Causes of change in 20th century global river discharge

Abstract

A global vegetation and hydrology model (LPJmL) was applied to quantify the contributions of changing precipitation, temperature, atmospheric CO 2 content, land use and irrigation to worldwide trends in 20th century river discharge (Q). Consistently with observations, Q decreased in parts of Africa, central/southern Asia and south‐eastern Europe, and increased especially in parts of North America and western Asia. Based on the CRU TS2.1 climatology, total global Q rose over 1901–2002 (trend, 30.8 km 3 a −2 , equaling 7.7%), due primarily to increasing precipitation (individual effect, +24.7 km 3 a −2 ). Global warming (−3.1), rising CO 2 (+4.4), land cover changes (+5.9) and irrigation (−1.1) also had discernible effects. However, sign and magnitude of trends exhibited pronounced decadal variability and differed among precipitation forcing datasets. Since recent trends in these and other drivers of Q are mainly anthropogenic, we conclude that humans exert an increasing influence on the global water cycle.