## Just-A-Falls Calculations

##### Calculate how many gallons of water are in a Just-A-Falls reservoir:

**For Reservoir filled with 3″ -6″ sized stone:**

Length x Width x Average depth x 7.48 x 0.40 = Total gallons.

*60% of the reservoir is mass / rock and 40% is water. This formula assumes 3″ -6″ size stone is used. Smaller stone will decrease the amount of water in a reservoir.*

**For Reservoir filled with Res-Cubes:**

Length x Width x Average depth x 7.48 x 0.85 = Total gallons.

*10-15% of the reservoir is mass / rock and 85% – 90% is water.*

##### Calculate how many inches of draw down there will be in a Just-A-Falls reservoir to fill the stream:

Total gallons contained in reservoir / Depth of reservoir in inches = gallons per inch.

*Calculate how many gallons of water your stream requires using the stream formula. Try to have three times as much water in your reservoir than you will have in transition.*

Total gallons required for the stream / Gallons per inch in reservoir = Total inches the water level will be drawn down in reservoir.

*Make sure that there will be enough water remaining in your reservoir to keep the pump completely submersed in water. This is required so that the pump will cool properly.*