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Article

Long-Term (1990–2013) Changes and Spatial Variations of Cropland Runoff across China

1
College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China
2
Agriculture Ministry Key Laboratory of Healthy Freshwater Aquaculture, Key Laboratory of Fish Health and Nutrition of Zhejiang Province, Zhejiang Institute of Freshwater Fisheries, Huzhou 313001, China
3
Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
4
Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, Zhejiang University, Hangzhou 310058, China
*
Author to whom correspondence should be addressed.
Academic Editor: Marco Franchini
Water 2022, 14(18), 2918; https://doi.org/10.3390/w14182918
Received: 22 August 2022 / Revised: 10 September 2022 / Accepted: 13 September 2022 / Published: 17 September 2022
(This article belongs to the Section Hydrology)
Quantitative information on regional cropland runoff is important for sustainable agricultural water quantity and quality management. This study combined the Soil Conservation Service Curve Number (SCS-CN) method and geostatistical approaches to quantify long-term (1990–2013) changes and regional spatial variations of cropland runoff in China. Estimated CN values from 17 cropland study sites across China showed reasonable agreement with default values from the National Engineering Handbook (R2 = 0.76, n = 17). Among four commonly used geostatistical interpolation methods, the inverse distance weighting (IDW) method achieved the highest accuracy (R2 = 0.67, n = 209) for prediction of cropland runoff. Using default CN values and the IDW method, estimated national annual cropland runoff volume and runoff depth in 1990–2013 were 253 ± 25 km3 yr−1 and 182 ± 15 mm yr−1, respectively. Estimated cropland runoff depth gradually increased from the drier northwest inland region to the wetter southeast coastal region (range: 2–1375 mm yr−1). Regionally, eastern, central and southern China accounted for 39% of the cultivated area and 53% of the irrigated land area and contributed to 68% of the national cropland runoff volume. In contrast, northwestern, northern, southwestern and northeastern China accounted for 61% of the cultivated area and 47% of the irrigated land area and contributed to 32% of the runoff volume. Rainfall was the main source (72%) of cropland runoff for the entire nation, while irrigation became the main source of cropland runoff in drier regions (northwestern and southwestern China). Over the 24-year study period, estimated cropland runoff depth showed no significant trends, whereas cropland runoff volume and irrigation-contributed percentages decreased by 7% and 35%, respectively, owing to implementation of water-saving irrigation technologies. To reduce excessive runoff and increase water utilization efficiencies, regionally specific water management strategies should be further promoted. As the first long-term national estimate of cropland runoff in China, this study provides a simple framework for estimating regional cropland runoff depth and volume, providing critical information for guiding developments of management practices to mitigate agricultural nonpoint source pollution, soil erosion and water scarcity. View Full-Text
Keywords: cropland; runoff estimation; SCS-curve number; spatial interpolation; rainfall; irrigation cropland; runoff estimation; SCS-curve number; spatial interpolation; rainfall; irrigation
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MDPI and ACS Style

Zhang, Y.; Jiao, X.; Wei, Y.; Wu, H.; Pan, Z.; Liu, M.; Yuan, J.; Ni, M.; Zhou, Z.; Zeng, L.; Chen, D. Long-Term (1990–2013) Changes and Spatial Variations of Cropland Runoff across China. Water 2022, 14, 2918. https://doi.org/10.3390/w14182918

AMA Style

Zhang Y, Jiao X, Wei Y, Wu H, Pan Z, Liu M, Yuan J, Ni M, Zhou Z, Zeng L, Chen D. Long-Term (1990–2013) Changes and Spatial Variations of Cropland Runoff across China. Water. 2022; 14(18):2918. https://doi.org/10.3390/w14182918

Chicago/Turabian Style

Zhang, Yufu, Xinyi Jiao, Yinghuai Wei, Hao Wu, Zheqi Pan, Mei Liu, Julin Yuan, Meng Ni, Zhiming Zhou, Lingzao Zeng, and Dingjiang Chen. 2022. "Long-Term (1990–2013) Changes and Spatial Variations of Cropland Runoff across China" Water 14, no. 18: 2918. https://doi.org/10.3390/w14182918

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