The summer's prolonged drought continues to deplete the state's water resources.

According to the U.S. Drought Monitor, all of Massachusetts was "abnormally dry" as of last week, and 75 percent of the state was experiencing a severe drought, or worse.

The Quabbin Reservoir, which supplies nearly all of Greater Boston with water, lost 10 billion gallons in August, though at 85.2 percent capacity, it is still within normal operating range, according to the Massachusetts Water Resources Authority.

At a Drought Management Task Force meeting on Aug. 11, MWRA officials said that at its current capacity Quabbin can supply the system's current demand for 4.9 years. The task force is set to meet again on Thursday, Sept. 8.

The Bay State avoids the water shortages common in the western part of the country, but aquifers outside of the Boston area face stressors.

Scituate on Monday reported on its website that its reservoir is 21.52 percent full. The South Shore town's reservoir was 74.2 percent full a year ago.

Residents in the neighboring Cohasset were notified Wednesday of increased "full water restrictions" that take effect Thursday. Due to the lack of rain, officials wrote in an email, "no outside irrigation is allowed at any time." Residents may use a handheld hose to water ornamental plants and vegetable gardens, but may not water between 9 a.m. and 5 p.m., or on Sundays.

Since May 1, the Quabbin has lost about 31 billion gallons, more than enough to fill the diving pool at the Rio de Janeiro Olympics 31,000 times. The flooded valley in western-central Massachusetts can hold as much as 412 billion gallons, and was at 351.1 billion gallons on Wednesday.

The Quabbin also supplies some nearby towns and feeds into the Wachusett Reservoir, in central Massachusetts, as drinking water makes its way to Boston. As of Tuesday, the Wachusett was at 91 percent capacity.

A review of water levels dating back to 2005 posted by the Massachusetts Water Resources Authority shows no prior record of the Quabbin dipping below 86 percent. Its lowest volume over the past decade was February 2013 when it dropped to 86.7 percent.

According to the Environmental Protection Agency, the average American family of four uses 400 gallons of water per day. MWRA reservoirs supply about 200 million gallons per day, and serve 2.2 million people as well as businesses, according to its website.

The World Health Organization recommends a water supply of a little more than 5 gallons per person per day to meet basic hygiene needs and hydration.

There's some rain and scattered thunderstorms in the state's near-term forecast and meteorologists are monitoring an ocean storm that's moving up the East Coast ahead of Labor Day weekend.

Michael Norton contributed reporting.