Sandbags sit stacked on top of each other along the St. Lawrence River Walk in May in Clayton. Lake Ontario water levels, which typically correlate with levels of the upper St. Lawrence River, have since declined below record breaking levels to 248.85 feet on Sunday. (Provided photo — Sydney Schaefer, Watertown Daily Times)

Lake Ontario water levels that have caused widespread flooding and shoreline damage are finally on the decline, albeit only by a couple of inches.

The elevation of the lake, which typically correlates with the elevation of the upper St. Lawrence River in the Thousand Islands, dropped below 249 feet on July 1 to 248.98 feet, and has steadily declined to 248.85 feet on Sunday. The International Lake Ontario-St. Lawrence River Board, which manages outflows from the lake, attributed the decline to recent warmer, drier weather throughout the Great Lakes, a shift from the cold, wet weather exhibited in the spring and early summer, and record-high outflows from the lake through the Robert Moses-Robert H. Saunders Power Dam in Massena and Cornwall, Ontario.

The board decided to raise outflows to a record-high 10,400 cubic meters per second, or enough water to fill 34,342 bathtubs per second, in mid-June after increasing them since the beginning of the month. It has maintained outflows at about that level since then.

It met Friday and decided to keep outflows at their current level, which is 200 cubic meters per second more than the limit for safe commercial navigation at current water levels as prescribed by Plan 2014, until lake levels drop another foot and fall below 247.7 feet, according to a news release. The board expects levels to drop by about 12 inches by mid-August.

Officials discussed whether they should raise outflows to the “maximum outflow capacity of the St. Lawrence River” over a series of incremental increases, among other possible strategies.

Raising outflows to maximum capacity, however, would require a shutdown of shipping on the St. Lawrence Seaway from Cape Vincent to St. Lambert, which would cause an estimated daily loss of $50 million in shipping, or $1.4 billion loss overall. Bruce Burrows, president of the Chamber of Marine Commerce, Ottawa, a binational organization focused on commercial maritime interests, also previously said hikes in outflows would further jeopardize shipping, and that if outflows remained at 10,400-cubic-meters-per-second for 10 weeks, the shipping industry would experience a $230 million to $290 million loss in revenue.

Other consequences of increasing outflows include additional flooding near Montreal and adverse effects for downstream property owners, recreational boaters, fish, wildlife and waterfowl habitats and breeding grounds, according to the board.

“Outflows at maximum system capacity for four weeks would hasten the recovery of Lake Ontario in the short-term; however, when compared to maintaining the current record high outflow strategy both options converge to within one inch by Dec. 31,” the board wrote in its news release. “This is because the amount of water that can be physically passed down the St. Lawrence River is directly related to the level of Lake Ontario. As the lake declines, so does maximum river capacity. Maintaining the current major deviation strategy will provide comparable benefit by the end of the calendar year, without creating $1.4 billion in economic damages.”

The St. Lawrence Seaway Development and Management corporations, entities that operate the Seaway on the U.S. and Canadian sides, respectively, issued speed and movement protocols last month in response to high outflows through the dam.

The protocols included speed controls and prohibitions of vessels meeting and passing in certain areas of the international waterway. They also directed mariners to operate “at the lowest safe speeds to minimize vessels’ wakes” and planned to station a tug boat at the Iroquois Lock, located in Canada across from the town of Waddington, in case vessel operators need assistance. Excessive precipitation across the Great Lakes Basin and high outflow from Lake Erie, which also experienced record-breaking water levels, were key factors in Lake Ontario and the upper St. Lawrence River experiencing unprecedented water elevations.

The effects were compounded by a heavy snow pack along the Ottawa River basin melting a little later than usual and major rains throughout the basin in late April and into May, which led to record flows from the river into the lower St. Lawrence River. This excess water caused Lake St. Louis, located where the Ottawa and St. Lawrence rivers meet, to exceed flood stage, flooding large areas near Montreal and elsewhere in Quebec. In order to mitigate the effects of this flooding, the river board reduced outflows through the Moses-Saunders dam, backing water up on Lake Ontario.