Modeling of Hydrosalinity Balance within Kalaat El Andalous Irrigated District (Tunisia) using CIRFLE Model

Throughout (2005-2010) period, the most important water balance value (+3.64 million m3) was recorded during (2008/2009) campaign characterized by an intense rainfall (700 mm). While the lowest one (-0.77 million m3) was recorded throughout (2007/2008) campaign though it rainfall was only 333.5 mm. Analysis of monthly water balance indicates generally farmers tendency to over-irrigation. Annual salts balance recorded during (1997-2011) period indicates a general tendency of the study area to desalination (average annual salts balance is about -37928.7 tons). Modeling of hydrosaline balance using CIRFLE model indicates that drainage water volume showed a linear variation with irrigation water volume and rainfall amount variations with dominance of rainfall effects by comparison to irrigation water volume ones. In fact, for the same variation index (+20 %) of irrigation water volume and rainfall amount it was found that drainage water volume has increased by 10 % and 25 % respectively. However, CIRFLE simulations have shown that drainage water salinity variation is inversely proportional to irrigation water volume and rainfall amount variations. Thus, any increase of irrigation water volume and rainfall amount causes a decrease of drainage water salinity and vice versa with dominance of rainfall amount effects. On the other hand, it is noted that drainage water salinity is linear with that of irrigation water salinity. Furthermore, simulations have shown that evacuated salts amounts by drainage is proportional to irrigation water salinity, irrigation water volume and rainfall amount variations. Thus, it was found that rainfall effects dominate those of irrigation water volume whose dominate the effects of irrigation water salinity. Therefore, for the same variation index (+20 %), increases of evacuated salts amounts by drainage of 20 %, 16 % and 8 % were recorded respectively with rainfall amount, irrigation water volume and irrigation water salinity increases.