Governors of the four major Northeast states that rely on the Delaware River for drinking water are expected to declare a drought emergency Thursday and severely restrict the amount of water that can be drawn from the river.

Informed sources here said New York City, which relies upon its Delaware River reservoirs for about half its water supply, is planning to declare its own drought emergency next week. Such a move probably would mean an intensified conservation campaign but no rationing.

A severe shortfall of rain and snow since June has depleted water supplies in many East Coast states, and New York and New Jersey have been among the hardest hit. Nearly 170 communities in New Jersey have had water use restrictions since September. New York City, with an extensive reservoir system at the headwaters of the Delaware and large systems in the Catskills and Westchester County, began to get nervous late last summer.

Usually the city's reservoirs are about 75 percent full at this time of year. Today they are less than 33 percent full and at their lowest levels since late 1968, near the end of a prolonged six-year drought.

Govs. Hugh Carey of New York, Brendan Byrne of New Jersey, Pierre du Pont of Delware and Richard Thornburgh of Pennsylvania -- the formal members of the Delware River Basin Commission -- will meet in Trenton Thursday to declare the emergency. It is the first time the governors, rather than their delegates, have attended a commission meeting since 1975.

Besides New York City, such other urban centers as Philadelphia and Trenton rely on the Delaware River for water.