STILLWATER RESERVOIR — When people in Watertown turn on the tap, much of the water that flows out the faucet starts about 40 miles east — as the crow flies — and 1,200 feet up in the Adirondacks at the Stillwater Reservoir.

This is most apparent during a dry summer. Under those conditions, half of the water in the Black River in Watertown comes from reservoirs in the Adirondacks, and 85 percent of the reservoir water is from Stillwater, which forms the headwaters of the Beaver River. The Hudson River-Black River Regulating District is responsible for storing and influencing the water flow on the Black River and its tributaries.

"We can't control the Black River because we don't have reservoirs everywhere," said the district's executive director, Glenn A. LaFave. "But we can influence and regulate it."

The early spring months are especially tricky for the district as snow melts, filling the reservoirs. At the same time, snowmelt running into tributaries without dams, such as the Deer River, limits how much the district can release to keep rivers from flooding.

This year, the river ran above flood stage in Watertown from April 12 to 14, according to the U.S. Geological Survey Web site.

But without the work of the Hudson River-Black River Regulating District, spring floods would be much worse.

For example, this winter along the Hudson River, the water reached two to five inches above flood stage. Without the district's control of the flow, the flooding would have been four feet, Mr. LaFave said.

That's the district's mission — "to regulate the flows of the Hudson River and Black River for the purposes of flood protection and flow augmentation."

The normal cycle is for the district to release water from its three reservoirs in the Black River watershed during the early winter, recognizing the snow will melt in the spring.

In the Adirondacks this winter, district staff watched the snow pile up without any thaw. "There were a lot of times when the temperature didn't get above freezing," Mr. LaFave said.

Staffers take regular measurements at 13 snow survey sites for amount and water content. At the last measurements, the upper drainage basin had 9.6 inches of snow, which is 68 percent above average. In water content, measurements showed 3.6 inches, or 73 percent above average. Even on April 25, there were piles of dirty snow in the mountains.

Summer is when the reservoirs really show their worth. They try to keep enough flowing from Stillwater to produce electricity at about 25 hydroelectric power plants on the Beaver and Black rivers.

Then the reservoirs rise again with the fall rains.

A MATTER OF CONTROL

On April 25, 1,814 cubic feet per second was gushing out four chutes on the Stillwater dam. That's almost 70 percent of the maximum the dam can release. That amount, if continued over 24 hours, would release about 1.1 billion gallons. The district had to be prepared for more water coming into the reservoir from melting snow in the Adirondacks and forecasts of rain.

Because most of the trees in the watershed do not yet have leaves, they aren't soaking up water. So that water will run into the rivers, too.

"It's hard enough to predict the weather, but we try to go a little further," Mr. LaFave said.

The district has target levels for each of its reservoirs. District staff considers water levels, monitored by automatic survey stations, and weather predictions when deciding how much water to release from the three Adirondack reservoirs.

At Stillwater, the district targets releases of 670 cubic feet per second. The district allows the Mercer hydroelectric power plant, which sits next to the Stillwater dam, to release that amount. That keeps the power plant running at full capacity.

"That level works well all down the river," said Douglas H. Criss, the Black River area superintendent.

For most of the year, that's the outflow from Stillwater and none of the dam's gates need be opened. But at times such as early spring, when Stillwater needs to be drawn down, the gates are used.

Mr. Criss and Timothy R. Harwood, the Stillwater plant operator, figure out the optimal output from Stillwater based on engineering tables and water levels. The tables account for increased water pressure when the water level is higher, forcing more water through.

At the reservoir plant at the top of the reservoir's 40-foot dam, they hand-crank the gates to the appropriate opening.

AN 83-YEAR-OLD STRUCTURE

A dam was first put in at Stillwater in the 1890s, though "there may have been a smaller dam even before then," Mr. LaFave said.

It was increased to the current size in 1924. If the district needs replacement parts for any of the reservoirs, they usually have to be custom-made, using the broken part or a similar part to make a cast.

