Reference http://drought.unl.edu/DroughtBasics/TypesofDrought.aspx drought.unl.edu means different things different disciplinary perspectives four kinds of drought sub-categories human activity http://drought.unl.edu/DroughtBasics/TypesofDrought.aspx “agricultural droughts” http://drought.unl.edu/DroughtBasics/TypesofDrought.aspx “agricultural droughts”