Rule Curve
Reviewed • Standard Hydrology Definition • WaterLakeLevel
# Rule Curve
A rule curve (also called a guide curve) is a published graphical and mathematical target schedule that dictates what elevation a reservoir should maintain on every day of the calendar year.
A rule curve balances conflicting seasonal priorities:
- In spring, the curve directs the dam to capture inflows to refill the basin for summer boating and municipal drinking water.
- In autumn, the curve mandates releases to lower the water surface, guaranteeing adequate flood control space before winter blizzards or spring deluges arrive.
You can inspect official rule curves using our Pool Schedule Checker.
A seasonal target elevation schedule established by dam engineers to guide reservoir storage decisions.
What Is a Reservoir Rule Curve?
A rule curve (also called a guide curve) is a published graphical and mathematical target schedule that dictates what elevation a reservoir should maintain on every day of the calendar year.
Balancing Competing Demands
A rule curve balances conflicting seasonal priorities:
- In spring, the curve directs the dam to capture inflows to refill the basin for summer boating and municipal drinking water.
- In autumn, the curve mandates releases to lower the water surface, guaranteeing adequate flood control space before winter blizzards or spring deluges arrive.
You can inspect official rule curves using our Pool Schedule Checker.
Explore Other Hydrology & Boating Terms
Acre-Foot
A volumetric water unit representing the amount of water required to cover one acre of land to a depth of one foot.
Conservation Pool
The volume of water stored in a reservoir dedicated to beneficial uses such as drinking water, power, and recreation.
Datum
A reference surface or mathematical baseline from which vertical elevations or geographic coordinates are reckoned.
Dead Pool
The critical low-water elevation below which water cannot flow downstream through gravity outlets.
Drawdown
The deliberate or natural reduction of a lake or reservoir water surface elevation.
Evaporation Loss
The invisible volumetric loss of water from a lake surface into the atmosphere caused by heat, sun, and dry winds.