2 

index (WEWI) according to the given principles. However, this evaluation is subjective, 
and human error may affect the results when using trial and error to adjust the weights of 
the major and minor factors in the WEWI. The effectiveness of this system’s warnings 
has been doubted, because its early warning ability and warning risk cannot be explored, 
and thus related organizations have had a hard time using the information that the WEWI 
provided. 

The difference between early warning systems and monitoring systems is that the 

former should explore the uncertainty of future hydrologic conditions, and evaluate water 
shortage situations caused by hydrologic processes in a specific water supply district 
during a specific period. With regard to reservoir water supply systems, if it is known that 
a severe water shortage will occur in the future, then to fulfill the water demand during 
the operation period, early water-limiting measures may be used to avoid a disastrous 
water shortage before the next wet season arrives. Common sense seems to indicate the 
importance of system establishment pre-processing, but the empirical support is still 
lacked. Recent studies that have attempted to establish a direct relationship have not been 
very successful. The study review the suitability of “Regional Water Resources 
Regulations” according to the mechanism of established model that build up with the 
selected factors. The result of this study could be useful to water resources manager 
responsible for planning a water resources drought early warning system in local 
conditions. 

Keywords: Drought, Drought early warning, Drought early warning index, Water 

shortage rate, Regional water resources regulations. 

 

 

 

(Wilhite et al., 

2007)

(Vlachos and James, 1983)

 

(Palmer Drought 

Severity Index, PDSI)

(Stan-

dardized Precipitation Index, SPI)

(Total 

Water Deficit, TWD)

(Days of 

Supply Remaining, DSR)

(Surface 

Water Supply Index, SWSI)
(Reclamation Drought Index, RDI)(Hayes, 2006; 
Heim, 2002; Keyantash and Dracup, 2002; Wilhite, 
2005)

Wilhite and Glants (1985)USISDR (International 
Strategy for Disaster Reduction, 2007)

Iglesias 

(2009)

(Meteorological drought)