20世紀(jì)后半期,，美國河流水文水資源的變化吸引了很多的研究,，這主要有兩個原因。其一,，這個時期大氣中溫室氣體的濃度有一個顯著升高,，且與之相聯(lián)的水文循環(huán)的加劇吸引了科學(xué)家的注意；另外,，這個時期水文觀測站數(shù)量龐大可以提供充足的數(shù)據(jù)進(jìn)行此類分析,。前人研究發(fā)現(xiàn)，美國河流流量（主要集中在中低流量的徑流）顯著增加,，主要由氣候（降雨）的變化導(dǎo)致的,。但是大多數(shù)研究主要應(yīng)用了HCDN（Hydro-Climate Data Network）數(shù)據(jù)庫，而這個數(shù)據(jù)庫的時段在~1950s-1988,，并不能真正反映20世紀(jì)后半期,。
中科院亞熱帶農(nóng)業(yè)生態(tài)研究所生態(tài)水文組的徐憲立研究員與國內(nèi)外合作者應(yīng)用了另一更能代表這個時期的數(shù)據(jù)庫MOPEX，嚴(yán)格將時段限制在~1950s-2000,，在全美范圍內(nèi)選擇了302個流域的水文氣象數(shù)據(jù),，重新分析了20世紀(jì)后半期美國河流水文過程的變化。他們的研究指出,，20-30%的流域呈現(xiàn)出了產(chǎn)流增加的趨勢,，大多數(shù)（> 65%）流域沒有發(fā)生顯著的變化。而前人基于HCDN數(shù)據(jù)庫的研究指出50%以上的流域產(chǎn)流增加的趨勢明顯,。與前人研究相似,，他們的研究也發(fā)現(xiàn)河流徑流和基流的增加主要發(fā)生在美國的中西部和中北部。基于氣候敏感性分析指出氣候變化（變異）對河流徑流的變化貢獻(xiàn)要大于人類活動（61±25 % vs. 39±25 %）,，但是對河流基流的變化的貢獻(xiàn)略低于人類活動（49±26 % vs. 51±26 %）所引起的變化,。運(yùn)用突變點(diǎn)探測技術(shù)分析發(fā)現(xiàn)，35-45%的流域在1971年左右河流徑流和基流發(fā)生了階躍性變化,。
他們的研究為美國20世紀(jì)后半期的水文變化及其歸因的分析提供了新的視角,，同時表明數(shù)據(jù)尤其數(shù)據(jù)時段的選擇對分析水文變化及其歸因有較大影響。（生物谷Bioon.com）
生物谷推薦的英文摘要
Water Resources Management doi:10.1007/s11269-013-0411-3
Revisiting Continental U.S. Hydrologic Change in the Latter Half of the 20th Century
Xianli Xu,， Wen Liu,， Rashad Rafique， Kelin Wang
An intensified hydrologic cycle and a large amount of monitoring flow data in the latter half of the 20th century attracted a lot of research on the continental U.S. hydrologic change. However,， most previous studies are based on HCDN (Hydro-Climate Data Network) dataset with a period of ~1950s -1988. This study analyzed hydrologic change in continental U.S. based on MOPEX (international Model Parameter Estimation Experiment) hydrology dataset with a period of ~1950s -2000 for 302 watersheds (gages) across diverse climate,， vegetation and soil conditions. This dataset is more representative of the latter half of the 20th century than HCDN. In contrast with previous studies， this study shows that only 20–30 % of watersheds present increasing trends in flow (streamflow,， Q,； baseflow， Qbf,； baseflow index,， BFI)， and most (> 65 %) watersheds presents non-significant trends. Similar to previous studies,， the watersheds with increasing trends in Q and Qbf are concentrated in Midwest and high plain (North-Central area) of USA. Climate contributes more to Q change (61±25 % vs. 39±25 %) but slightly less to Qbf change than human activity (49±26 % vs. 51±26 %) and much less to BFI change than human activity (5±61 % vs. 105±61 %). A step change at ~1971 in Q and Qbf was found for 35–45 % but not for a large proportion of watersheds (50 % or more was reported by previous studies). This study provides new insights on the latter half of the 20th century’s hydrologic cycle for the continental U.S. with a more representative dataset of this period.
