United States Drought Monitor (USDM)

United States Drought Monitor (USDM) is used to describe drought conditions in a region.

Categories:

(1) abnormally dry (D0)

(2) moderate drought (D1)

(3) severe drought (D2)

(4) extreme drought (D3)

(5) exceptional drought (D4)

Parameters:

(1) impact on agriculture

(2) status of water supplies

(3) responses taken

Categories	Impact	Water Supplies	Response
abnormally dry	slowing of planting	variable	none
moderate drought	some damage to crops and pastures	streams and rivers low; wells low; reservoirs below normal	voluntary water restriction
severe drought	crop and pasture losses	moderate depletion	water restrictions imposed
extreme drought	major crop and pasture losses	severe depletion	widespread restrictions
exceptional drought	widespread crop and pasture losses	streams and rivers dry; reservoirs and wells extremely depleted	water emergency

Categories	Palmer Drought Severity Index	Standardized Precipitation Index
abnormally dry	-1.0 to -1.9	-0.5 to -0.7
moderate drought	-2.0 to -2.9	-0.8 to -1.2
severe drought	-3.0 to -3.9	-1.3 to -1.5
extreme drought	-4.0 to -4.9	-1.6 to -1.9
exceptional drought	<= -5.0	<= -2.0

Duration:

(1) short-term: < 6 months

(2) long-term: > 6 months

To read more or access our algorithms and calculators, please log in or register.