Baseflow, which represents the drainage of groundwater aquifers, is an essential component of runoff in hydrological basins. In the source region of the Yangtze River, the change of baseflow typically reflects the in-...Baseflow, which represents the drainage of groundwater aquifers, is an essential component of runoff in hydrological basins. In the source region of the Yangtze River, the change of baseflow typically reflects the in- teractions between groundwater system and climatic factors in cold and arid areas. With modified Kalinen separa- tion method, annual baseflow between 1957 and 2009 in this region was estimated and calculated. In comparison with the inner-annual variations of total streamflow, baseflow showed a weaker fluctuation. Before the 1980s, it was in a steady state; and after then, it demonstrated dramatic variations and large amplitudes. Based on the calculation results of baseflow, the real Morlet wavelet method was applied to reveal the periodical characteristics of baseflow as well as the precipitation and air temperature in the study area. It was found that annual baseflow has a 43-year trend as well as a 21-year period and a 7-year period. The 21-year period is most significant, with its wavelet coef- ficient having the largest fluctuation and amplitude. Summation of wavelet coefficients on these periods exhibits a similar change pattern with respect to that of annual baseflow. The summation curve takes a ＂W＂ shape, which means that the baseflow follows a four-stage sequence of descending-ascending-descending-ascending. As analyzed, the relationship among baseflow, precipitation and temperature is implied in the correlation between their normalized wavelet coefficients at different temporal scales. By the significant positive linear correlations both be- tween precipitation and baseflow （correlation coefficient is 0.98） and between temperature and baseflow （correla- tion coefficient is 0.90） for the 43-year wavelet coefficients, it is suggested that the long-term increasing trends of precipitation and air temperature will lead to an increasing trend of baseflow. For wavelet coefficients of 21-year and 7-year periods, the positive linear correlation between precipitation and baseflow is signi展开更多
Agrometeorological disasters severely impact agriculture in Heilongjiang Province.Flood is one of the main agrometeorological disasters in Heilongjiang Province.The temporal change in flood events in Heilongjiang Prov...Agrometeorological disasters severely impact agriculture in Heilongjiang Province.Flood is one of the main agrometeorological disasters in Heilongjiang Province.The temporal change in flood events in Heilongjiang Province from 1986to 2015 was studied using Mann-Kendall and Morlet wavelet methods,respectively.The results of Mann-Kendall analysis showed that the disaster rates of flood gradually stabilized from 1986 to 2015 with a confidence level of 99%.The Morlet wavelet variance analysis revealed that disaster rates of flood changed periodically at time scales of 3a,7a and 18a in Heilongjiang Province during1986-2015.The dominant period of the variation of flood disaster rate was about 18a over the past 30 years.The flood disaster rates were indicated in a positive phase during the period of 2016-2020 by the fitting curve of Morlet wavelet analysis.The annual average flood disaster indexes of single station,during 1986-2015 years were calculated,according to the precipitation data at 31 stations in Heilongjiang Province and the GIS software was used to analyze the spatial change in flood disasters in Heilongjiang Province from1986-2015.The results demonstrated that the southwest area of Heilongjiang Province was highly hazardous region of flood.The flood indices in the northern part of Songnen Plain and southwest of Heilongjiang Province presented the increment trends.展开更多
基金funded by the China Geological Survey(1212010818093)the National Natural Science Foundation of China(41072191)Foundation of Graduate Student Science and Technology Innovation from China University of Geosciences in Beijing
文摘Baseflow, which represents the drainage of groundwater aquifers, is an essential component of runoff in hydrological basins. In the source region of the Yangtze River, the change of baseflow typically reflects the in- teractions between groundwater system and climatic factors in cold and arid areas. With modified Kalinen separa- tion method, annual baseflow between 1957 and 2009 in this region was estimated and calculated. In comparison with the inner-annual variations of total streamflow, baseflow showed a weaker fluctuation. Before the 1980s, it was in a steady state; and after then, it demonstrated dramatic variations and large amplitudes. Based on the calculation results of baseflow, the real Morlet wavelet method was applied to reveal the periodical characteristics of baseflow as well as the precipitation and air temperature in the study area. It was found that annual baseflow has a 43-year trend as well as a 21-year period and a 7-year period. The 21-year period is most significant, with its wavelet coef- ficient having the largest fluctuation and amplitude. Summation of wavelet coefficients on these periods exhibits a similar change pattern with respect to that of annual baseflow. The summation curve takes a ＂W＂ shape, which means that the baseflow follows a four-stage sequence of descending-ascending-descending-ascending. As analyzed, the relationship among baseflow, precipitation and temperature is implied in the correlation between their normalized wavelet coefficients at different temporal scales. By the significant positive linear correlations both be- tween precipitation and baseflow （correlation coefficient is 0.98） and between temperature and baseflow （correla- tion coefficient is 0.90） for the 43-year wavelet coefficients, it is suggested that the long-term increasing trends of precipitation and air temperature will lead to an increasing trend of baseflow. For wavelet coefficients of 21-year and 7-year periods, the positive linear correlation between precipitation and baseflow is signi
基金Supported by China Clean Development Mechanism Project(2014101)。
文摘Agrometeorological disasters severely impact agriculture in Heilongjiang Province.Flood is one of the main agrometeorological disasters in Heilongjiang Province.The temporal change in flood events in Heilongjiang Province from 1986to 2015 was studied using Mann-Kendall and Morlet wavelet methods,respectively.The results of Mann-Kendall analysis showed that the disaster rates of flood gradually stabilized from 1986 to 2015 with a confidence level of 99%.The Morlet wavelet variance analysis revealed that disaster rates of flood changed periodically at time scales of 3a,7a and 18a in Heilongjiang Province during1986-2015.The dominant period of the variation of flood disaster rate was about 18a over the past 30 years.The flood disaster rates were indicated in a positive phase during the period of 2016-2020 by the fitting curve of Morlet wavelet analysis.The annual average flood disaster indexes of single station,during 1986-2015 years were calculated,according to the precipitation data at 31 stations in Heilongjiang Province and the GIS software was used to analyze the spatial change in flood disasters in Heilongjiang Province from1986-2015.The results demonstrated that the southwest area of Heilongjiang Province was highly hazardous region of flood.The flood indices in the northern part of Songnen Plain and southwest of Heilongjiang Province presented the increment trends.
