Farmer Brown and his irrigation board have not woken up to the fact that Canada
ID: 117024 • Letter: F
Question
Farmer Brown and his irrigation board have not woken up to the fact that Canada went metric, so he needs your help to do some conversions for his irrigation. He plans to build a small reservoir to hold just enough water so that he can irrigate his 5 acre field, to a depth of 1.5 inches every week. What minimum capacity of reservoir will he need (assuming he emties the reservoir for each application), and what is the minimum pumping capacity he'll need to re-fill it in 6 days? He needs the answer in imperial units (acre.ft and cubic feet per sec (cfs)) and metric units (cubic metres and cubic metres per sec (cumecs)). Assume that 1 inch=25.4mm, 1acre=0.4ha, and 1ft=0.3048m.
Explanation / Answer
Volume required for irrigation 5 acre field, to a depth of 1.5 inches every week= (5x4046.86) x (1.5x0.0254) {as 1 acre = 4046.86 m2 and 1 inch = 0.0254m}
Volume required for irrigation 5 acre field, to a depth of 1.5 inches every week= 20234.3 x 0.0381= 770.926m3
Minimum capacity of reservoir that he will be needing= 770.926m3
The minimum pumping capacity he'll need to re-fill it in 6 days = (770.926/60)m3/day
The minimum pumping capacity he'll need to re-fill it in 6 days =128.48m3/day = 128/24*60*60 =0.00148703704m3/sec {As 1 day=24*60*60seconds, hence divinding by it.}
Minimum capacity of reservoir that he will be needing= 770.926m3 = 770.926 x 0.000810714acre.ft = 0.62445acre.ft
The minimum pumping capacity he'll need to re-fill it in 6 days = 0.00148703704m3/sec= 0.00148703704 x 35.3147cubic feet per sec
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