Tree ring-based reconstruction of October to November runoffs in the Jiaolai River since 1826

Abstract. The Horqin Sandy Land is a typical desertification region in China hounded by ecological and environmental problems, which continue to affect economic and social development.Hence,hydrological climate changes in this region need to be investigated. The current study reconstructed the runoff sequences in the southwest edge of the LiaoHe River into the XiaWa station of the JiaoLai River during the months of October to November from 1826 to 2005. A comprehensive timeline for the regional tree wheel width of the Horqin Sandy Land was employed. The timeline has been in use for 183 yr. For the past 180 yr, the runoff has experienced six and four consecutive Feng and dry sections, respectively. From 1982 to 2005, the runoff reached the longest section of a continuous low-flow runoff, with the mean average runoff amounting to only 63.58% of the entire period. Runoff has 3-, 11-, 15-, 24-, and 30-yr quasi-periodic variations, consistent with changes in similar areas worldwide. The period of 1826 to 1917 presents a more gentle change. In 1956, the runoff increased, and then significantly decreased for nearly 50 yr. The drop rate is 1.7766 million m³/10 yr, which shows a consistent downward trend with the precipitation (14.74 mm/10 yr). The overall reduction in precipitation accounts for 29.86% of the initial value, which is far less than 75.58% of the runoff. If the runoff and precipitation drop continue, more extensive and longer ecological and environmental problems are foreseen to occur.