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Evaluating the effect of irrigation techniques and strategies on the water footprint of crops using APEX and AQUACROP models.

Rodink, D. (2017) Evaluating the effect of irrigation techniques and strategies on the water footprint of crops using APEX and AQUACROP models.

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Abstract:This research is focused on evaluating the effect of irrigation strategies on the water footprint for two different crop types; wheat and maize, using two models; AquaCrop and APEX. The research is done for a case study for the region of Badajoz, Spain. Climatic data for the years 1993-2012 were provided by my supervisor A.D.Chukalla. The models were set up with input data such as climatic data, soil data and irrigation options. There are different types of irrigation strategies and techniques possible. In general there are four major irrigation strategies and techniques; rain-fed irrigation, full irrigation, deficit irrigation and supplementary irrigation. The most common irrigation techniques are furrow irrigation, sprinkler irrigation, drip irrigation and sub surface drip irrigation. The scope of the irrigation strategies and techniques was on rain fed irrigation and full irrigation, using furrow and sprinkler irrigation techniques. To enable comparison between the two models the research focusses on the blue and green components of the water footprint. Their sum is called the consumptive water footprint. The water footprint method usually focusses on all three components; green water footprint, blue water footprint and grey water footprint. Since the AquaCrop model is unable to determine the grey water footprint as results of pollution by used fertilizers and pesticides the research focusses on the remaining green and blue water footprint. Instead of speaking about the total water footprint we use the term consumptive water footprint. The yield and evapotranspiration of the crops are simulated for different irrigation techniques and strategies. The evapotranspiration is the sum of crop evaporation and transpiration and is expressed in mm and the yield produces is simulated in ton/ha. To determine the blue and green components of the water footprint the evapotranspiration has to be separated into a green and blue component. To do so, the assumption is made that with rain-fed strategy all the evapotranspiration is green (due to the absence of irrigation water), and that the same amount of green evapotranspiration can be applied when using irrigation techniques and strategies that do apply irrigation water. The AquaCrop model shows consistent results for both maize and wheat production in the study area with sprinkler irrigation being the most efficient strategy and technique and rain fed having the highest water footprint. The APEX model does not show consistent results. The irrigation strategy has no impact on the water footprints for wheat production, and the water footprints for rain fed cropping are too high. The results of the study show a major difference in terms of green, blue and consumptive water footprint when comparing the models. The AquaCrop model results show a consistent ranking in irrigation techniques and strategies in terms of efficiency, both for wheat and maize production. The consumptive water footprint of wheat is the lowest for the sprinkler technique with full irrigation strategy (892 m3ton-1), followed by the furrow technique with full irrigation strategy (962 m3ton-1) and rain fed strategy (2006 m3ton-1). For maize production a same pattern is observed; sprinkler technique with full irrigation strategy (455 m3ton-1), furrow technique with full irrigation strategy (514 m3ton-1) and rain fed strategy (715 m3ton- 1) as least efficient. Compared to rain-fed crop production of wheat, applying sprinkler and furrow irrigation techniques with full irrigation strategy reduces the consumptive water footprint by 55% and 52% respectively. Compared to rain-fed crop production of maize, applying sprinkler and furrow irrigation techniques with full irrigation strategy reduces the consumptive water footprint by 36% and 28% respectively. This indicates that using sprinkler or furrow irrigation techniques with full irrigation strategy for the studied crops in the 4 study area is more efficient than rain-fed cropping. The results from the AquaCrop model are compatible with benchmark studies. For further research the output of the APEX has to be carefully checked. It seems like the model gives the exact same output in terms of yield and evapotranspiration or both sprinkler and furrow irrigation strategies. The consumptive water footprint for rain-fed strategy for wheat (8688 m3ton-1) and maize (4566 m3ton-1) are four to five times higher compared to the AquaCrop model. To make the results more comparable, the daily output of the AquaCrop model can be used instead of the output on the interface of the model (growth period) to determine the yearly average yield and evapotranspiration.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
Link to this item:http://purl.utwente.nl/essays/74573
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