تحميل كتاب Isotope Hydrology pdf 2005م - 1443هـ نبذه عن الكتاب: “Water, water, every where, — nor any drop to drink” (Samuel Taylor Coleridge, “The Rime of the Ancient Mariner”) aptly sums up the overall picture of the hydrosphere — that part of planet Earth made up of water. The oceans, covering 71% of the surface of the globe, make up 97.25% of the mass of water. Most of the freshwaters, whose volume is estimated to be 39·106 km3, are also not immediately accessible: 29·106 km3 is ice accumulated on mountain glaciers and on the ice caps of the poles; 9.5·106 km3 constitute groundwaters and only about 0.13·106 km3 are surface waters, mainly lakes and rivers. The amount of water held up in the biosphere is estimated to be 0.6·103 km3. The atmospheric moisture amounts to just 13·103 km3 — less than 10−5 of the total amount of water — but this small amount is the one which actuates the hydrologic cycle by virtue of its dynamic nature. Figure 1.1 shows in a schematic fashion the components of the hydrologic system and the mean annual fluxes between these compartments, i.e. the evaporation, transport through the atmosphere, precipitation over sea and land surfaces, and the backflow to the ocean as surface and sub-surface runoff. Some secondary loops of water recycling from the continents to the atmosphere are also indicated. It is evident that to a first approximation, the hydrologic cycle is a closed one. However, the different reservoirs are not strictly in a steady state, on a variety of time scales. There is a marked seasonal imbalance caused by snow accumulations on large land areas in winter; soil moisture and surface reservoirs such as lakes and wetlands fill up during rainy periods .
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