Grain Guide 2018

Diameter in metres Depth in metres 1,2 m 1,5 m 1,8 m 2,1 m 2,4 m 3 8 600 10 760 12 900 15 000 17 200 3,6 12 200 15 300 18 300 21 800 24 400 4,2 16 650 20 800 25 000 29 200 33 300 4,8 21 700 27 200 32 600 37 900 43 400 6 34 000 42 500 51 000 59 400 68 000 7,5 53 000 66 000 75 600 92 700 108 000 9 76 500 95 500 114 700 134 000 150 200 10,5 104 000 130 000 155 800 182 000 207 900 12 126 000 170 000 203 500 237 000 271 000 13,5 172 000 241 000 257 500 300 000 344 000 15 212 000 266 000 318 200 372 000 425 000 16,5 257 000 321 000 385 000 450 000 514 000 18 306 000 382 000 458 000 534 000 610 000 ESTIMATED CAPACITY OF RESERVOIRS (IN LITRES) Example: 1 500 (m 2 ) x 5 (m) x 0,4 = 3 000 m 3 To calculate the capacity of your dam in mega litres (ML), divide the volume in m 3 by 1 000 e.g. 3 000 m 3 / 1 000 = 3 ML Gully dams You can estimate the capacity of small gully storages using this formula: Example: Water level height up bank = 2 m Length = 20 m, width = 10 m Volume of excavation = 100 m 3 Volume = (2 x 20 x 10 + 100)/5 = 100 m 3 Width and depth are measured at the embankment site and length is the distance water will back-up (you will need to add the volume of any excavations made below water level to give the total storage capacity). If the excavation volume is not known, substitute the depth of water at the deepest point as an approximation for the depth. Depth One way to determine dam depth is to row out into the dam and lower a weighted line over the side. When the line is vertical, measure the length of the line needed to reach the bottom. Alternatively, use a pole with distances marked on it. You will need to do this at a number of places across the dam to find the deepest point. An alternative for smaller dams, or if no boat is available, use a fishing line with a sinker on the bottom with a float attached. The line is cast out repeatedly, with the float gradually adjusted until it’s not quite floating on the surface. The distance between the float and the sinker will be the depth at that point in the dam. Again, you will need to do this at a number of places across the dam. Reference: Rob Dimsey. December 2006. Vegetable-matters-of-fact , Number 43 Volume = (width x maximum depth x length) / 5 (where 5 is the correction factor) 7 Conversion tables and formulae 8 GRAIN GUIDE 2018 Relevant