The hydrological cycle
Issue No. 5 of Schlossplatz3, to appear in September 2008, will focus on “water”. To prepare the ground, Diana Dus, alumna from HSoG’s class of 2007, illuminates the prized and contested liquid from various perspectives. This time, she focuses on the hydrological cycle.
Using the thermal energy of the sun, water evaporates from the surface of the oceans, lakes and rivers. Since the gaseous water particles do not carry salt or any contaminants, this first step is both a desalinizing and purifying process. The clean water vapors attach to dust, sea salt crystals or bacteria forming droplets of water, which create different shapes of clouds and travel towards land, where, due to changes in pressure, they discharge and fall in form of rain, sleet, hail or snow. It is then gathered in lakes and rivers and transported towards the ocean.
There are other participants, namely plants and soil that contribute to this cycle. Plants also transpire some water into the athmosphere, and they have a significant role in keeping water in the soil. Through the system of their roots, the earth is able to retain more water, slowly recharging underground containers, called aquifers. Thus, water can stay underground, sometimes for thousands of years, before surfacing again.
Human activities in many points intersect with this cycle. Just to name a few from the many examples: air pollution creates acid rain from the otherwise pure water particles; cutting down forests leads to soil erosion and possible desertification, cities and constructed structures prevent water from recharging groundwater, and lead to greater runoff. These and other activities not only alter the quality, but also have some enormous effects on the quantity of water we receive.


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