Therefore, effective rain fall for April at the Perth metro station = 2.9 x 8.7 or 25.2mmĪverage evaporation over April is 133.4mm over 30 days. These events average 11.7mm, so 8.7mm when the first 3mm is subtracted. Over the past 25 years there has been an average of 2.9 days where rain greater than 3mm has fallen. The effective rainfall is subtracted from the monthly evaporation, then divided by the number of days per month to give effective daily evaporationĮxample: April at the Perth metro weather station. The average depth of effective rainfall is multiplied by the average number of days rainfall occurs to give effective monthly rainfall. ![]() In June, July and August, rain events greater than 2mm but not including the first 2 mm are considered effective.In April, May, September and October, rain events greater than 3 mm but not including the first 3 mm are considered effective.In January, February, March, November and December, rain events greater than 4 mm but not including the first 4 mm are considered effective.The following rules have been applied to rainfall when calculating effective daily evaporation. To select the most accurate data for your farm, first select the region and then the nearest station to you.Įffective daily evaporation takes into account the evaporation, rainfall and storage capacity of soil to estimate the water required in addition to rainfall, to supply crop demand. SILO is an enhanced climate database hosted by the Science Delivery Division of the Department of Science, Information Technology and Innovation (DSITI). Irrigation proportion or effective area of shade x Irrigation efficiency factorĮvaporation and rainfall has been calculated for each month using data for the past 25 years (1990 to 2014) from Scientific Information for Land Owners SILO weather data service. The following calculation is used to estimate water requirement:ĭaily water use =Average effective daily evaporation x Crop factor x How the Calculator estimates water requirement If you are a registered user, previous calculation will be saved and can be edited or reprinted. Previous calculations for your current session will be saved and can be edited or printed. A summary of the scenario including planting date, location, water required per area and hectare is displayed and able to be printed. See the heading Irrigation efficiency factor later in the Further info tab for more details A good irrigation efficiency is 1.1 (default). Irrigation efficiency refers to how evenly the water is being applied to an area. An explanation of irrigation proportion and effective area of shade is given later later in the Further info tab Irrigation proportion/Effective area of shade refers to the area being covered by irrigation or the canopy of the crop. Select the approximate planting date and start month of irrigation if different to planting.įor perennials there is no need to add a planting date.Īdd the Area planted in hectares. Coarse sand is most appropriate for the majority of the coarse sands of the Swan Coastal Plain.Ĭhoose a Crop you are growing in the Crop drop down tab.įor annual crops a Planting month and Started irrigation month tab will appear. Using the Soil type drop down tab, select either the Coarse sand or the Clay/Loam tab. Use the Open map to select location tab or select a region and then location using the drop down menu’s to find a weather station closest to your farm. washing produce, packing sheds and winery operations) should be calculated separately and considered when planning water needs. These activities as well as other farm uses of water (i.e. It does not take into account extra water required for frost control, preventing erosion and sandblasting, cooling a crop or applying nutrients through irrigation, in addition to watering requirement. The program calculates the crop water requirement to produce commercial crops. Allowance needs to be made for years that are hotter, drier, cooler or wetter. It should not be used for detailed farm irrigation scheduling.Īverage weather data has been used to calculate water requirement for crops. ![]() The Irrigation Calculator provides broad guidance for water budgeting on commonly grown commercial crops in Western Australia.
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