Assessment of potential implications of agricultural irrigation policy on surface water scarcity in Brazil

Abstract

Abstract. Expanding irrigated cropping areas is one of Brazil's strategies to increase agricultural production. This expansion is constrained by water policy goals to restrict water scarcity to acceptable levels. We therefore analysed the trade-off between levels of acceptable water scarcity and feasible expansion of irrigation. The appropriateness of water use in agricultural production was assessed in categories ranging from acceptable to very critical based on the river flow that is equalled or exceeded 95 % of the time (Q95) as an indicator for physical water availability. The crop water balance components were determined for 166 842 sub-catchments covering all of Brazil. The crops considered were cotton, rice, sugarcane, bean, cassava, corn, soybean and wheat, together accounting for 96 % of the harvested area of irrigated and rain-fed agriculture. On currently irrigated land irrigation must be discontinued on 54 % (2.3 Mha) for an acceptable water scarcity level, on 45 % (1.9 Mha) for a comfortable water scarcity level and on 35 % (1.5 Mha) for a worrying water scarcity level, in order to avoid critical water scarcity. An expansion of irrigated areas by irrigating all 45.6 Mha of the rain-fed area would strongly impact surface water resources, resulting in 26.0 Mha experiencing critical and very critical water scarcity. The results show in a spatially differentiated manner that potential future decisions regarding expanding irrigated cropping areas in Brazil must, while pursuing to intensify production practices, consider the likely regional effects on water scarcity levels, in order to reach sustainable agricultural production.

Significant baseflow reduction in the Sao Francisco River Basin

“…their needs poses a difficult task for decisionmakers. Because the Brazilian government has encouraged the expansion of irrigated agriculture to increase food production, we further expect increased water demand and conflict in the future of the SFB [75].…”

Significant baseflow reduction in the Sao Francisco River Basin. Is it time to call for attention on groundwater withdrawals?

“…These multiple water demands make the SFR a socio-economically important region and balancing their needs poses a difficult task for decisionmakers. Because the Brazilian government has encouraged the expansion of irrigated agriculture to increase food production, we further expect increased water demand and conflict in the future of the SFB (Multsch et al, 2020).…”

Drought intensification in Brazilian catchments: implications for water and land management

“…The Central region of the country, known for intense agriculture activity, in contrast, is projected to experience the greater coupled water demand-drought impacts, which will likely affect Brazilian agricultural production, such as coffee, soybean, and sugarcane (Koh et al 2020). As highlighted by Multsch et al (2020), part of this region is already experiencing concerning conditions in terms of water scarcity given the higher water use for irrigation, that may even aggravate due to agricultural expansion plans. These circumstances, however, are not restricted to this Central region: approximately 70% of crops catchments (crop cover > 50%) are expected to show increased irrigation-based water demand and more severe droughts in the middle of the century (figure 2(h)).…”