Dimensions of Gypsum Bed in Relation to Residual Sodium Carbonate of Irrigation Water, Size of Gypsum Fragments and Flow Velocity

Relative importance of the factors like total salinity, sodium adsorption ratio (SAR), residual sodium carbonate (RSC) of the irrigation water, size of the gypsum fragments and flow velocity on the dissolution of gypsum placed in the irrigation channel was studied. Based on these factors, dimensions of a gypsum bed in the water course were calculated for the reclamation of sodic waters. The calculations showed only negligible effect of the electrolyte concentration and SAR of the irrigation water on the dimensions of the bed. A good agreement was found between the theoretically predicted and the experimentally determined solubility of gypsum using a bed of mixed size gypsum fragments. The RSC of water decreased from 5.75 to 0.75 m.e.l⁻¹ after passing water through the gypsum bed, CO₃⁻²+HCO₃⁻ concentration remained unchanged, showing no precipitation of CaCO₃ in the gypsum bed.