Living in greater Washington, which hasn't experienced much rain recently, and reading of the drought afflicting the New York and Philadelphia watersheds, one finds it surprising that our water supply ran about normal for August.

The U.S. Geological Survey reported that, thanks to heavy rains in the western parts of the basin, the flow of the Potomac River averaged 2.3 billion gallons daily -- exactly normal for the month. Upstream, the flow was above normal; closer to Washington, Potomac tributaries in our own drier area contributed less than normal. But we had enough to drink and bathe in (our average consumption was 383 milllion gallons a day). The range of river flow measured near Washington was from 1.6 billion gallons on Aug. 16 to a high of 3.4 billion gallons on Aug. 23.

The groundwater level at Fairland, in northeastern Montgomery County, was 1.8 feet below the longterm average, a problem chiefly for agriculture.

Significantly, the Susquehanna River, which rises in New York state and Pennsylvania, normally contributes 40 to 50 percent of the fresh water inflow to the Chesapeake Bay. Last month, it was down to 21 percent. The James River, which flows through Richmond, was swollen by rains and carried about twice the Potomac's flow last month, contributing 35 percent, instead of the usual 10 to 20 percent, of fresh water into the bay.