Blaney Rainfall Thiessen Area

The South Florida Water Management District uses a modified Blaney-Criddle equation to determine evapotranspiration. This polygon feature class defines the location and extent of areas associated with rainfall monitoring sites used to calculate net depth of application area Districtwide. The 'Modified Blaney-Criddle' is a variation of Blaney Criddle, which multiplies the ET from Blaney-Criddle by a coefficient that relates mean air temperature to the growth stage of a crop. Additionally, effective rainfall is calculated using the mean temperature and hours of daylight, the Blaney-Criddle ET, average monthly rainfall and soil factor. Further calculations consider average rainfall to drought rainfall (1-in-10 year drought). The difference between monthly drought effective rainfall and monthly ET becomes the basis for water allocations.