NORTHAMPTON — The city’s Department of Public Works announced Thursday that it was implementing nonessential water use restrictions, effective immediately, for users of the Northampton public water supply.

Between 9 a.m. and 5 p.m., washing buildings, parking lots, driveways and sidewalks are banned except as needed to apply paint, preservatives, stucco, pavement and cement. Washing cars is also banned, except by a commercial car wash. During this time, irrigation of lawns and watering of gardens, flowers and other ornamental plants is banned except when using a handheld hose. Irrigation systems may be used outside this time frame.

Unrestricted outdoor water use is allowed between the hours of 5 p.m. and 9 a.m.

The city states that limiting water use, especially non-essential outdoor water use, is needed to ensure a sustainable water supply and to protect stream flow for aquatic life.

The Massachusetts Department of Environmental Protection regulates Northampton’s water supply. When the streamflow in the Mill River drops below 26.3 cubic feet per second, the DEP requires that water use restrictions be enacted for a three-day period or when the DEP Drought Task Force declares Drought Advisory Level 1 or higher.

The ban will be lifted when the streamflow rises above that volume for a week or when the DEP Drought Task Force lifts the Drought Advisory.

Anyone who violates the water use restrictions will be fined $100 for a first offense and $200 for a second and any subsequent offenses.

The city will notify the public when the water restriction is lifted. Visit the DPW website at www.northamptonma.gov/dpw for water conservation tips.