The National Resources Inventory is a scientifically based analysis of the nation’s land use that has been conducted by the U.S. Department of Agriculture every five years beginning in 1982. The most recent report, based on 1997 data, was released late last year, but is under revision. The results are a statistical extrapolation from on-the-ground surveys.

The NRI defines developed land as including residential, industrial, commercial and institutional land; construction sites; railroad yards, cemeteries; airports; golf courses; parks smaller than 10 acres; and highways, railroads and other transportation facilities that are surrounded by buildings or other urban uses.

Within the Bay watershed, Maryland has 7.4 million acres; Pennsylvania has 14.5 million acres; and Virginia 15.3 million acres. Here’s how development has expanded over that land in the 15 years from 1982-97, according to the NRI.

Acres of Developed Land 1982-1997

Maryland

1982: 894,000

1997: 1,252,000

Change per Year: 23,866

Virginia

1982: 1,215,000

1997: 1,890,700

Change per Year: 45,000

Pennsylvania

1982: 931,000

1997: 1,546,200

Change per Year: 41,000