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.