Anne M. Gorsuch, head of the Environmental Protection Agency, yesterday promised her demoralized employes that, despite "countless press reports and rumors of personnel reductions," none will be fired for budgetary reasons through fiscal 1983.

A major reorganization also has been shelved, according to sources close to Gorsuch.

In an unusual letter to employes, Gorsuch said her announcement "will no doubt dismay those who do not have the best interests of the agency at heart. It is not the stuff of sensational headlines."

She said that under coming budget cuts "we will do a better job--not the same job, but a better job--of protecting the environment," and that there will be "no involuntary separations due to reductions in force."

The announcement surprised environmentalists, who have been predicting a wave of firings at EPA. "It's amazing, a complete victory for us," said Jonathan Lash of the Natural Resources Defense Council (NRDC).

But agency insiders said there have been so many resignations since budget cut rumors began last fall that formal firings will not be needed to achieve the drastically lowered personnel levels in EPA's new budget. There will be some shifting of workers among agency divisions, but no major moves, a top official confirmed.

EPA's fiscal 1983 budget of $961 million calls for 8,645 permanent employes, down 12 percent from the 9,821 authorized this year and 24 percent below 1981 levels, according to leaked budget documents.

But more than 600 persons resigned between October and December, more than 2 percent of all employes each month, double the normal figure. January figures are not yet available, and officials are not sure of the exact number employed at the moment.

The letter also reflected the end of a battle within Gorsuch's inner circle over a proposed major personnel reorganization that would have moved many jobs out of Washington and redefined most major jobs.

Pushed by James Sanderson, a Denver attorney who is Gorsuch's nominee to become her policy chief, the idea was to make bureaucratic chains of command more directly responsible to headquarters.

But other Gorsuch advisers argued successfully that reshuffling now, only six months after an initial reorganization, would fill most key jobs with neophytes. "If we'd done it, we wouldn't have been able to get anything out for 18 months to two years," said one on the winning side.

Suspicious employes noted that the letter did not rule out RIFs in particular offices, which could "bump" many Civil Service workers to lower grade levels.

"She's been very upset about the bad press she's been getting, but this has got to be a trick somehow," one said. "There's no way she can get to the numbers of workers she's got in the budget without moving a lot of people."

Work all but halted at EPA as employes buzzed over the letter, which praised them as full of "imagination, energy, technical skill and managerial savvy." They laughed at Gorsuch's reference to a recent Doonesbury comic strip on an EPA employe threatening to jump off a building ledge, and to an advertisement from the NRDC urging EPA employes not to resign.

There will be future news stories "intended to focus our attention on windowsill politics," Gorsuch wrote. "I will share the facts with you, dispelling the rumors. Hang in there, EPA! Sincerely yours, Anne M. Gorsuch."