Green and blue water footprint reduction in irrigated agriculture: effect of irrigation techniques, irrigation strategies and mulching

Abstract

Abstract. Consumptive water footprint (WF) reduction in irrigated crop production is essential given the increasing competition for freshwater. This study explores the effect of three management practices on the soil water balance and plant growth, specifically on evapotranspiration (ET) and yield (Y ) and thus the consumptive WF of crops (ET / Y ). The management practices are four irrigation techniques (furrow, sprinkler, drip and subsurface drip (SSD)), four irrigation strategies (full (FI), deficit (DI), supplementary (SI) and no irrigation), and three mulching practices (no mulching, organic (OML) and synthetic (SML) mulching). Various cases were considered: arid, semi-arid, sub-humid and humid environments in Israel, Spain, Italy and the UK, respectively; wet, normal and dry years; three soil types (sand, sandy loam and silty clay loam); and three crops (maize, potato and tomato). The AquaCrop model and the global WF accounting standard were used to relate the management practices to effects on ET, Y and WF. For each management practice, the associated green, blue and total consumptive WF were compared to the reference case (furrow irrigation, full irrigation, no mulching). The average reduction in the consumptive WF is 8-10 % if we change from the reference to drip or SSD, 13 % when changing to OML, 17-18 % when moving to drip or SSD in combination with OML, and 28 % for drip or SSD in combination with SML. All before-mentioned reductions increase by one or a few per cent when moving from full to deficit irrigation. Reduction in overall consumptive WF always goes together with an increasing ratio of green to blue WF. The WF of growing a crop for a particular environment is smallest under DI, followed by FI, SI and rain-fed. Growing crops with sprinkler irrigation has the largest consumptive WF, followed by furrow, drip and SSD. Furrow irrigation has a smaller consumptive WF compared with sprinkler, even though the classical measure of "irrigation efficiency" for furrow is lower.

Benchmark levels for the consumptive water footprint of crop production for different environmental conditions: a case study for winter wheat in China

“…Kumar et al, 2014;Jin et al, 2014;Abedinpour et al, 2012;Mkhabela and Bullock, 2012;Andarzian et al, 2011;Stricevic et al, 2011;Heng et al, 2009;Farahani et al, 2009;García-vila et al, 2009). AquaCrop has been applied in WF accounting at field (Chukalla et al, 2015), river basin (Zhuo et al, 2016a), and national level (Zhuo et al, 2016b) at high spatial resolution.…”

“…The green and blue WFs are determined by green and blue ET over the cropping period, respectively, divided by Y . Following Chukalla et al (2015) and Zhuo et al (2016a, b), the daily green and blue ET (mm) were separated by tracking the daily incoming and outgoing green and blue water fluxes at the boundaries of the root zone:…”

“…Mekonnen and Hoekstra (2014) followed the first approach and developed global benchmarks for both the consumptive (green plus blue) WF and the degradative (grey) WF for a large number of crops, based on estimated WF values for 1996-2005 at a spatial resolution of 5 by 5 arcmin. Chukalla et al (2015) followed the second approach and explored reduction potentials of consumptive WFs for a few crops by applying different types of alternative irrigation techniques and strategies and different types of alternative mulching practices. They found that the highest reduction (∼ 29 %) in the consumptive WF of a crop could be achieved when applying drip or subsurface drip irrigation in combination with deficit irrigation and synthetic mulching.…”

Marginal cost curves for water footprint reduction in irrigated agriculture: guiding a cost-effective reduction of crop water consumption to a permit or benchmark level

“…The fluxes into and from the root zone are runoff, infiltration, evapotranspiration, drainage and capillary rise. The green and blue fractions in total ET are calculated based on the green to blue water ratio in the soil moisture, which in turn is kept track of over time by accounting for how much green and blue water enter the soil moisture, following the accounting procedure as reported in Chukalla et al (2015).…”

“…WF reduction in irrigated crop production can be achieved through a range of measures, including a change in mulching practice or in irrigation technique or strategy. Chukalla et al (2015) studied the effectiveness of different combinations of irrigation technique, irrigation strategy and mulching practice in terms of WF reduction. No research thus far has been carried out regarding the costs of WF reduction.…”