Standard Article

175 Observations of the Global Water Cycle – Global Monitoring Networks

Part 15. Global Hydrology

  1. Dennis P Lettenmaier

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa181

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Lettenmaier, D. P. 2006. Observations of the Global Water Cycle – Global Monitoring Networks. Encyclopedia of Hydrological Sciences. 15:175.

Author Information

  1. University of Washington, Department of Civil and Environmental Engineering, Seattle, WA, US

Publication History

  1. Published Online: 15 APR 2006


Until the last few decades, in situ networks were the primary source of information for the estimation of the global water cycle. Such networks provide reasonably good climatological estimates of the major terms in the water cycle over the industrialized parts of the world, but are much less adequate in the lesser-developed countries and in sparsely populated areas. Furthermore, in situ networks have been in the decline over the last several decades. An ongoing trend is toward greater reliance on satellite remote sensing. In some cases (e.g. soil moisture), satellite estimates have characteristics that cannot reasonably be matched by in situ networks. In others, it is less likely that the needs for global observations can be met from remote sensing. Furthermore, there will remain a need for high quality in situ data for algorithm testing and evaluation, and for evaluation of differences between historic in situ-based, and satellite-based, observations. The characteristics of in situ and satellite-based estimates of the dominant fluxes and storages in the land surface and atmospheric branches of the global water cycle are reviewed.


  • global water cycle;
  • global water balance;
  • global hydrology;
  • continental hydrology;
  • global precipitation;
  • hydrologic networks;
  • hydrologic remote sensing