长江源头流域水文要素时空变化及对气候因子的响应

摘要

长江源区位于青藏高原腹地,其水文过程空间异质性强、对气候变化敏感,但其水文要素的时空特征尚不太清楚.本文结合站点和同化气象要素资料,采用寒区水文模型(CRHM)模拟了1979—2012年间长江源沱沱河、楚玛尔河和当曲流域的汛期水文过程,据此分析了其汛期水文要素的时空变化特性,解析了水文要素对气候因子的响应.结果表明:(1)沱沱河、楚玛尔河和当曲三子流域的汛期径流深度与系数具有显著的空间差异,依次分别为:56.4 mm和0.20、7.1 mm和0.03、152.0 mm和0.41,呈南多北少的空间规律,与降水分布基本一致;(2)1979—2012年间,长江源区径流深与降水显著相关,表明源区水文过程对降水变化敏感(R>0.54,p<0.01);(3)唐古拉山地区的汛期产流量深明显高于周围地区,并表现出对降水的敏感响应(R>0.95,p<0.01),而当曲流域沼泽湿地则为蒸散发高值区.本研究阐明了长江源头流域汛期水文要素空间特征及时间变化,并表明了水文过程的气候敏感性及其空间差异,这在长江源区的气候变化响应分析中应予以充分考虑.%The source area of the Yangtze River(YR)originates from the Tibetan Plateau,where regional climate warming has been observed over the past half century,leading to growing spatial heterogeneity of hydrological processes in the area.However,researches on the variation of hydrological processes were restricted due to insuffi-cient observations.In this study,the hydrological processes in the source area of YR were investigated using hydro-logical modeling and integrated multiple observations.Using historical data from 1979 to 2012,the hydrological processes of three major sub-basins(i.e.,Tuotuo River(TR),Qumar River(QR)and Dam River(DR))were analyzed by the Cold Region Hydrological Model(CRHM).Then,the spatial-temporal characteristics of the proces-ses and their hydrological responses to climate change were analyzed in different hydrological response units (HRUs).According to the results,the average runoff depth and average runoff coefficient were 56.4 mm and 0.2 in TR,7.1 mm and 0.03 in QR and 152.0 mm and 0.41 in DR sub-basins,respectively.The spatial distribution of the runoff depth and runoff coefficient in each sub-basin as well as the whole region varied distinctly with a decrea-sing trend from south to north.This phenomena demonstrated a moderate agreement to the spatial variation of pre-cipitation over the region(correlation coefficients R>0.54,and statistical significance p<0.01),which revealed the influence of precipitation to hydrological processes in this region.The sensitivity of the modeled hydrological processes in different altitudes was also illustrated by the simulation;runoff depth of the mountain area in the south-west was significantly higher than one in the lowlands,showing high positive correlation against precipitation(R>0.95,p<0.01).In the swamp dominating southeast area,however,much lower runoff depth was obtained due to high evapotranspiration.This study suggested that hydrological responses to climate changes in the source area of YR were strongly related to the spatial heterogeneity in different sub-basins,which should be carefully taken into ac-count in estimating further hydrological variations in this region.