Theory
Main formula for watering: source
(Eto x PF x SF x 0.62 ) / IE = Gallons of Water per day
where:
Eto: Get this from http://www.rainmaster.com/historicET.aspx
PF: This is the plant factor. Different plants need different amounts of water. Use a value of 1.0 for lawn. For water loving shrubs use .80, for average water use shrubs use 0.5, for low water use shrubs use 0.3.
SF: This is the area to be irrigated in square feet. So for a 30 foot x 50 foot lawn you would use 1500.
0.62: A constant value used for conversion.
IE: Irrigation efficiency. Some irrigation water never gets used by the plant, this value compensates for that. I suggest using 0.75 as the value for this. Very well designed sprinkler systems with little run-off that using efficent sprinklers can have efficiencies of 80% (use 0.80). Drip irrigation systems typically have efficiencies of 90% (use 0.90).
Installation
npm install watering
Usage
Make sure you change the values in config/development.json first.
watering
.calculate()
.then(function(data){
// watering volume and time
})
.catch(function(err){
// handle errors
})