The state owns the dikes and dams that the district operates. The reservoirs and most of the land around them are not owned by the state or district. The district is responsible for the dams' safety.

During their rounds, Mr. Criss and Mr. Harwood measure water levels with piezometers, which look like tubes sticking out of the ground on the dike.

"We measure the elevation of the water inside the pipe with a water-sensitive probe," Mr. Harwood said.

Mr. Criss added, "We know the elevation of the top of the pipe and the water in the reservoir. The water in the pipe should be lower than the water in the reservoir."

The measuring indicates the strength of the earthen dike. "If precipitation has anything to do with these levels, that's a problem," Mr. Criss said. "It should be related to the reservoir."

UNIQUE IN NEW YORK

The regulating district is a public benefit corporation set up by legislative mandate. The Black River first had a regulating district in 1919. The Hudson River one was established in 1922 and they were combined in 1959. The Hudson River-Black River Regulating District now is the only one in the state.

The district is controlled by a board appointed by the governor. The seven board members serve five-year terms and come from different occupations. Three are from the Black River watershed, three are from the Hudson River watershed and one is an at-large member.

Each watershed has a separate budget, supported by fees paid by those who own "head" on the river. Head is the distance from the top of dams to the water below.

The district has 30 staff members divided between the two watersheds.

The district has no regulatory or enforcement jurisdiction.

Mr. LaFave became the executive director in 2005. He is from Dexter and has worked for the district since 2003, first as the Black River area administrator.

One of the district's primary purposes is communicating with those who depend on the river.

While the district's term for companies and towns that own head is "beneficiaries," Mr. LaFave prefers to think of them as partners.

"We're working together to do the best we can for all the people in New York state," he said. "We work hard to communicate."

That means talking to emergency response agencies when the rivers are high or when the agencies need the flow changed to help them flush a contaminant or find evidence.

"It's so important for the safety of people in our community," Lewis County Sheriff L. Michael Tabolt said. "We have emergency plans for every situation. We're an important part of their call list and they're an important part of ours."

Sheriff Tabolt served as the county's emergency manager from 1999 to 2003. He called the relationship with the district a partnership.

"When it's nice out, they're a silent partner," he said. "But we call on them during a need and when we do, they're always there for us."

A FRIEND TO BUSINESS

On a daily basis, the district communicates with businesses and power companies.

One business that relies on the Beaver River is the Croghan Island Mill Lumber Co. in Croghan. The mill is at least 150 years old.

The water from the river turns gears that power the mill's equipment. John W. Martin and his brother co-own the mill and handcraft furniture.

On a recent visit, Mr. Martin was making window casings.

"They're headed to New York City when they're done," he said.

When the water is high, as it was on April 25, the water meant to power the mill's gears can't flow out the other side. It won't provide the power.

But Mr. Martin knows that won't last long.

"It doesn't take long to get down if there's no rain," he said.

Power companies get daily updates from the district. Between the Hudson River and Black River watersheds, hydroelectric plants produce about 450 megawatts, or enough to power 450,000 homes.

To keep those plants running, the district gives power companies daily forecasts on the amount of water that should be coming down the Beaver and Black rivers.

"We understand each others' needs but also the limitations," Mr. LaFave said. "We don't tell them how to operate their hydro plant and they don't tell us how to operate our reservoir, but we communicate literally daily."

When he visits the Black River Power Plant, the Brookfield Power staff knows him by name.

That plant, on Route 3 east of Watertown, has three turbines from the 1920s that produce seven megawatts at full capacity — about enough electricity to power most of the homes in Watertown.

The Black River plant uses an ideal flow of 3,000 cubic feet per second. At 1,000 cfs, the flow is too low and the company must turn at least one of the turbines off.

"Water is our fuel," said Michael J. Zecher, superintendent for Brookfield Power. "The best part about it is it's clean, renewable, green energy."