Drivers of the irrigation water rebound effect: A case study of Hetao irrigation district in Yellow River basin, China

Improving irrigation systems to enhance irrigation efficiency is often considered an effective means of reducing water extraction. However, irrigation efficiency improvements do not always result in reductions in overall water extraction because of the irrigation water rebound effect (WRE). To better promote water conservation, it is necessary to clarify the drivers of the WRE. This study clarifies the drivers of the WRE by developing a 2 x 2 production model through a comparative static analysis. Then, a method for decomposing the WRE is constructed to quantify the drivers of the WRE with the logarithmic mean Divisia index (LMDI) approach. Finally, a case study of the WRE in the Hetao irrigation district in Yellow River basin of China is performed. The WRE can be divided into four effects: the product income effect, product substitution effect, factor income effect and factor substitution effect. These four effects illustrate the following four reasons why water extraction increases in response to irrigation efficiency improvements: sown area expansion, planting structure adjustment to include more water-intensive crops, irrigation proportion expansion and increase in irrigation intensity. In the case study, although the irrigation efficiency of the Hetao irrigation district improved from 1949 to 2017, the water extraction and consumption maintained an upward trend, leading to the WRE. The case study of Hetao irrigation district indicated that all the four effects increased the WRE , and the product income effect (expansion of the sown area) and the factor income effect (expansion of the irrigation proportion) were the main drivers of unrealized water savings in the Hetao irrigation district from 1949 to 2017. This study provides a framework for understanding the WRE and clearly identifies the locations where greater amounts of water are extracted despite irrigation efficiency improvements.