Evapotranspiration Estimates from Remote Sensing for Irrigation Water Management - Satellite-based Applications on Climate Change - page 201

Fig. 13.6 Distribution of monthly ET for each ORMVA
Using this monthly time series of spatially distributed ET, simple GIS analysis
produced statistics and charts for each of the three study areas. For example,
monthly mean ET by ORMVA (Fig. 13.6 ) shows Tadla with consistently higher
ET throughout the year, indicating higher quantity and more effective irrigation as
compared with Doukkala and Haouz. Also, the temporal distribution of ET act for
Tadla shows a later and more extended peak, sustained much later into the summer
than the other areas, which are known to have a more limited irrigation water
supply. For Doukkala, the primary growing season (indicated by peak ET act )is
relatively short, with 65-70% of the total annual ET act occurring during February
through May.
Annual ET maps for the period of study, Sept 2006-Aug 2007, are shown in
Fig. 13.7 for each of the three ORMVA study areas. An enlargement of the association
annour in the Tadla area is shown to illustrate the detail achieved for the ET maps.
Annual ET values greater than approximately 400mmare shown in the predominantly
irrigated areas. In the relatively well-watered Tadla ORMVA, the irrigated areas are
particularly pronounced with annual ET typically exceeding 800 mm.
13.6 Water Balance Analysis
13.6.1 Method
A simplified water balance analysis was conducted at the irrigation sector level for
each ORMVA on a monthly time step with surface and subsurface storage assumed