Assessment of quality contributing parameters using hydrochemistry and hydrogeology for irrigation in intermontane Manipur valley in northeast India

Abstract

Agriculture contributes a major share to the domestic products and provides employment of ~ 22.13% of the total workers in the Manipur Valley which has a population of nearly 2 million. The irrigation index parameters like Sodium Absorption Ratio, % Na, Permeability Index, Kelly's Index, Magnesium Hazard, Residual Sodium Carbonate and Base Exchange of groundwater in MV have been evaluated. SAR values indicate that 22% of the total samples are found unsuitable in which 19% belongs to piedmont groundwater. % Na shows that 12% of the total sample representing Piedmont Zone is unsuitable. PI indicates that 41% of samples fall into category III in Doneen's diagram representing bad quality. KI shows that 34% of samples are unsuitable in which Piedmont Zone, Alluvial Plain and Flood Plain shares 22%, 9%, and 3% of total samples respectively. MH reveals that 50% of samples have > 50% MH which causes detrimental effects on the agricultural yield. RSC shows that 28% of samples are unsuitable where most of the samples are from PZ. The expanded Durov indicates that groundwater is dominated by Ca-Mg-Cl-HCO3 facies suggesting initial and intermediate stages of chemical evolution under ion mixing process. The hydrogeologic section implies that the initial stage of evolution takes place in PZ while intermediate stage undergo in AP and FP. The unsuitable groundwater in PZ is due to encrustation of gypsum, halite and evaporates in Disang shales. Thus, the evaluation of common irrigation indices is found useful in assessing the groundwater quality for irrigation in Manipur valley.