1.1+Hydrological+cycle

1. What is the hydrological cycle and how does it work? [Hydrological cycle is the water cycle with knobs on!] You will have come across the water cycle before. The **hydrological cycle** has a bit more to it. This is not a perfect diagram but I can’t draw so it will have to do! We define it as a **closed system** because it goes round and round and nothing can be added and nothing can be taken away. It also has several more words added, and a couple more ideas besides. Let’s look at the words: (a) The water, from various sources, but mainly the sea, is heated by the sun and some will **evaporate**. (b) The warm air carrying the water vapour rises up, where it cools as it gets further from the earth’s surface. (c) The vapour begins to **condense** into tiny drops of water and form clouds. Some of these will be blown over the land. This forces them up higher, causing more cooling, and the drops coalesce to get bigger, cutting out more sunlight so the clouds appear dark. (d) The larger drops are now **precipitated** from the cloud falling as snow or rain, depending on the height of the land they fall on. (e) If the rain lands on soil, it may run down hill over the surface (**surface run-off**) and into a river or it may soak into the soil (**infiltration**) or it hang around as puddle for a while (**surface storage**) before evaporating or it may soak into the ground by **infiltration** (g) If it is caught up in trees and plants we say it in **intercepted**. It may just slow up its route to the ground as much of it will soon drip off the leaves and end up on the soil (**throughfall stemflow**) But some may stay trapped in the vegetation for quite a while.**(vegetation storage, if only temporary)** (h) Some may fall straight into the river and be carried back to the sea (**stream flow**) or into lake.(yet another form of **surface storage).** (i) For the water that infiltrated into the soil, some might stay there for a while (**soil storage**)some will taken up by plants but some will flow down hill through the soil (**through flow**) and some will soak down into cracks in the rocks beneath the soil (**percolation**). It can stay there for some time (**groundwater storage**) or main run out as a spring. (j) Once all the spaces in the rock are filled, it is **saturated** and water may stay there for years as ground **water storage**. Then the water getting that far has reached the **water table** it will flow down hill as **groundwater flow**. With a couple of exception, the above is about water moving from one place to another – so all these processes are called **flows.** However, as was mentioned, the water may stay in one place for a shorter or longer time – these are called **stores**. Revision of drainage basin words **
 * (f)** If the precipitation lands on a mountain top as snow, it may well hang around in the glacier for sometime, another form of **surface storage**


 * < === What do you need to remember? === ||
 * < * All the words in BOLD
 * Know which are stores and which are flows ||