The surface-water components of the hydrologic cycle usually are considered to be rainfall and subsequent runoff. Yet, in many parts of North America, for a major part of the year, the more appropriate concept is precipitation and storage as snow and ice, followed by melting, followed by runoff. The timing involved in these two concepts is very different: Runoff follows rainfall almost immediately, whereas the time between snowfall and melt can range from days to months for seasonal snowcovers, and from months to millennia for glaciers. The predictive analysis of runoff also is very different: Prediction of runoff from rainfall requires knowledge of the precipitation pattern in time and space, whereas the prediction of runoff from snow and ice melt requires knowledge of the amount and distribution of snow in storage (measurable), and the meteorologic conditions that cause melt. The fact that snow and ice accumulate and melt to produce runoff in a very different way than does rainfall commonly is ignored in a simple hydrologic analysis.
Figures & Tables
Surface Water Hydrology
Provides reviews of all major facets of hydrology. Topics covered include: influences of the atmosphere and of land and vegetation on stream flow; temporal and spatial variability of stream flow, with separate chapters on floods and on low flow and hydrologic drought; snow and ice, the frozen components of the hydrosphere; the hydrology of lakes and wetlands; hydrogeochemistry of rivers and lakes; the aquatic biota; sediment movement and storage; the riverscape for selected North American rivers; and the influence of Man on hydrologic systems. Accompanying color plates show histograms of river water chemistry, runoff and flow regimes, and the distribution of precipitation minus evaporation for North America.