31 March 09
In this lesson, the water balance P= E + Q +∆ S, as well as several other factors involved were taught.
Precipitation is measured by the summation of the level of Evapotranspiration (E) summed with the Runoff (Q) and rate of change in the levels of the initial Soil moisture and final soil moisture.
The water balance is usually used by hydrologists to plan and manage water supply within a drainage basin. It can be applied to predict possible water shortages, irrigation patterns, pollution control and flooding.
Additional factors that are involved with Infiltration were also discussed, with Interception by vegetation being the concentration of the discussion. Most drainage basins are clothed by one or more forms of vegetation. This vegetation will to some extent intercept precipitation. Water may be held on the leaves to then be evaporated or flow down from leaf to leaf as throughfall. It may also flow down from tree trunks or plant stems as stemflow.
Vegetation also reduces rainsplash, by absorbing the impact of raindrops by preventing them from landing directly on the ground. This reduces soil erosion and soil compaction (which may encourage overland flow.) Plants also reduce the amount of water available in the system by the use of water as they grow (absorption of water through roots). Its rate of transfer is also slowed as the roots encourage water to pass into the soil and rock.
Another item discussed was the possible variations to the equation by human activity, mainly by deforestation or reforestation. If P stays the same, and E becomes more (more trees), S decreases. If P stays the same, and E decreases (less trees), Q would become more. S does not necessarily increase as there would be rivalling factors involved such as, less absorption yet more rainsplash.etc.
CHESTER LAU jh40614
Yaaay! Finally a new post! Thanks Chester! :)Keep it up guys! Blogging is a great way to consolidate your thoughts...How about the previous lesson on drainage basins??
ReplyDeletewow! this equation really explains a lot of things. it really helps us to understand the water cycle better!
ReplyDeletejia min 406
hey!i think urbanisation is also a very important factor. more countreis these days are transforming agricultural land into urban lands where concrete and buildings take over soil and trees. Also, to prevent flooding, urban areas usually have an extensive system of drainage system. they build drains which facilitate over land flow. moreover, concrete is impermeable.therefore, more overland flow is created!hence discharge would increase, lag time will be shorter and peak will be higher!(:
ReplyDeleteJIAYI!
Yup I agree with Jiayi, as urbanisation is much more relevant to us in the modern world today. Grazing can't be ignored too though, as in the modern world, grazing is still commonly found, and is causing more overland flow in the rivers. This water balance equation really helps us understand and equate out information that we might want to know accurately.
ReplyDeleteLuke