receiving a first current moisture loss value;

determining a first net moisture loss value since a last irrigation start day utilizing the first current moisture loss value;

retrieving a threshold moisture loss value associated with one or more watering programs controlled according to a first irrigation control level of a plurality of selectable irrigation control levels where each level corresponds to a different way of associating threshold moisture loss values to watering programs;

defining a current day as an irrigation start day for the one or more watering programs associated with the first irrigation control level of the plurality of selectable irrigation control levels when the first net moisture loss value has a predetermined relationship with respect to the threshold moisture loss value;

identifying a first plurality of watering programs associated with an irrigation class of the first irrigation control level that is a class irrigation control level;

the defining the current day as the irrigation start day comprises authorizing the activation of the first plurality of watering programs associated with the class when it is determined that a class irrigation control option is to be activated based on the first net moisture loss value;

identifying a global irrigation control level;

determining a global last irrigation start day associated with the global irrigation control level;

the receiving the first current moisture loss value comprises receiving one or more current moisture loss values including the first current moisture loss value from one or more moisture loss sources;

identifying at least one of the one or more moisture loss sources to be used in determining a global net moisture loss value;

determining the global net moisture loss value based on moisture loss values received from the identified at least one of the one or more moisture loss sources received since the global last irrigation start day;

determining whether the global irrigation control level is to be activated based on the global net moisture loss value; and

authorizing activation of a second plurality of watering programs associated with the global irrigation control level when it is determined that the global irrigation control level is to be activated based on the global net moisture loss value;

wherein the second plurality of irrigation programs comprise all watering programs controlled based on threshold moisture loss values and not associated with the class irrigation control level or a program specific irrigation control level; and controlling the irrigation system.