Residents in several Maryland counties are being asked to conserve water and limit non-essential water use.

The notice applies to Baltimore City, Baltimore County, Harford County, Howard County and Carroll County.

Baltimore City officials are citing historically low levels at the Liberty Reservoir, which is one of the region’s main drinking sources. Officials say the Reservoir, which is in eastern Carroll County, has been impacted by below-average rainfall and increased seasonal demand. Water levels at Loch Raven and Prettyboy reservoirs are also declining.

The voluntary restriction applies to customers who use public water and not those who rely on private wells.

With significantly lower than normal seasonal rainfall averages and the high-demand spring and summer seasons underway, leaders at the city’s public works department are concerned with preserving the regional water supply.