Kettle Brook Reservoir Number Four, also known as Bottomly Pond, is part of the Kettle Brook watershed, which drains into the Quinapoxet River. The reservoir is fed by Kettle Brook and several smaller streams. The reservoir has a dam at its southern end, which was built in 1911. 

Kettle Brook Reservoir Number Four is located south of Paxton at the junction of Pleasant Street (MA-122) and Reservoir Road (MA-56).