Global characteristics of stream flow seasonality and variability

Monthly stream flow series from 1345 sites around the world are used to cha racterize geographic differences in the seasonality and year-to-year variab ility of stream how. Stream flow seasonality varies regionally, depending o n the timing of maximum precipitation, evapotranspiration, and contribution s from snow and ice. Lags between peaks of precipitation and stream flow va ry smoothly from long delays in high-latitude and mountainous regions to sh ort delays in the warmest sectors. Stream flow is most variable from year t o year in dry regions of the southwest United States and Mexico, the Sahel, and southern continents, and it varies more (relatively) than precipitatio n in the same regions. Tropical rivers have the steadiest hows. El Nino var iations are correlated with stream flow in many parts of the Americas, Euro pe, and Australia. Many stream flow series from North America, Europe, and the Tropics reflect North Pacific climate, whereas series from the eastern United States, Europe, and tropical South America and Africa reflect North Atlantic climate variations.