Lake level guides

The numbers on a lake page are only useful once you know what the pool lines mean and why the level moves. These three guides cover that: the vocabulary of pools and datums, who sets the level and how, and the autumn drawdown that catches first-time lake visitors out every year. Each is written from the operating agencies' own water control manuals and public data, and each links back to the live lake pages so you can see the ideas on a real gauge.

• Full pool vs flood pool: What the pool elevations on a lake page mean and how to read the gauge.
• How reservoirs are managed: Who decides the level, what the rule curve is, and why releases happen when they do.
• Lake drawdown schedules: Why lakes are lowered every autumn, how far, and how to tell a drawdown from a drought.

Looking for a specific lake instead? Start from the homepage search or the A to Z list.