Burton J. Rubin of the Fairfax County Water Authority claims [op-ed, Aug. 13] that the need for water restrictions is a matter "for professionals rather than one of public policy for politicians." Such arrogance from a representative of a body crucial to the public health and welfare is astounding.

The time is long past when we can consider the Potomac River to be a limitless source of water for residents of the region. An unwillingness to exercise some discipline regarding water use is short-sighted. Prudent resource management during the current drought demands that measures be taken to reduce consumption.

In addition, Rubin ignores the function of the Potomac as an ecosystem. His "use it or lose it" position flies in the face of 20 years of regional focus on the connection between the restoration of the Chesapeake Bay and the freshwater flows from the second-greatest source in the watershed: the Potomac.

Rubin assures us that we need not worry about the environmental health of the river. He fails to mention the lack of biological analysis in the 1981 Maryland Department of Natural Resources study that established the level of environmental "flowby" -- the amount of water necessary to support the ecological functions of the river after water utilities withdraw public supplies. When the department set the flowby volume of 100 million gallons per day, the U.S. Fish and Wildlife Service recommended a flowby between 800 million and 1,200 million gallons per day. Revisiting the flowby number is key to the long-term sustainability of the Potomac as an ecosystem.

Maryland Gov. Parris Glendening and Montgomery County Executive Doug Duncan deserve credit for increasing public awareness of the Potomac as a critical regional resource.

-- Michael S. Nelson

The writer is executive director of the Audubon Naturalist Society.

Burton J. Rubin's statement about "use the water, or lose the water" is not completely accurate.

Rivers and streams have something called "instream flow needs." These are the needs of aquatic creatures for oxygen, habitat, temperature and the other factors that make the stream or river livable.

Fish and other aquatic creatures are often as stressed out during drought and low river flows as land creatures such as ourselves. The more water that remains in a stream or river during drought, the better the chance that its instream flow needs will be met.

And then the freshwater inflow requirements of Chesapeake Bay must be considered. One of the things that make the Chesapeake such a productive ecosystem is the inflow of freshwater from the Potomac, the Susquehanna and other bay tributaries. Reducing flows to the bay upsets the delicate balance of salt and fresh water.

Rubin seems to have lost sight of these other important considerations when he says we don't need to reduce withdrawals from the Potomac River during this intense drought.

-- Richard A. Cairo

The writer is general counsel of the Susquehanna River Basin

Commission.