Water Balance
The water balance lesson, was not really the best lesson as there was no Mr. Heah :'(... anyway, The lesson taught us that the water that comes from the environment MUST go somewhere and cannot just disappear. It was given by the equation P = (change in S) + E + runoff [cant remember the variables. trying my best to recall what was taught without the help from the notes :D.
So, P = precipitation, change in S = change in the storage amount in the soil, E = evapotranspiration which is known as evaporation + transpiration and finally runoff meaning the amount of water that was not absorbed by the soil being flowed away to a water body like a river or a lake.
So we were given some situations:
1) Cloud Seeding
2) Damming
3) Agriculture
4) Urbanization
5) Grazing
Basically, we just have to determine what factors were affected due to these 5 activities, resulting in a change in the constants. :D
Thats about it
Choo Wen Yi
posted by 08ip01 at
6:19 PM
6 Comments:
Human activities sure are affecting the balance of the systems on earth. Just by urbanization, we affected both the water balance and the atmosphere.
It's quite a sad thing that while we were given the ability to do things that other life forms are unable to, we ended up using it in a manner that upsets the balance of nature and causing mother earth to get hurt as a result of our actions.
Actually, the idea of water balance can be easily understood in this way: Water must be conserved since only physical processes are considered, hence for whatever amount of water precipitated (P) there must be the same amount of water that either (1) Evaporate back to the atmosphere - E (2) Run away - Q or (3) being stored somewhere - delta S.
Take note that the water balance holds true if chemical processes involving water such as photosynthesis are neglected. In fact, if the amount of precipitation is small and the land is heavily vegetated then the water balance may not hold true since the amount of water chemically changed by plants is not negligible compared to other factors.
Now I'll elaborate more on how those human activities affect water balance:
1. Cloud seeding actually increases the amount of precipitation. On the other side of the equation, as long as the soil is not saturated yet, delta S will still keep increasing till the point where the soil is saturated. Since then, extra precipitation will indeed go into run off (Q).
2. Damming is actually increase the storage.
3. Assume that the considered piece of land was a hill covered by concentrated forest. Being replaced by other plants such as corn or rice, "interception capacity" of the vegetation layer will drop. Subsequently, the soft and spongy soil on top of the land will be more likely to washed away since less interception occurs. Since storage capacity of the soil and evapotranspiration drop, run off increases.
Following the similar steps, 4 and 5 can be done easily.
WHO WROTE THIS POST? YOU DID NOT WRITE YOUR NAME!!!
It actually sounds a bit like energy in that the input must always equal the output and nothing is lost. And perhaps the post could have been a bit longer...by the way, Nurul, I think this post is Wenyi's
1.Cloud seeding leads to increase in precipitation as they are more clouds so they trap more moisture so there is more rain
2. Damming leads to increase in evaporation as more water is exposed to atmosphere
3. Agriculture increases S as infiltration capacity of water increases because water being soaked by ground is taken by Crops.
4.Urbanization leads to floods because of decrease in S and there may also be increase in evaporation because water may be stored on the top of buildings.
5. grazing leads to increase in evaporation and decrease in S as the plants have been grazed by COWS or other animals
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