Crop water footprints with special focus on response formulation: the case of Gomti river basin (India)

Abstract

Increasing water scarcity places considerable importance on precise quantification of water consumption. The concepts of virtual water content (VWC) and water footprint (WF) are increasingly being used to analyse the water consumption and to support optimal crop and water management practices at different spatial scales. In the present study, the blue, green and grey VWC of crops and WF of crop production within the Gomti river basin (GRB) in India were assessed for irrigated and rainfed conditions. Total WF is the sum of blue, green and grey WFs within the basin. Blue WF is the amount of surface or groundwater used in crop evapotranspiration (ETc), green WF refers to amount of rain water use in ETc, and the grey water use is the volume of freshwater that is required to assimilate the agricultural pollutant load to acceptable levels. On the basis of variability in ETc, the GRB was divided into four spatial resolution units (SRUs). A linear programming model was developed to optimize the area under each crop in different SRUs with the objective function of minimizing the blue WF within the GRB. The findings show that annual WF of crop production within the GRB was 12,196 Mm3, of which 89% was from irrigated agriculture. Wheat, paddy and sugarcane shared 94% of the total WF of crop production within the basin. Share of blue and green WFs in total WF of the basin was 48 and 46%, respectively. There was considerable variation in VWC of crops in different SRUs. The VWC-based optimal allocation of crops would result in savings of 196 Mm3 in blue WF per year. Considering the large WF of crop production, optimizing the crop planting pattern is the key to achieve more sustainable water use within the basin. The approach suggested in this study will be useful in devising informed policy decisions related to crop choices and their cultivation areas so as to ensure efficient use of water resources