat crews outside manning hours, using the adapted system of "public power", which allows boaters to use the hydraulic machinery at reduced power, except during the hours of darkness. Locks are popular visitor attractions, and many serve refreshments. Locks were often built adjacent to islands and therefore many are situated in remote locations, hard to find and can only be reached on foot. Many locks also have moorings that can be used overnight, and some include electric charging points for electric powered boats. All the locks have obvious access from the Thames Path, except for Whitchurch Lock which is within an island and only accessible by boat; Cookham Lock requires a 1km diversion from the Thames Path; and Marlow Lock requires a short diversion. Weirs The Environment Agency has the responsibility of managing the flow of water along the length of the river to prevent flooding on particular reaches and to maintain navigation depths. The volume and speed of water down the river is managed by adjusting the gates at each weir. Occasionally this can result in a fast stream rendering navigation more hazardous. These conditions are indicated by yellow or red warning boards on the lock gates and the status of all locks is published by the Agency. The Agency cannot legally stop navigation when the red boards are out, but continuing to travel is inadvisable and may invalidate a boater's insurance. Occasionally flooding is unavoidable, and the Agency issues Flood Warnings with three levels of severity - Flood Alert, Flood Warning, and Severe Flood Warning. In recent years the Salmon Conservancy has been installing fish ladders at weirs to allow salmon to travel up river. Today some weirs are often used recreationally by kayakers and canoeists for activities such as whitewater slalom and playboating. Specifically, Hambleden Weir and Boulter's Weir