Water footprint of flooded rice cultivation in subtropical climate in extreme southern Brazil

Due to projections of world population growth, the concern with water resources is becoming increasingly urgent. Thus, the use of water contabilization indicators, such as the water footprint, can be useful in the pursuit of sustainability. Rice is one of the most consumed foods in the world, Brazil is the 9th biggest producer and the largest producer outside the Asian continent. The state of Rio Grande do Sul (RS), in Brazil, is responsible for about 70% of the national production. Since there is little information on the water footprint of rice cultivation in this state, this study aims to: quantify the rice yield through field experiments (2020/2021 and 2021/2022 harvest) in the municipality of Cachoeirinha- RS, measurement and segment the crop water requirement and the water footprint of flooded rice through remotely obtained meteorological data and presents a critical analysis on the accounting of the water footprint of this crop. On the mean of the two harvests, the water footprint was 443.0 m³ t− 1 (62.1% green water footprint and 37.9% blue water footprint). The crop water demand was 5763.3 m³ ha− 1. The yield was 13.010 t ha− 1. Under experimental conditions, the water footprint is in the optimal range of maximum technical and economic efficiency. The inclusion or not of return flow in accounting for the water footprint of flooded rice cultivation is a highly relevant inconsistency. Another inconsistency is the lack of isonomy in gray water footprint accounting because of the variable "maximum allowable concentration of the critical pollutant".