Research On The Spatial-Temporal Variation Of Water Footprint Of Crop Production In Nearly50Years In Hetao Irrigation District

As one of the three biggest irrigation district in China, Hetao irrigation district locatesin the inland arid zone in Northwest China. Due to the decrease of water diversion quota aswell as the low water use efficiency, the agriculture water use is under enormous pressure.In order to make the water use more efficient and sustainable, the irrigation district shouldimprove the agriculture water resources management level. Water footprint is the forefrontand hot topic of water resource management research worldwide. The water footprintconcept provides a new approach for assessing water resource utilization (type, amountand efficiency) in agriculture. Therefore, the application of water footprint in water-savingagriculture will extend the agricultural water management and evaluation systems. Thisdissertation takes Hetao Irrigation District as its research area. Through the study of thespatial-temporal variation of water footprint of crop production in Hetao Irrigation District,it will contribute to provide some references for agricultural water resources managementat the irrigation district scale. Firstly, this study discussed the scientific connotation ofwater footprint of crop production based on the existing water footprint theory system.Secondly, in view of shortcoming of existing quantification method, this study put forwarda modified method of quantifying the water footprint of crop production at irrigationdistrict scale. The loss of irrigation water during the transmission and distribution processfrom the water sources to field was taken into account in this modified method. And thenby using this method, this study quantified the water footprint (blue and green waterfootprint) of10crops in Hetao Irrigation District from1960to2008. Thirdly, the studyanalyzed the spatial-temporal variation of water footprint of crop production by using GISplatform. Finally, the study quantified the driving forces that caused the variation of waterfootprint for crop production during the study period by using path and contribution rate analysis, and it also put forward some control measures and preliminary discussion of theapplication of water footprint theory in agricultural water resources management at theirrigation district scale. The following main conclusions can be drawn:(1) This study put forward a modified calculation method of water footprint ofcrop production at Irrigation District scale.In view of the shortcoming of existing calculation method based on crop waterrequirement, this study presented a modified method for quantifying the water footprint forcrop production. In order to reflect the actual water consumption during the cropproduction process, the loss of irrigation water during the transmission and distributionprocess from the water sources to field was taken into account. It could reflect the actualwater consumption and water use efficiency of local region. Therefore, it could reflect theregional agriculture water use efficiency and agricultural production level.(2) This study analyzed the temporal and spatial variation of water footprint ofcrop production and its blue-green components.Based on the calculation method of water footprint, this study quantified the waterfootprint of10crops in Hetao Irrigation District in nearly50years. Then, it analyzed thetemporal and spatial variation of water footprint and its blue-green components for the10crops. Results indicated that most crops had downward trend over the study period. Sincethe agricultural production and irrigation project were at a comparatively low level in1960s in Hetao irrigation district, the crop yield per unit area and irrigation water useefficiency were relative low. Consequently, the water footprint of crops stayed athistorically high levels. With the improvement of agricultural productivity level andirrigation system, the crop yield per unit area and irrigation water use efficiency haveobtained great enhancement. Under the combined influence of increasing crop yield perunit area and agricultural water use efficiency, the water footprint of most crops showedobvious downward trends. From the perspective of water footprint components, theproportions of the blue water footprint in total water consumption were relatively high(more than80%) in most of the10crops, whereas those of the green water footprint wererelatively small (<15.00%).Taking the county as spatial analysis unit, this study calculated and analyzed the waterfootprint of the10crops and their blue-green components of the5counties in Hetao Irrigation District. The results showed that the regional differences of water footprint forthe5counties were significant. The analysis indicated that spatial differences of climaticcondition, agricultural production and irrigation level leaded to the diversity of waterfootprint of crop production among the5counties. The high value was located in LinheCounty where with a high agriculture production level. Meanwhile, the Wulate County hada higher share of green water footprint due to the higher precipitation in Hetao IrrigationDistrict. Due to the non-synchronized development of agricultural production andirrigation level among the5counties during the study period, the spatial distribution ofwater footprint of crop production was changed in each decade.(3) Through this research, the main influence factors of water footprint for cropproduction were determined and quantified.By combining qualitative analysis and quantitative analysis, this study explored theinfluence factors of water footprint of crop production. The results showed that thecontribution rate of climatic factors were relatively small. It signified that the climaticfactors were not the dominate factors that cause the decline of water footprint of cropproduction during the study period for the total contribution rate of the climatic factors wasonly6.90%, while the total contribution rate of the agricultural inputs factors was84.31%.The contribution rates of fertilizer, utilization coefficient of irrigation water andagricultural machinery were34.89%,31.87%and17.55%, respectively. It suggests that thewater footprint of a crop, to a large extent, is determined by agricultural management(agricultural inputs) and irrigation level rather than by the agro-climate and its variationwhere the crop is grown.The present study put forward a modified calculation method to quantify the waterfootprint of crop. On this basis, this paper calculated the water footprint of major crops inHetao irrigation district, China. Then, it evaluated the influencing factors that caused thevariability of crop water footprint during the study period. The results of this study wouldcontribute to improving the agricultural water management level and providing preparatorytheory for establishing the water footprint control standard. As research continues, we areaim to provide the scientific and reasonable index system for implementing stringent waterresources management system in future.