There are several USGS gages on the Penobscot River.
• East Branch Penobscot (Grindstone):
• West Enfield
• Eddington
• Bangor

In additional, the National Weather Services’ “Advanced Hydrological Prediction” Services provides the following forecasts:
• East Branch Penobscot (Grindstone)
• West Enfield
• Eddington
• Bangor

Correlations
The USGS gauge at Eddington provides the best guidance for those paddling the stretch of the river between Old Town and Brewer, which has the most difficult rapids:
• Less than 3′: Low water. Rapids may be scratchy, but are less likely to swamp open boats. Careful route finding may be necessary.
• 3 to 7 feet: Medium Water: Best flows for clean lines, but may be challenging for loaded boat. Canoes should be outfitted with flotation. Portaging may be appropriate, especially early season.
• Greater than 7 feet: High water. Long swims possible.