2. Hydrological analysis
There are four parameters in hydrological issue, surface water source, irrigated area, stream density in subwatershed,
and ground water yield and total dissolved solid. Surface water source was derived from 3 scenes of
Landsat TM acquired during December 2004-February 2005 and irrigated area data collected by the project sites of
the Royal Irrigation Department. Stream density was calculated from stream length within sub-watershed areas.
groundwater yield and total dissolved solid at a scale of 1:100,000 are available from the Department of Mineral
Resources. Those four parameters of hydrological data were categorized to drought severity class as illustrated in
Table 3 and Fig. 4.