Water Level and Flooding
Big Sandy is a reservoir fed by 420 square miles of watershed. 1 inch of rain in the watershed can cause several inches rise in Big Sandy lake elevation if the ground in the watershed is saturated or frozen, or if the outflow of water from the Libby Dam is restricted due to flooding in the Mississippi River.
It is not uncommon for Big Sandy water to rise above ordinary high water marks in the spring as snow melts in combination with spring rains. The trend chart below shows typical and maximum spring flooding levels on Big Sandy.
The Army Corps of Engineers manages Big Sandy water levels via the Libby Dam on the NW corner of the lake. Water is drawn down starting in October and then water rises approximately 2-6 feet each spring. This ACE report outlines the water level management plan.
Army Corps of Engineers web site provides up to the minute water level and trend data.
This Dam Profile Chart from the Army Corps of Engineers shows inflow, outflow and water levels managed.
The historical range chart at the Army Corps of Engineers web site shows the historical high and low water levels over time vs. time of year. Click the image above to see the current chart.