CARVALHO, J. J.; http://lattes.cnpq.br/6432289075200127; CARVALHO, Joaquim José de.
Resumo:
The main purpose of this research was to verify the effects of the temporal
and spatial variations in the water application time at the end of the field on the
performance of a furrow irrigation system from the Sao Goncalo irrigation district,
operated under cutback flow conditions. For quantifying the spatial and temporal
variations in the water application time, as a consequence of others variations in the field
and operational parameters, evaluations were performed in six furrows, chosen in a such
way to mostly embrace variations in the cross sectional side of the area, for each irrigation
event along the crop season. In these evaluations, the water depth required, the furrow
inflow and outflow, the advance phase, and the furrow cross sectional area were measured.
The infiltration opportunity time at the end of the field was estimated by the Kostiakov-
Lewis equation, which was derived, in real-time, from the fitting of the simulated advance
to the measured one, using the SIRTOM model. Also, the water application time was
determined in a real-time basis, given by the sum of the advance and opportunity times at
the end of the field. The SIRMOD model was used to forecast the performance of the
irrigation system, which was operated in a way to establish the adequate irrigation
condition. The results show a substantial effect of the water application time variations on
the performance of the furrow irrigation system. Along the time and space, the minimum
and maximum values of the application efficiency, of the runoff ratio and of the deep
percolation ratio were, respectively, 33.1 and 95.3%, 0 and 61.3%, and 0.1 and 66.4%.
These amplitudes generated maximum spatial variations along the crop season equal to
33.0, 162.0 and 140.5%, respectively, in the application efficiency, in the runoff ratio and
in the deep percolation ratio. Spatially, the temporal variations were 26.3, 78.4 and
233.3%. This study shows the importance of performing a spatial and temporal systematic
monitoring in the field parameter variations, so that to have an estimation of the irrigation
system performance the most representative as possible of the global field conditions.