how water from dam can be mesured
Answers
Answer:
Round dams can be measured by pacing the circumference of the bank at water level, then divide this distance by 3.142 (π) to calculate the diameter.
Answer:
Your dam may not be as deep as you think! After a few storms and flooding, and years of livestock and loose dry pasture, most dams accumulate a lot of silt and organic material in the base. Desilting dams and building silt traps may be a worthwhile investment.
Explanation:
Volume (V) in cubic metres (m3) = surface area in square metres (m2) x the maximum depth in metres (m) x 0.4
The 0.4 factor allows for the standard slope (3:1) of the internal walls of an excavated farm dam. For most farm dam sizes, this calculation will underestimate the water volme, but this provides some reserve.
For rectangular or square dams, pace (in metre steps) the length (L) and width (W) of the bank at the water surface. Surface area is L x W in square metres.
For example, for a dam with the water edge 60m long and 40m wide, and 5m depth:
V = 60 x 40 x 5 x 0.4 = 4800m3 = 4 800 000 litres
For round dams, pace the circumference (C) of the bank at water level. The equation to get the area (A) from a known circumference is: A = C2 / 4π, where π = 3.142 approximately.
For example, for a round dam with a circumference of 150m, and 6m depth:
V = 1502 x 6 x 0.4 / (4 x 3.142) = 4297m3 = 4 297 000 litresMenu
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Calculating farm dam (excavated earth tanks) water volume
Page last updated: Friday, 31 July 2020 - 3:34pm
By following this guide, you can estimate the amount of water stored in a dam, and how evaporation and water for livestock, spraying and other uses will affect water reserves. This guide suits farm dams up to about 10 000 cubic metres. This page does not cover large gully-wall dams. Larger dams need designing by a registered engineer.
The Department of Primary Industries and Regional Development recommends you estimate dam volumes at the beginning of summer, and budget water supplies for the critical periods.
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Measuring the dimensions of your dam
Your dam may not be as deep as you think! After a few storms and flooding, and years of livestock and loose dry pasture, most dams accumulate a lot of silt and organic material in the base. Desilting dams and building silt traps may be a worthwhile investment.
With a few tools and some preparation, the method below gives a useful estimate of dam volume. It can be difficult to measure the dimensions of dams in use (unless empty), and calculated volumes are approximate. For water budgeting, always assume the usable volume is 10% less than the calculated volume, and allow for evaporation and difficulty of pumping or using the last 0.5 metre (m) of water in the dam.
At a minimum, you need to know the surface area of water in the dam and the maximum depth of water. For more accurate estimates of volume, you also need to measure the dam floor.
Simple, rough estimate of current water volume
Volume (V) in cubic metres (m3) = surface area in square metres (m2) x the maximum depth in metres (m) x 0.4
The 0.4 factor allows for the standard slope (3:1) of the internal walls of an excavated farm dam. For most farm dam sizes, this calculation will underestimate the water volme, but this provides some reserve.
For rectangular or square dams, pace (in metre steps) the length (L) and width (W) of the bank at the water surface. Surface area is L x W in square metres.
For example, for a dam with the water edge 60m long and 40m wide, and 5m depth:
V = 60 x 40 x 5 x 0.4 = 4800m3 = 4 800 000 litres
For round dams, pace the circumference (C) of the bank at water level. The equation to get the area (A) from a known circumference is: A = C2 / 4π, where π = 3.142 approximately.
For example, for a round dam with a circumference of 150m, and 6m depth:
V = 1502 x 6 x 0.4 / (4 x 3.142) = 4297m3 = 4 297 000 litres
Measuring the depth of water in a dam
One way is to use a 'dam dipper' as in Figure 1. This needs 2 people to hold a string across the middle of the dam, with a weighted string attached at about the mid-point. The weighted string should be longer than the full depth of water, and have coloured markers tied to it at set distances so the depth can be seen from the side of the dam. Allow the weight at the end of the string to rest on the dam floor.
On large dams, it may be easier to launch a canoe and measure from the canoe.
Line drawing of a simple system to measure the depth of water in a farm dam