Pond-Free 102 Chapter 4
Calculating Reservoir Volume Required
Once you have decided on the design of the Pond-free feature you will be building, whether you decide to backfill with gravel or use Water Matrices, you will be digging the reservoir the same way. You’ll first need to know the amount of water needed to fill the stream and falls to get the feature running. Since you’ll be digging a hole that’s measured in feet, use the calculation below to find the cubic feet of water rather than the gallons needed. Estimate the average length and average width of the stream and falls in feet, and multiply by an average depth of 3”, one quarter of a foot:
Average LENGTH in feet x Average WIDTH in feet x 0.25’ (DEPTH) = Volume of Stream
You want to have at least three times as much water in the reservoir as you need to fill the stream, so when the pump is started, the level in the reservoir will only drop one third before the stream fills and starts returning water back into the reservoir. (With tall pumps you probably want to only lose one quarter of the depth before cycling.) Multiply the Dynamic Volume by 3 minimum (or 4 for tall pumps) to get the minimum Reservoir Water Volume in cubic feet:
Stream Volume x 3 (or 4) = Minimum Reservoir Volume (in cubic feet)
If you’re using Water Matrices, you’ll be digging a hole that holds the Reservoir Volume. If you want to backfill with gravel, you’ll have to triple the size of the hole!
Once you have decided on the design of the Pond-free feature you will be building, whether you decide to backfill with gravel or use Water Matrices, you will be digging the reservoir the same way. You’ll first need to know the amount of water needed to fill the stream and falls to get the feature running. Since you’ll be digging a hole that’s measured in feet, use the calculation below to find the cubic feet of water rather than the gallons needed. Estimate the average length and average width of the stream and falls in feet, and multiply by an average depth of 3”, one quarter of a foot:
Average LENGTH in feet x Average WIDTH in feet x 0.25’ (DEPTH) = Volume of Stream
You want to have at least three times as much water in the reservoir as you need to fill the stream, so when the pump is started, the level in the reservoir will only drop one third before the stream fills and starts returning water back into the reservoir. (With tall pumps you probably want to only lose one quarter of the depth before cycling.) Multiply the Dynamic Volume by 3 minimum (or 4 for tall pumps) to get the minimum Reservoir Water Volume in cubic feet:
Stream Volume x 3 (or 4) = Minimum Reservoir Volume (in cubic feet)
If you’re using Water Matrices, you’ll be digging a hole that holds the Reservoir Volume. If you want to backfill with gravel, you’ll have to triple the size of the hole!
