Weatherwise Watering

Because Weatherwise forecasts are the best that you can get. Our forecasts are not the cheap or free ones that are available from overseas sources that don’t know about Australian conditions. We purchase our forecasts from the Australian Bureau of Meteorology (BoM) . The BoM run multiple forecast models using super computers, and teams of meteorologists refine the results using their extensive knowledge of local conditions. They produce forecasts for over 400,000 points on a grid extending right across Australia. You’ll never be more than 3 km from the most accurate forecast in the country.

As an added bonus, if you're using water for a domestic garden (tick the box when subscribing), then you will receive our Weatherwise irrigation recommendations for the coming week.

SWAN Systems is a cloud-based decision support system for irrigators. The software analyses weather, irrigation, soil moisture, and fertiliser application data to provide recommendations for optimised irrigation – it takes the guesswork out of optimising water use. It also provides integrated modules for nutrient planning and management, and satellite data is used to generate a health (or “greenness”) index for sites based on absorption and reflectance data.

For more information, visit our SWAN Systems website .

We'll quote the Australian Bureau of Meteorology (BoM) here, "Evapotranspiration is the term used to describe the part of the water cycle which removes liquid water from an area with vegetation and into the atmosphere by the processes of both transpiration and evaporation." If you are interested, the BoM goes into more detail here .

The amount of water extracted by vegetation will depend on the land use, e.g. the amount of water extracted by a football oval covered in grass will differ from the amount used by a vineyard. Another factor is the crop stage; typically larger more mature crops will extract more water than young crops.

It would be impractical to forecast and publish evapotranspiration for a wide variety of crops so in most contexts "reference evapotranspiration" or ETo - the amount of evapotranspiration over a crop of green grass about 12cm (5in) high - is used and a "crop factor" is applied to adjust ETo for different crop types, growth stages and seasonal variation.

NOTES:

• This procedure is only applicable for domestic gardens; use in other contexts could lead to crop/field damage and/or financial loss. Consider our full SWAN Systems service for non-domestic situations.
• A prerequisite to use this method is that you must have a controller that lets you set your irrigation as a percentage of a pre-set "normal" amount.
• Weatherwise's recommendations are calibrated for lawn. Other parts of your garden will have different watering needs depending on plant type, soil type and so on, so you may have to adjust the amount supplied through the sprinklers/drips to those parts until you get it right through trial and error.

Procedure:

1. Set up your reticulation system and run times so that the irrigation controller's 100% irrigation will supply the maximum amount of water that your garden would need for the hottest week of the year. Your welcome email contains our Weatherwise estimate of that amount. The amount that you need to apply at each application will depend on your watering schedule, the following table is a guide.

   Maximum Weekly Irrigation (mm)	Watering Days Per Week
   	1	2	3	4	5	6	7
   20	20	10	7	5	4	3	3
   25	25	13	8	6	5	4	4
   30	30	15	10	8	6	5	4
   35	35	18	12	9	7	6	5
   40	40	20	13	10	8	7	6
   45	45	23	15	11	9	8	6
   50	50	25	17	13	10	8	7
   55	55	28	18	14	11	9	8
   60	60	30	20	15	12	10	9
   65	65	33	22	16	13	11	9
   70	70	35	23	18	14	12	10

2. Choose one day a week to be your irrigation planning day. For example, if you water in the early morning on Tuesdays and Saturdays, you might set Monday as your planning day so that you can set the controller Monday evening in time for the next day's irrigation.
3. On your planning day, check your inbox for your Weatherwise forecast and find the irrigation recommendation which is expressed as a percentage.
4. Alter your controller's percentage setting to conform with the Weatherwise recommendation. When the forecast for the week is hot to very hot, Weatherwise will recommend 100% or close to, for cooler weeks, the recommendation will be less.
5. If your garden is under cover and there is significant rainfall predicted, Weatherwise will issue an additional recommendation for under cover gardens.
6. Weatherwise watering can't take into account the particular circumstances of each garden - the different plants, soil types and so on. Consequently, our irrigation recommendations may not be an exact fit for your garden. Therefore, you should review your garden's health periodically and if necessary, adjust your controller's run times that correspond to 100% up or down as appropriate.

Weatherwise's rainfall forecast comprises two items: a probability of rain and an expected range, but what exactly do they mean?

To mangle a well known quotation, "nothing in life is certain except death and taxes... and the rainfall forecast won't be right!" Of course weather forecasters know this very well so will often term their forecasts in terms of probability and chance and quote a range of possible rainfall figures. In this way, you will have more information to judge the likelihood of rainfall than you would have with a bald figure of Xmm rain.

For a much better explanation of this, visit this post from the Australian Bureau of Meteorology (BoM).