Standard Article

197 Observed Trends in Hydrologic Cycle Components

Part 17. Climate Change

  1. Harry F Lins

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa207

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Lins, H. F. 2006. Observed Trends in Hydrologic Cycle Components. Encyclopedia of Hydrological Sciences. 17:197.

Author Information

  1. United States Geological Survey, Office of Ground Water, Reston, VA, US

Publication History

  1. Published Online: 15 APR 2006

Abstract

Documentation of change in the Earth's climate is accomplished by assessing the rates, magnitude, and distribution of changes in various elements of the climate system, such as the components of the hydrologic cycle. The present section reviews the general character of changes in precipitation, streamflow, and evaporation as determined using systematically collected data through the end of the twentieth century. Precipitation over global land areas increased about 2% during the century, and streamflow also exhibited widespread increases. There was good agreement regionally between the observed precipitation and streamflow increases. The precipitation increases appear to have occurred most commonly in higher intensity categories (>50 mm per day), while the streamflow increases were overwhelmingly observed in the low to moderate range of flows. No systematic increases were observed in peak streamflows. These findings indicate that a general intensification of the hydrologic cycle occurred during the twentieth century, but that this intensification did not result in increased hydrologic extremes.

Keywords:

  • evaporation;
  • hydrologic cycle;
  • precipitation;
  • streamflow;
  • trends