WATERTOWN, N.Y. (WWTI) — Drought conditions along the Great Lakes and St. Lawrence River have prompted officials to make changes in outflow levels.

On Friday, the International Lake Ontario- St. Lawrence River Board announced that it would implement deviations to the plan-prescribed “Rule Curve” flows.

The Board stated that in accordance with the International Joint Commission Directive on deviations, the regulation plan that directs water levels needs to be followed until water levels reach any of the defined triggers.

However, due to water levels decreasing below the “low threshold,” outflows are set to be decreased.

This is due to abnormally dry to moderate drought conditions within the Great Lakes- St. Lawrence River watershed. Based on data from the GLERL Hydromet databases and U.S. Army Corps of Engineers data, the past 12 months over Lake Ontario have been the driest since 1966.

The Board reported that as a result, the water level in lake Ontario rose 2 centimeter, or 0.8 inches, in the month of May. This is compared to the average rise of 9 centimeters, or 3.6 inches, May typically logs.

A map of the drought monitor for North American in April is pictured below.

Map: National Centers for Environmental Information, National Oceanic and Atmospheric Administration

United States Co-Chair of the International Lake Ontario- St. Lawrence River Board Stephen Durrett stated “the level of Lake Ontario has declined below the low Criterion H14 threshold specified in the IJC regulation plan.”

Deviations from plan-prescribed “Rule Curve” flows under the low Criterion H14 threshold are meant to “provide all possible relief to municipal water intakes, navigation and power purposes, upstream and downstream.”

Regarding deviations, on May 29, outflows from Lake Ontario were set to 100 cubic meters per second below the amount perscribed by the “Rule Curve” of the regulation plan.

On June 5, outflows were further decreased to 7,620 cubic meters per second, which is 200 cubic meters per second below the amount prescribed by the regulation plan.

The International Lake Ontario- St. Lawrence River Board stated that it will continue to monitor conditions and the effects of the deviation strategy, while also tracking weather forecasts and drought conditions.