Mayfield Reservoir

As of August 24, 2026, Mayfield Reservoir is filled to 97.3% of its total capacity, holding roughly 161 hm³ of water out of a maximum 165 hm³. At this level the reservoir is high.

Over the most recent week on record the fill level has held broadly steady (-0.2 pts), and it is 1.0 points above its level on the same date a year earlier.

Across the readings we hold for Mayfield Reservoir — 1424 data points between October 1, 2022 and August 24, 2026 — the level has ranged from a low of 88.8% (December 9, 2025) to a high of 99.5% (March 13, 2026). On average the reservoir is fullest around June and at its lowest around November.

It is operated by USGS primarily for multiple purposes. It lies within the Washington basin at 46.503°N, 122.588°W.