Figures 3(a-h) show the drought maps for each of the years studied, at a glance the comparison
within an entire area for a multi-temporal series it’s straightforward. In this case we can conclude
that 2005 image shows highest deficiencies in the provision of surface water and highest drought
values.
As mentioned above NDVIDEV and VCI indices make use of data collected from a multi-temporal
series, including the maximum, minimum and average. These parameters can vary greatly depending
on the size of the series. In the case of NDDI, the values obtained are independent of both the
size of the study area as of the time series. The maps shown in the Figure 3 correspond to an area of
132 km2
, however, if it is greater area, as shown in Figure 4(a), after performing the process and
select the same area will reach the same result. This is illustrated in Figure 4, which is a zone of
22500 km2
; the location of the study area is highlighted too.
The average of the indices shown in Figure 2 has been calculated for a small area, in which case
you may receive an approximate idea of changes that have each of the indices over the time series.
By taking a wider region, as shown in Figure 4(a), by plotting the averages of each year, his profile
would be flatter than the responses shown in Figure 2 which in turn may make it less easy to interpret
and analyze the effects of drought