**4.5 HDI1 in Sutami watershed**

The threshold analysis for the Sutami sub-watershed using observational data from 1991 to 2006 showed the value for Q50 was 64.34 m3 /sec and Q80 was 40.03 m<sup>3</sup> /sec. Meanwhile, HDI1 for Q80 was calculated to be 0.00 while the limit at Q50 was 0.0119 and at 70% Q80 was �0.0059.

The calculation showed that HDI1 ranged from 0.000 to 0.007 while HDI2 was from 0.000 to 0.007 in line with the severe drought criteria and this means the simulation was unable to determine the exact time the drought starts and ends. Moreover, the dry deficit duration calculation showed that the simulation data was accepted at α = 5% while the median test indicated that the simulation data have the same characteristics and are not significantly different from the observation data. The "scatterplot" test of the simulation data presented in **Figure 9** and the Flow Duration Curve test in **Figure 10** also showed that there was a match between the observation and simulation data.

**Figure 9.** *The suitability analysis of the simulated scatterplot in Sutami dam [21].*

**Figure 10.**

*Flow duration curve conformity analysis of the simulation results at Sutami dam [21].*


**Table 1.**

*Results of the Z-test QObservation and QSimulation in Sutami dam [21].*
