The Water Footprint of Agriculture in Duero River Basin

Abstract

Abstract:The aim of this paper is to evaluate the green, blue and grey water footprint (WF) of crops in the Duero river basin. For this purpose CWUModel was developed. CWUModel is able to estimate the green and blue water consumed by crops and the water needed to assimilate the nitrogen leaching resulting from fertilizer application. The total WF of crops in the Spanish Duero river basin was simulated as 9473 Mm 3 /year (59% green, 20% blue and 21% grey). Cultivation of crops in rain-fed lands is responsible for 5548 Mm 3 /year of the WF (86% green and 14% grey), whereas the irrigated WF accounts for 3924 Mm 3 /year (20% green, 47% blue and 33% grey). Barley is the crop with the highest WF, with almost 37% of the total WF for the crops simulated for the basin, followed by wheat (17%). Although maize makes up 16% of the total WF of the basin, the blue and grey components comprise the 36% of the total blue and grey WF in the basin. The relevance of green water goes beyond the rain-fed production, to the extent that in long-cycle irrigated cereals it accounts for over 40% of the total water consumed. Nonetheless, blue water is a key component in agriculture, both for production and economically. The sustainability assessment shows that the current blue water consumption of crops causes a significant or severe water stress level in 2-5 months of the year. The anticipated expansion of irrigation in the coming years could hamper water management, despite the Duero being a relatively humid basin.

Appraisal of the water footprint of irrigated agriculture in a semi-arid area: The Segura River Basin

“…However, in all of them, rainwater evapotranspiration is the green component of the WF (WF Green [volume/time]), the net irrigation water consumed or evapotranspired is the blue component (WF Blue [volume/time]) and the excess of fertilisers/pesticides that ends up in water bodies determines the grey part (WF Grey [volume/time]). Once the WF has been assessed for each crop, the results are aggregated for all of the area under analysis [ 8 , 14 , 20 ].…”

“…Despite the large number of studies on the WF in agriculture, there are criticisms of the methodologies applied and its usefulness in the management of water resources [ 17 – 19 ]. These derive from the limitations of the methodologies that normally are applied to determine this indicator (see [ 14 , 20 ], among others). For local or regional cases, the following stand out: it is assumed that there are always blue water resources for an optimal supply and that these resources always have hydraulic infrastructure that enables them to reach the irrigated areas.…”

Coupling the water footprint accounting of crops and in-stream monitoring activities at the catchment scale

“…The WF blue (m 3 t −1 ) was calculated by dividing the total volume of blue water used – CWU blue (m 3 ha −1 y −1 ) – by the quantity of the annual production – Y (t ha −1 y −1 ): The CWU blue (mm time −1 ) was calculated by performing another soil-water balance (Eq. (9) ) on a 10-d basis, and irrigation ( I i ) was considered, as proposed by Hoekstra et al [ 28 ] and applied by Mekonnen and Hoekstra [ 39 ], de Miguel et al [ 48 ], Zhuo et al [ 46 ] and Rulli and D’Odorico [ 49 ]. I i values could be deduced from the above-mentioned interviews.…”

Water Footprints and Sustainable Water Allocation

“…The paper by De Miguel et al [7] considers WF at the river basin level-still the most common level for water analyses-and takes a production rather than a consumption perspective, by considering the sustainability of the WF of crop production in the Duero River Basin in Spain. Their analysis shows that the current blue WF of crop growing causes a significant or severe water stress level in two to fives months per year and suggests that the foreseen future growth of irrigation could impede a movement to more sustainable water use, despite the Duero basin being relatively humid.…”