The Ausable-Bayfield Conservation Authority has issued a Level One Low Water Advisory for the entire watershed.
Officials blame the effects of a winter with little snow.
The ABCA says stream flows in April were only 10 to 15 per-cent of normal which is a record low.
The Level One low water advisory is also due to the very dry winter followed by warm weather in March and part of April.
Authority officials say just 20 to 40 millimetres of rain fell last month paired with very little snow-melt.
The rainfall is less than half what's expected in the early spring.
Water levels this spring are the lowest recorded since 1946.
The ABCA advises residents and farmers to voluntarily cut water use by 10 per-cent for the duration of the advisory period.