Water Level Change of the West Juyan Lake in the Past 100 Years Recorded in the Tree Ring of the Shrubs in the Lake Banks
XIAO Sheng-chun,XIAO Hong-lang,ZHOU Mao-xian,SI Jian-hua,ZHANG Xiao-you (Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou Gansu 730000, China)
West Juyan Lake is one of the terminal lakes of the Heihe River, which has been dried since 1960. There are three sandbar banks on the southwest of the lake, in the area of 42°20′15.56″～42°21′8.81″ N and 100°41′50.945″～100°42′30.63″ E. The shrubs in the banks of the West Juyan Lake are mainly Tamarix romasisima, which invaded along with the lake degradation. There are 53 samples taken from the banks. All the samples were sanded, polished and cross-dated with the dendrochronological methods. Tree ring width is measured with microscope in 0.01 mm precision. The COFECHA program checked the result of cross-date; the ARSTAN program achieved the standard chronology. Based on the correlation analysis, which includes the tree ring standard chronology of the West Juyan Lake and the elements of meteorology and hydrology in the Ejina Banner, Inner-Mongolia, it is found that the standard chronology has a positive correlation with the average grounder-water level in the lower reaches of the West River from May to August. Saltcedar (also named phreatophyte) on the condition without frequent floods to inundate mainly lives on the deep groundwater. So, the correlation of the tree ring chronology and the grounder-water level change has a definite biological significance. A regression model was found using the correlation. Upon it, the water level change of the West Juyan Lake from May to August was reconstructed for the past 100 years. Through verification with the historical documents, the instrument records of the river runoff and the precipitation, the reconstructed result of the water level change is credible. Combined with the historical fact that the West Juyan Lake had dried during 1960—1962, and the reconstructed water-level change curve, the 100 years can be divided into water level change and groundwater level change phases. Among them, the water level rising stages were 1932—1952 and 1956—1958, the water level declining stages were 1916—1932, 1952—1956 and 1958—1960, with the intervals of 20, 2, 12, 5 and 2 years; The groundwater level rising stages were 1973—1981 and 1992—1999, the groundwater level declining stages were 1960—1973, 1981—1992 and 1999—2002, with the intervals of 8, 1, 13, 15 and 5 years.
【Fund】： 中国科学院知识创新工程项目(KZCX1 09 05);; 国家自然科学基金项目(40371009);; 国家西部项目(2001BA901A42)资助
【CateGory Index】： P339
【CateGory Index】： P339