• To determine total gallons of water in a lagoon you first need to find 4 measurements:
(1) width of top of water,
(2) length of top of water,
(3) water depth, and
(4) slope of bank.
• To determine the slope of the bank; you use two tape measures and determine how much of a run is required to make a one foot drop. Most banks are 3:1 or three feet run for every foot drop.
TOW = Top of Water
BOW = Bottom of Water
AOW = Average of Water
Accurate Total Gallons = Average Square feet of Lagoon x Water Depth x 7.5
Top of Water Square Feet (TOWsf.) = TOW. of length x TOW of width
Bottom of Water Square Foot (BOW sf.) = (TOW length – total run) x (TOW width – total run)
Average Square Foot of Lagoon (AOWsf) = (TOWsf + BOWsf ) / 2
Total Run is determined from slope of bank. See example as follows:
Run of 3:1 slope = depth of water x 3 foot run for every foot drop x 2 banks
Run of 4:1 slope = depth of water x 4 foot run for every foot drop x 2 banks
Measurements = 300 length of top of water; 200 width of top of water; 15 water depth; 3:1 slope
Run = 3 x 15 x 2 = 90 feet
TOWsf = 300 x 200 = 60,000 sf
BOWsf = (300-90) x (200-90) = 210 x 110 = 23,100 sf
AOWsf = (TOWsf + BOWsf) / 2 = (60,000 + 23,100) / 2 = 83,100 / 2 = 41,500 sf
Gallons in Lagoon = 41,500 (AOW) x 15 (depth of lagoon) x 7.5 (gallons per ft3) = 4,668,750 gallons
Lagoon Pumping & Dredging, Inc.
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