Assessing agro-environmental sustainability of intensive agricultural systems

Sustainable production in water-scarce regions entails not to overshoot the sustainable blue water availability (BWA), which in turn requires addressing environmental flow requirements (EFRs). We explored the long-term effects of agricultural development, before (1984-1997) and during (1998-2018) the operation of the modern irrigation and drainage network of Tajan (TIDN), northern Iran, on the sustainability of blue water consumptions. A combination of different methods were applied to estimate hydrological EFRs of rivers, ab-bandans (traditional water reservoirs), and groundwater resources. Three major pollutants in the region's water resources, including nitrogen, phosphorus, and salinity, were used to estimate water quality EFR. Monthly agriculture water footprints (WFs) were calculated using the AquaCrop model, and then were compared with the region's BWA, which was calculated by subtracting monthly EFRs from monthly natural runoff. When WF exceeded BWA, the production system includes unsustainable water consumption. The EFR satisfaction of surface water decreased after TIDN operation by about 19%. Unmanaged nitrogen application and post-TIDN overexploitation of groundwater resulted in substantial increase in groundwater EFR violation. The TIDN led to more water consuming cropping pattern resulting in increased agricultural water consumption by about 73%. Overall, agricultural development in TIDN was beyond the capacity of the area, which resulted in up to about 167 MCM y^-1 unsustainable blue water consumption. Based on the results, the new framework presented for assessing agro-environmental sustainability could assist managers and policy makers to modify agricultural systems according to environment resilience.