Monitoring of forest virtual water in Hunan Province,China, based on HJ-CCD remote-sensing images and pattern analysis

Virtual water has become an important part of global water supply and demand and has led to the globalization of water. Virtual water research most mainly focused on the field of agriculture. Minimal attention has been devoted to forest virtual water (FVW). To our knowledge, no research on the monitoring and analysis of FVW through remote-sensing technology has been conducted. In this study, based on object-oriented technology and through the use of 30 scenes from multi-temporal Chinese HJ-CCD images, we monitored FVW in Hunan Province, China, in 2010 and analysed the pattern of FVW. Results showed that the amount of FVW is large and greater than that of entity water. Hunan Province had 5.83 × 10¹¹m³ FVW in 2010, which was 3.09 times the amount of agriculture and livestock. FVW was thrice as large as the total entity water, 4.07 times the amount of surface water, and 14.57 times the amount of underground water in Hunan Province. The distribution of FVW in Hunan Province is uneven and presents a trend that gradually increases from northeast to southwest; nevertheless, the trend is reasonable and in favour of alleviating and optimizing the pattern of water resources. Our analysis indicated that we need to improve the cognition of virtual water and pay due attention to FVW from the perspective of water management and allocation. Our results also indicated that forest and woody products are water intensive. An efficient method of balancing FVW and other uses of water is thus required; control and management of water consumption in forests should also be implemented under the condition of protecting the environment. For China, woody forest products should be mainly imported to improve water-use efficiency and relieve the shortage of water. Meanwhile, remote-sensing technology is a useful tool, and Chinese HJ-CCD images are an important data source for the estimation of FVW.