2000 m3 Irrigation Water Storage Tank: Sizing for the Peak, Not the Average An irrigation tank is not sized by how much water the farm uses; it is sized by how much it needs in the worst week, and by how fast the supply can put it back. A 2,000 cubic metre tank serving a peak daily demand of 300 cubic metres holds less than seven days - comfortable in a normal season and uncomfortably thin in a heatwave, when demand peaks and the source is at its lowest at the same time. The