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Contrasting effects of increasing irrigation efficiency on hydrological drought based on hydrological scenario simulations
Journal of Hydrology ( IF 5.9 ) Pub Date : 2024-10-29 , DOI: 10.1016/j.jhydrol.2024.132261 Hui Cheng, Wen Wang, Inge de Graaf, Jingxuan Lu, Saskia van der Kooij, Jeroen Vos, Yuan Yao, Pieter van Oel
Journal of Hydrology ( IF 5.9 ) Pub Date : 2024-10-29 , DOI: 10.1016/j.jhydrol.2024.132261 Hui Cheng, Wen Wang, Inge de Graaf, Jingxuan Lu, Saskia van der Kooij, Jeroen Vos, Yuan Yao, Pieter van Oel
Over-exploitation of water resources leads to water scarcity and aggravation of hydrological drought. An approach to addressing the problem is to invest in increasing irrigation efficiency (IE). However, higher IE may lead to the paradox of IE, that is, after increasing IE, irrigation water consumption (IWC) could increase rather than decrease. An important cause of the paradox of IE is that increasing IE may lead to an increase in irrigation area (IA). Therefore, an improved understanding of the impacts of such practices on hydrological drought is needed. This study used the PCR-GLOBWB 2.0 model to investigate the effects of increasing IE on hydrological drought for the catchment above Bengbu in the Huaihe River Basin in central eastern China. The hydrological drought was simulated under three scenarios, i.e., a baseline scenario in which IE remains unchanged, an IE increases scenario, and an IE & IA increase scenario. The results show that increasing IE has two contrasting effects: aggravation and alleviation of hydrological drought. For instance, the increase in IE (from 0.562 to 0.601 in Henan, 0.482 to 0.544 in Anhui, and 0.464 to 0.522 in Hubei province) from 2009 to 2019 reduced standardized drought streamflow deficit (SDSD) by about 5 ∼ 60 % in the central parts of the study area, whereas in the northern edge of the study area, it intensified SDSD even by more than 80 %. When water availability (WA) is high and can meet most of the crop water demand, increasing IE will lead to a situation in which the increase of IWC is less than the decrease of irrigation water withdrawal (IWW). In this situation, increasing IE alleviates the hydrological drought as intended. However, when water resources are relatively scarce with limited WA and cannot meet most of the crop water demand, increasing IE could lead to a paradoxical situation where the increase of IWC is higher than the decrease of IWW and thereby aggravates the hydrological drought. Also, increasing IE can aggravate the hydrological drought in water-receiving areas by reducing water supply from outside water supply regions. Results show that the impact of increasing IE and IA on hydrological drought is also two-sided, but the aggravating effect is dominant because the increase in IA leads to a significant increase in IWW and IWC. However, when the irrigation system restricts the increase of IA (the IA cannot increase or only slightly), the intensification effect of increasing IE and IA on hydrological drought will be weakened, and may even alleviate the hydrological drought. These results underline the importance of considering consequences at both local and basin scales, particularly for periods during and following drought, when policy makers consider the promotion of water-saving measures at irrigation-system level.
更新日期：2024-10-29
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