Groundwater saving and quality improvement by reducing water footprints of crops to benchmarks levels

Abstract

a b s t r a c tThe formulation of water footprint (WF) benchmarks in crop production -i.e. identifying reference levels of reasonable amounts of water consumption and pollution per tonne of crop produced -has been suggested as a promising strategy to counter inefficient water use and pollution. The current study is the first to show how setting WF benchmarks may help alleviate groundwater scarcity and pollution, in a case study for Iran. We advance the field of WF assessment by developing WF benchmark levels for crop production, which we successively use to assess potential groundwater saving, quality improvement and economic water productivity gains. First, we calculate climate-specific WF benchmark levels for both total blue water footprints and nitrogen-related grey groundwater footprints for 26 crops, for all years in the period 1980-2010, at 5 × 5 ′ spatial resolution. Second, we estimate the water saving potential for total blue water resources and for groundwater resources specifically, as well as the grey groundwater footprint reduction potential. Finally, we compare mean economic water productivities of crop production in the past with productivities if WFs are reduced to benchmark levels. We find that groundwater comprises up to 83% of total blue water consumption of irrigated crops, with the highest share in arid areas and in cereals. Aquifers are under significant to severe stress, except in the dry sub-humid zone, where irrigation mainly relies on surface water. Reducing WFs of crops to 25th percentile benchmark levels can save 32% of groundwater compared to the reference year 2010, and lower the nitrogen-related grey groundwater footprint by 23%. Moreover, it would increase average economic groundwater productivity in Iran by 20% for cereals, and 59% for nuts. We conclude that reducing WFs to climate-specific benchmark levels in a water-stressed country is a promising way to alleviate overexploitation of aquifers and increase national food security.

Capping Human Water Footprints in the World's River Basins

“…After all, a strategic pathway to conserve limited water resources in scarce basins is to increase water productivity in basins that still have the potential for it, e.g., by relocating crops (Pastor et al, ; Qin et al, ). One means to boost water productivity across basins is to formulate WF benchmarks for water‐using activities, i.e., a reasonable amount of water consumption per activity (Karandish et al, ). Another would be to use green water resources more productively (Schyns et al, ).…”

Socioeconomic benefits of conserving Iran’s water resources through modifying agricultural practices and water management strategies

“…EFR is estimated based on Richter et al ( 2012 ), as a constant fraction of natural runoff Hoekstra et al ( 2011 ) WF benchmark WF benchmark Minimum attainable WF in the location and time that the considered crop is grown. We obtained the climate-specific benchmark levels for the considered crops from Karandish et al ( 2018 ) Inefficient blue WF Inefficient blue water consumption occurs when the crop’s water footprint goes beyond its benchmark level Hoekstra et al ( 2011 ) Unsustainable blue WF blue WF minus blue water availability Hoekstra et al ( 2011 ) Blue water scarcity BWS It is an indicator of water scarcity which compares actual blue WF with the sustainable one. Different BWS classes are defined by Mekonnen and Hoekstra ( 2016 ), which are summarized in Table 3 Mekonnen and Hoekstra ( 2016 ) Attainable yield Y att The best yield achieved through skillful se of the best available technology under a given climate condition.…”

“…Crop’s blue water consumption is inefficient when it goes beyond its benchmark levels. We obtained the climate-specific benchmark levels for the considered crops from Karandish et al ( 2018 ). Per crop, per province, and per month, the inefficient blue WF was then determined as the difference between actual and benchmark WFs of the considered crops.…”

Water Footprint Assessment: towards water-wise food systems

“…Another advantage is that these models often include possibilities to simulate the effect of alternative irrigation (irrigation scheduling and application technique) and field (mulching, tillage, bunds) management options on the WF of a crop. It is for these reasons that in recent years, crop modeling has become the new standard in WFA (Chouchane, Krol, & Hoekstra, 2018b;Chukalla, Krol, & Hoekstra, 2015, 2017Gobin et al, 2017;Hogeboom & Hoekstra, 2017;Karandish, Hoekstra, & Hogeboom, 2018;Masud, McAllister, Cordeiro, & Faramarzi, 2018;Masud, Wada, Goss, & Faramarzi, 2019;Nouri, Stokvis, Galindo, Blatchford, & Hoekstra, 2019;Zhuo, Mekonnen, Hoekstra, & Wada, 2016c). The disadvantages of crop models are the higher input data requirements and computational demands, which makes their use for high spatial resolution modeling at large geographic scales (countries, river basins, global) challenging.…”

“…So the key question is: what producers can we compare? Recent studies have grouped and compared producers that operate in similar climates (Karandish et al, 2018;Mekonnen, Hoekstra, Neale, Ray, and Yang, 2020;Zhuo, Mekonnen, and Hoekstra, 2016a) and/or on similar soils (Zhuo et al, 2016a), and by separating rainfed and irrigated agricultural systems . However, no matter what spatial scope one takes in grouping producers, within that scope there will still be variability from place to place.…”