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An Interactive Calculator For Drip Irrigation The drip calculator helps you to choose the correct depth to place the FullStops for drip irrigation. It can help you to work out why a FullStop may rarely respond to drip irrigation, or why it may respond all the time. Below are the instructions on how to use the calculator for drip irrigation. At the bottom of this page is the link to download the calculator. The drip calculator is set up differently to the sprinkler calculator. You only have to fill in two boxes in the centre column; the Emitter Application Rate (l/h) and the Duration of Irrigation (h). The default values are 2 l/h emitter and 5 hour duration irrigation. The emitter application rate multiplied by the duration of irrigation gives the amount of water, in litres, coming from one emitter. The amount of water applied in mm or Ml/ha depends on the spacing between irrigation laterals and the distance between emitters on each lateral. Place the Distance between Laterals (in m) and Emitter Spacing along Lateral (in m) for your layout in the boxes on the left. The grey box on the right allows you to set the soil water conditions before irrigation. Click the moist button if the irrigation interval is frequent or the dry or very dry buttons if the soil is allowed to dry out between irrigations. Two contrasting soil profiles are shown in cross section from 0 to 1000 mm depth. The soil on the left has wide wetting patterns, so the water does not penetrate very deep. The soil on the right has narrow wetting patterns, so the water penetrates much deeper. Most soils fall between these two extremes. By varying the duration of irrigation, the calculator will show how deep water might be going, and the total mm of water applied. This will help to choose appropriate depths for the FullStops. If you know roughly how many mm of water you want to apply each week it will also help you to work out the appropriate irrigation interval. You will note that the type of soil has a much greater impact on the depth of wetting than whether the soil was moist or dry before irrigation. Note that a given amount of water goes a lot deeper under drip than sprinkler irrigation. This is why we recommend that the FullStop be placed deeper under drip than sprinkler irrigation. The data for this simulation comes from the model WETUP (see http://www.clw.csiro.au/products/wetup/link for more details).These simulations are for one drip emitter only. If the wetting patterns from adjacent drippers join up, the patterns would be a bit different.
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