降雨与土地覆盖对中国典型流域水文干旱的影响分析

Effects of Precipitation and Land Cover on Hydrological Drought in Typical Basins of China

水文干旱严重制约了我国社会经济的发展。在气候变化和人类活动的影响下,水文干旱频繁发生,导致流域水资源短缺问题更加突出,因此,需从多因素角度分析不同因素对水文干旱的影响,从而为流域抗旱提供参考。为此,选取中国用水矛盾突出,旱灾较为严重的典型流域——湘江和渭河流域为研究区域,探究降雨特征与土地覆盖的变化对两地水文干旱的影响。首先,通过Pettitt突变检验法与降雨-径流双累积曲线法确定两个流域径流突变点,根据标准化径流指数识别了径流突变点前后湘江、渭河流域的水文干旱事件,最后基于随机森林与线性回归方法对比分析两地不同时期内降雨特征与土地覆盖的变化对水文干旱的影响。结果表明:湘江流域径流在1982-2015年间未发生突变,降雨特征是影响湘江流域干旱的主要因素,贡献率为53.4%,其中降雨量的贡献率为33.25%,比降雨集中度的贡献率高出13.1%,而土地覆盖的变化对湘江流域水文干旱影响不显著,其对水文干旱的贡献率仅为36.6%。渭河流域径流在1993年及2003年发生突变,不同时段内流域水文干旱的主要影响因素各异:1982-1993年间,影响当地水文干旱的主导因素为降雨量,其贡献率为34.4%;降雨特征与土地覆盖对干旱的贡献率在1994-2003年间持平;而在2004-2015年间,森林覆盖率的变化成为影响流域干旱主要因素,其贡献率为40%。基于研究结果,水利管理部门可根据当地流域的气候条件、土地覆盖类型,有针对性地制定防旱措施。

Hydrological drought has seriously constrained the socio-economic development of China.Under the influence of climate change and human activities,hydrological droughts occur frequently,leading to the more prominent problem of water shortage in basins.Therefore,it is necessary to analyze the influence of different factors on hydrological droughts from a multi-factorial perspective,so as to provide a reference for drought relief in basins.To this end,the Xiangjiang and Weihe basins,which are typical basins in China with prominent water use conflicts and severe droughts,were selected as the study areas to investigate the effects of precipitation characteristics and land cover changes on hydrological droughts in the two basins.Firstly,the Pettitt mutation test and the rainfall-runoff double cumulative curve method were used to determine mutation points of streamflow in the two basins,and the hydrological drought events in the Xiangjiang and Weihe basins before and after the mutation points were identified according to standardized streamflow index.Finally,the impacts of changes in precipitation characteristics and land cover on hydrological droughts in two basins during different periods of time were analyzed based on the comparison of the random forest and linear regression methods.The results indicate that the runoff in the Xiangjiang River Basin did not change suddenly between 1982 and 2015.The precipitation characteristics are the main factors influencing hydrological drought in the Xiangjiang basin,contributing to 53.4% of hydrological drought,with precipitation amount contributing 33.25%,which is 13.1% higher than the contribution of precipitation concentration.However,changes in land cover have no significant effects on hydrological drought in this basin,with a contribution rate of only 36.6%.The streamflow of the Weihe basin experienced sudden changes in 1993 and 2003,and the main influencing factors of hydrological drought in the basin were different in different time periods.During the period of 1982-1993,the dominant factor influencing the intensity of the local hydrological drought was precipitation amount,with a contribution rate of 34.4%.The contribution of precipitation characteristics and land cover to drought was equal during 1994-2003,while changes in forest cover became the main factor influencing drought in the Weihe basin during 2004-2015,with a contribution rate of 40%.Based on the research results,water management authorities can tailor drought preparedness measures to the climatic conditions and land cover of local basins.