Preprints
https://doi.org/10.5194/essd-2024-2
https://doi.org/10.5194/essd-2024-2
29 Jan 2024
 | 29 Jan 2024
Status: this preprint is currently under review for the journal ESSD.

CIrrMap250: Annual maps of China’s irrigated cropland from 2000 to 2020 developed through multisource data integration

Ling Zhang, Yanhua Xie, Xiufang Zhu, Qimin Ma, and Luca Brocca

Abstract. Accurate maps of irrigation extent and dynamics are important to study food security and its far-reaching impacts on Earth systems and the environment. While several efforts have been made to map irrigated areas in China, few of them have provided multi-year maps, incorporated national land surveys, addressed data discrepancies, and considered the fraction coverage of irrigated cropland (i.e., the mixed pixel issue). In this study, we addressed these important gaps and developed new annual maps of China’s irrigated cropland from 2000 to 2020, named as CIrrMap250. We harmonized irrigated area statistics and land surveys and reconciled them with remote sensing data. The refined estimates of irrigated area were then integrated with multiple remote sensing data (i.e., vegetation indices, hybrid cropland product, and paddy field maps) and irrigation suitability map through a semi-automatic training approach. We then evaluated our CIrrMap250 maps using independently interpreted 20,000 reference locations, high-resolution irrigation water withdrawal data, and existing local to nationwide maps. Our evaluation results showed that CIrrMap250 agreed well with the reference points, with an overall accuracy of 0.79–0.88 for years 2000, 2010, and 2020, respectively. The CIrrMap250-estimated irrigated area can explain 50–60 % of the variance in irrigation water withdrawals across China. Our CIrrMap250 product showed superior performance than currently available ones (i.e., IrriMap_CN, IAAA, and GFSAD). CIrrMap250 revealed that China’s irrigated area has increased by about 180,000 km2 (or 25 %) from 2000 to 2020, with the majority (61 %) being water-unsustainable and occurring in regions facing high to severe water stress. Moreover, our product unveiled a noticeable northward shift of China’s irrigated area, attributed to substantial expansion in irrigated cropland across Northeast and Northwest China. The accurate representation irrigation area in CIrrMap250 will greatly support hydrologic, agricultural, and climate studies in China for improved water and land resources management.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Ling Zhang, Yanhua Xie, Xiufang Zhu, Qimin Ma, and Luca Brocca

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2024-2', Anonymous Referee #1, 20 Mar 2024
    • AC1: 'Reply on RC1', Lin Zhang, 08 Jun 2024
  • RC2: 'Comment on essd-2024-2', Anonymous Referee #2, 14 Jun 2024
Ling Zhang, Yanhua Xie, Xiufang Zhu, Qimin Ma, and Luca Brocca

Data sets

CIrrMap250: Annual maps of China’s irrigated cropland from 2000 to 2020 Ling Zhang, Yanhua Xie, Xiufang Zhu, Qimin Ma, and Luca Brocca https://doi.org/10.6084/m9.figshare.24814293.v1

Ling Zhang, Yanhua Xie, Xiufang Zhu, Qimin Ma, and Luca Brocca

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Short summary
This study outlines the development of annual maps of irrigated cropland in China from 2000 to 2020 (CIrrMap250) by integrating remote sensing data, irrigated area statistics and surveys, and irrigation suitability map. CIrrMap250 showed superior performance than the existing products. CIrrMap250 revealed that China’s irrigated area has increased by about 180,000 km2 from 2000 to 2020, with the majority being water-unsustainable and occurring in regions facing high to severe water stress.
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