As one of the three biggest irrigation district in China, Hetao irrigation district locates
in the inland arid zone in Northwest China. Due to the decrease of water diversion quota as
well 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 should
improve the agriculture water resources management level. Water footprint is the forefront
and hot topic of water resource management research worldwide. The water footprint
concept provides a new approach for assessing water resource utilization (type, amount
and efficiency) in agriculture. Therefore, the application of water footprint in water-saving
agriculture will extend the agricultural water management and evaluation systems. This
dissertation takes Hetao Irrigation District as its research area. Through the study of the
spatial-temporal variation of water footprint of crop production in Hetao Irrigation District,
it will contribute to provide some references for agricultural water resources management
at the irrigation district scale. Firstly, this study discussed the scientific connotation of
water footprint of crop production based on the existing water footprint theory system.
Secondly, in view of shortcoming of existing quantification method, this study put forward
a modified method of quantifying the water footprint of crop production at irrigation
district scale. The loss of irrigation water during the transmission and distribution process
from the water sources to field was taken into account in this modified method. And then
by using this method, this study quantified the water footprint (blue and green water
footprint) of 10 crops in Hetao Irrigation District from 1960 to 2008. Thirdly, the study
analyzed the spatial-temporal variation of water footprint of crop production by using GIS
platform. Finally, the study quantified the driving forces that caused the variation of water
footprint 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 the
application of water footprint theory in agricultural water resources management at the
irrigation district scale. The following main conclusions can be drawn:
(1) This study put forward a modified calculation method of water footprint of
crop production at Irrigation District scale.
In view of the shortcoming of existing calculation method based on crop water
requirement, this study presented a modified method for quantifying the water footprint for
crop production. In order to reflect the actual water consumption during the crop
production process, the loss of irrigation water during the transmission and distribution
process from the water sources to field was taken into account. It could reflect the actual
water consumption and water use efficiency of local region. Therefore, it could reflect the
regional agriculture water use efficiency and agricultural production level.
(2) This study analyzed the temporal and spatial variation of water footprint of
crop production and its blue-green components.
Based on the calculation method of water footprint, this study quantified the water
footprint of 10 crops in Hetao Irrigation District in nearly 50 years. Then, it analyzed the
temporal and spatial variation of water footprint and its blue-green components for the 10
crops. Results indicated that most crops had downward trend over the study period. Since
the agricultural production and irrigation project were at a comparatively low level in
1960s in Hetao irrigation district, the crop yield per unit area and irrigation water use
efficiency were relative low. Consequently, the water footprint of crops stayed at
historically high levels. With the improvement of agricultural productivity level and
irrigation system, the crop yield per unit area and irrigation water use efficiency have
obtained great enhancement. Under the combined influence of increasing crop yield per
unit area and agricultural water use efficiency, the water footprint of most crops showed
obvious downward trends. From the perspective of water footprint components, the
proportions of the blue water footprint in total water consumption were relatively high
(more than 80%) in most of the 10 crops, whereas those of the green water footprint were
relatively small (<15.00%).
Taking the county as spatial analysis unit, this study calculated and analyzed the water
footprint of the 10 crops and their blue-green components of the 5 counties in Hetao Irrigation District. The results showed that the regional differences of water footprint for
the 5 counties were significant. The analysis indicated that spatial differences of climatic
condition, agricultural production and irrigation level leaded to the diversity of water
footprint of crop production among the 5 counties. The high value was located in Linhe
County where with a high agriculture production level. Meanwhile, the Wulate County had
a higher share of green water footprint due to the higher precipitation in Hetao Irrigation
District. Due to the non-synchronized development of agricultural production and
irrigation level among the 5 counties during the study period, the spatial distribution of
water footprint of crop production was changed in each decade.
(3) Through this research, the main influence factors of water footprint for crop
production were determined and quantified.
By combining qualitative analysis and quantitative analysis, this study explored the
influence factors of water footprint of crop production. The results showed that the
contribution rate of climatic factors were relatively small. It signified that the climatic
factors were not the dominate factors that cause the decline of water footprint of crop
production during the study period for the total contribution rate of the climatic factors was
only 6.90%, while the total contribution rate of the agricultural inputs factors was 84.31%.
The contribution rates of fertilizer, utilization coefficient of irrigation water and
agricultural machinery were 34.89%, 31.87% and 17.55%, respectively. It suggests that the
water 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 variation
where the crop is grown.
The present study put forward a modified calculation method to quantify the water
footprint of crop. On this basis, this paper calculated the water footprint of major crops in
Hetao irrigation district, China. Then, it evaluated the influencing factors that caused the
variability of crop water footprint during the study period. The results of this study would
contribute to improving the agricultural water management level and providing preparatory
theory for establishing the water footprint control standard. As research continues, we are
aim to provide the scientific and reasonable index system for implementing stringent water
resources management system in future.
Key words: water footprint; spatial-temporal variation; influence factor analysis; Hetao