The Lenthalls Dam is an earth and rockfill embankment dam across the Burrum River, located near , on the Fraser Coast, in the Wide Bay-Burnett region of Queensland, Australia. The impounded reservoir is called Lake Lenthall and its main purpose is the supply of potable water for Hervey Bay and surrounding townships within the Fraser Coast Region. The dam is owned by the Council and administered by Wide Bay Water, a council-owned subsidiary.
Originally called the Burrum No 3 Dam, the dam and lake were named after the pioneering family in the district.
The Lenthalls Dam was constructed in two stages, with Stage 1 completed in 1984 and Stage 2, completed in 2007, which installed the spillway gates and raised the dam wall by . A further upgrade was completed in 2015 and comprised modifications to the spillway gates.
The dam wall is high and long. The resultant reservoir has a maximum capacity of when full and covers , drawn from a relatively small catchment area of . Due to its small size and an average depth of , it takes a short time in moderate rain events to fill Lake Lenthall to 100% capacity. The spillway comprises five controlled gates with an ogee crest and concrete lined chute, capable of handling of water.
In January 2013 due to heavy rain from ex-Tropical Cyclone Oswald, the lake reached its highest recorded level of , that was over the spillway.
The reservoir is stocked with Australian native fish such as barramundi, bass, golden perch and silver perch under the Queensland Governments stocked impoundment permit scheme. Other aquatic species which inhabit the lake include spangled grunter, saratoga, Krefft's turtle, Flinders Ranges mogurnda, rainbow fish, firetail gudgeon, long finned eel and many more. The lake is home to a myriad of reptiles, insects, bird life and mammals. A Stocked Impoundment Permit is required to fish in the dam.
A significant black-breasted buttonquails reside within the dry vine rain forests on the ridges overlooking Lake Lenthall.