In this study,two types of El Nio events are distinguished and the correlations between the respective precipitation,temperature,and runoff are analyzed by a 5-point moving average method.Also,changes of the temperature,precipitation,and runoff from mountainous watersheds of the Hexi Corridor region caused by these two types of El Nio events from 1959 to 2005 are studied by the anomaly analysis method.The results indicate that the Hexi Corridor region is strongly influenced by El Nio:rising temperatures and decreasing precipitation and runoff are features of the first El Nio pattern,while decreasing temperature and increasing precipitation and runoff characterise the second pattern.The responses of temperature to El Nio events are stronger in plains than in mountain regions,but the responses of precipitation are obvious in both types of regions.The response of runoff to El Nio events is lower than the precipitation and temperature response because runoff from mountainous watersheds has a complex generation and concentration process.
Water storage has important significance for understanding water cycles of global and local domains and for monitoring climate and environmental changes.As a key variable in hydrology,water storage change represents the sum of precipitation,evaporation,surface runoff,soil water and groundwater exchanges.Water storage change data during the period of 2003-2008 for the source region of the Yellow River were collected from Gravity Recovery and Climate Experiment(GRACE)satellite data.The monthly actual evaporation was estimated according to the water balance equation.The simulated actual evaporation was significantly consistent and correlative with not only the observed pan(20 cm)data,but also the simulated results of the version 2 of Simple Biosphere model.The average annual evaporation of the Tangnaihai Basin was 506.4 mm,where evaporation in spring,summer,autumn and winter was 130.9 mm,275.2 mm,74.3 mm and 26.1 mm,and accounted for 25.8%,54.3%,14.7% and 5.2% of the average annual evaporation,respectively.The precipitation increased slightly and the actual evaporation showed an obvious decrease.The water storage change of the source region of the Yellow River displayed an increase of 0.51 mm per month from 2003 to 2008,which indicated that the storage capacity has significantly increased,probably caused by the degradation of permafrost and the increase of the thickness of active layers.The decline of actual evaporation and the increase of water storage capacity resulted in the increase of river runoff.
Min XUBaiSheng YEQiuDong ZHAOShiQing ZHANGJiang WANG
Diurnal minor and trace elements in glacial outflow water draining the Qiyi Glacier and associated hydrological controls as well as the filtration effects on water chemistry were examined. Results show that major ions, Li, Sr, and Ba are exported predominately as mobile monovalent or divalent ions and are controlled by hydrological variations over the diurnal cycle exhibiting an inverse concentration with discharge, suggesting that Li, Sr, and Ba can be used as tracers in subglacial hydrological investigations. Conversely, other elements (e.g. Fe, Al, and Cr) exhibit variations that are not strongly correlated with the discharge reflecting the physicochemical controls. The non-filtered operation appears not to strongly influence Sr and Ba, but has an effect on some elements such as Fe, Al, V, Ti, and Co, indicating that these changed elements are transported in particulate forms and thus their concentrations are highly dependent on particulate numbers in solutions. This implies that the immediate filtration after sampling is essential in hydrochemical studies at Alpine glacial basins due to subsequent mineral dissolution.
LI XiangYingQIN DaHeJING ZheFanLI YueFangWANG NingLian
