THE LAND and Water Conservation Fund was established by Congress in 1965 to provide an orderly flow of money for the purchase of park land by the federal and state governments.The money comes from the sale of surplus property, taxes on motorboat fuel and off shore oil leases. About $5 billion of it has been spent in the last 15 years to buy almost 3 million acres of land for federal projects and more than 2 million acres for state projects.

Secretary of the Interior James Watt has proposeed putting a moratorium on these purchases and diverting some of the fund's money for "restoration and improvement" of property the federal government already owns. His rationale is that the national parks, and other federal properties, are in a sad and perhaps dangerous state of disrepair, and the government should not buy any more land until it takes better care of what is already has.

Mr. Watt's argument has a superficial logic to it if you accept his premise. But it seems to us that the national parks are not in particularly worse shape now than they were 10 or 20 years ago. Here and there parks do have serious problems -- bad water and sewer systems, decaying buildings and roads. That's nothing new: remember Mission '66, the project of the 1950s and 1960s to get the parks back in first-class condition?

Most of the problems of the parks (and for this purpose we include in that term all federal recreational property) come from overuse. For instance, Rocky Mountain National Park, once one of the gems of the Park Service, is being loved to death, as the Denver Post put it last summer.

The solution to the overuse problem is the acquisition of more park land. That is what the Land and Water Conversation Fund was created to provide. It may be appropriate to take some of the money to bolster the maintenance and repair program. But totally cutting off the land-buying program would be a serious mistake. More than $30 million has been spent in the last three years for example, buying land for the Appalachian Trail; another $50 million would complete this project, which has been under way for decades. If it is not completed soon, the land will be used for other purposes.

By providing a steady flow of money for that and similar projects, state as well as federal, the Land and Water Conservation Fund has made it possible for property owners and local governments to protect key areas from development until their acquisition came to the top of the list. If Congress disrupts that process without any fixed guarantee of when, if ever, it will be resumed -- as Secretary Watt has requested -- that protection is going to slip away, and the land future generations will need for recreation will sprout houses and roads and the other attributes of development.