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, which is beset with ecological and environmental problems that affect economic and social development. Hence, the hydrological impact factors (underground water level and surface runoff) in this region need to be investigated. The current study reconstructed the runoff sequences from the southwest edge of the Liaohe River to 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 used for 183 years. For the past 180 years, the runoff has experienced six and four consecutive wet and dry seasons, respectively. From 1982 to 2005, the runoff reached the longest stream segment of a continuous low-flow runoff, with a mean average runoff of only 63.58% for the entire period. The runoff had 3, 11, 15, 24, and 30-year quasi-periodic variations, consistent with changes in similar areas worldwide. The change was gentler from 1826 to 1917. In 1956, the runoff increased, then significantly decreased for nearly 50 years. The drop rate was