The release made from Gouthwaite reservoir to the River Nidd is determined by the time of year and level of the reservoir.  The table and graph (see PDFs below) show the rules governing the release.  Using the graph, when the reservoir level is in the pink zone (for example, 9m on 1 January), the release should be 50 Ml/d. The release is changed automatically at about 10.00 am each day, using a controller that checks the current reservoir level, determines what the release should be on that day, and adjusts the release accordingly.  The release is changed only once a day to prevent frequent changes in release when reservoir levels are changing.

 

The reservoir is full above the level of 11.89m deep, and when this level is reached the reservoir spills over the spillway arches.