Aldenham Reservoir

It was built between 1795 and 1797 by the Grand Junction Canal Company, to control the water levels in the River Colne following the construction of the Grand Junction Canal, and was hand dug by French prisoners of war. An inspection report on the condition of the reservoir's dam in September 2019 revealed it to be a stable structure and in good condition, but requiring longer-term repair. Originally, the reservoir was 65 acre in extent, but following repairs to the dam its surface area was reduced to 55 acre. Since 1973 the reservoir has no longer been required for drinking water.

The reservoir has been used for recreational purposes, including fishing and sailing. However, following an inspection of the dam in 2019, the current owners dropped the water level to reduce pressure on the structure. The sailing club was, as a result, no longer able to sail, handed back its lease in 2020 and departed. This also raised questions about the future use of the reservoir. There have also been suggestions that public access will be reduced with the reservoir fenced off from Aldenham Country Park.