Hi everyone,

From today’s lesion, we were continuing to discuss about the drainage basin which is an essential part of hydrological cycle. To help us have a better understanding of it, we were brought downstairs behind TC block to see how the whole system looks like. By definition, a drainage basin is not only a river. Instead, it is the area that is drained by a main river and its tributaries. Those tributaries are always from higher altitude because water flows down due to the gravity by the earth. They contribute to the main river.

However, drainage basin is not only the water-flow. It refers to the area that is drained. Those areas are always covered by vegetation. Water does not flow very fast because of the existence of vegetation and soil.
Vegetation reduces the rate of the entire hydrological cycle because IT CAN STORE WATER. Hence less (Slower rate of the hydrological cycle is not the same as less water in the system) water will flow into the system. Different vegetation will result in different interception of water. Those huge rainforest will store more water than grass.

Vegetation also prevent the lost(loss) of soil. When soil is saturated, the excess water will bring the soil the river. It causes the lost of soil and an increasing level of river. Vegetation will store the excess water and hold the soil more tightened. Another factor that affects soil moisture is temperature. During summer, high sunlight density and higher temperature will let soil evaporate more water while water tends to remain during winter. (Are you sure?)

So far, we have discussed about the drainage basin and its river and how the vegetation zone store water. But why is water so important?

The main idea is that life needs a LIQUID MEDIUM to transporting the molecules that are necessary for its existence. Water is the main liquid in the earth.

How does water’s property help remain lives? The key is to understand the structure of water-------hydrogen bonding. Firstly, it becomes less dense as it freezes. It allows the ice float up to block the cold temperature from air keep freezing the water. Aquatic life hence can survive during cold weather. Secondly, it allows water to remain liquid state over a large range of temperature. That means it will not change its property of conducting molecule transporting easily(Liquids transport molecules far more effectively than Solids or Gases. Water stays as a liquid over a wide range of temperature). Thirdly, it makes water have high specific heat. It allows water remain in a stable range of temperature even absorbing a large amount of energy(Back to the question, water helps keep the body temperature constant). Furthermore, hydrogen bonding plays the role in reproducing and evolving life. It helps the 2 DNA strands bond together.

Nonetheless, water also other characters also helps maintaining life on Earth. It can dissolve materials (Chemicals? Compounds?) to assist in transporting molecules. The clouds also help block out harmful UV light. ( Ozone layer does, Clouds and dust only absorb heat)

Just a short revising,

Drainage basin contains 2 parts: River and its tributaries, the area drained.
The importance of vegetation zone: containing water (Should be reducing overlandflow by delaying the water flow and providing another pathway for water which is transpiration)
The importance of water: Hydrogen-bond (high specific heat(How do you know that H bond is responsible for it since H bond is not a strong bond?), large temperature range, DNA bonding) and other characters (perfect solvent, UV light blocker (Water never blocks UV light =.=), etc)

Comments made by Minh.
Lignum Rocks.

Cai Yida/27 March

Aditya

Hi all,

      On Tuesday we had our lesson near the fish pond where Mr. Heah taught us about the drainage basin. In the previous lessons we had about learnt the basic water cycle. Water evaporates from the water bodies, rises, expands and cools. Then the clouds get heavy and water droplets fall from sky as raindrops.

      So, when a water droplet  falls what can happen to it?--

1.   So when the water droplet falls it reaches the ground surface and is soaked by the soil (Infiltration).  The Infiltration capacity is the rate at which water soaks into the soil. If the amount of water received by the ground exceeds the capacity of the soil, this leads to collection of water on the surface. This is what we saw on the backside of staff room.

2.    The water droplet can flow down the slope laterally. (throughflow)

3.    The water droplets may flow laterally horizontally (baseflow)

4.    It may fall on the trees and leaves (interception). Tree by itself acts like an inverted drainage system.

5.    The water droplets that fall on the leaf may be evaporated or it may drop down from leaf (Through fall)

6.    The water droplets may flow down the stem of the tree.(stemflow)

If we change the ground from soil to concrete then it can affects the drainage system and the water reaching the ground will decrease. This will severely affects the amount of groundwater and the water available to the plants.

Thank You.

Zhang Wanying

Hello!
Today we started our lesson with a question: what did the rain come from last night? We were split into groups to discuss the question. So basically, the answer is, there are monsoon seasons happening twice each year in Singapore. The first one is the Northeast Monsoon which occurs from December to early March. The second is the Southeast Monsoon season which occurs from June to September. So now we are in the Northeast Monsoon. During the Northeast Monsoon, the place that receives the most amount of sunlight moves from the tropic of Capricorn to the equator. As a result, air of north part of the earth is cool and it sinks; air of south part of the earth is hot and it rises. The air moves up and down between tropic of cancer and tropic of Capricorn. Because of coriolis force which is due to earth’s rotation, air moves in this way:

The wind comes from northeast (so the wind is called ‘northeast wind’) of Singapore. As we can see on the map, the arrows indicate the direction of the wind. As a result, the wind brought the moisture of the South China Sea to Singapore. That’s why it was raining heavily last night.

From June to September is the Southeast Monsoon season. The place that receives the most amount of sunlight moves from the tropic of cancer to the equator. Hence air of north part of the earth is hot and the air of south part of the earth is cool, and air moves from south to the north. The air comes from Indian Ocean towards Singapore. Because of the unequal heating of land and sea, the air flows in the direction shown in the map below. However, there is an island with volcanoes called Sumatra blocking the air from Indian Ocean to Singapore. Hence, from June to September, Singapore is relatively dry. However, there is still convectional rain. It still get low amount of rainfall.

I guess that's all for today.

All the best for our assessment week. :)

Zhao Pei

HELLO! HELLO! :)
So it is finally my turn to blog! Minh and Yida are absent both today. They are roommates of each other. I can not image what they were doing in their room while we were having Geo lessons...
Haha. Sorry for being so random. Today we talked a lot about the SEASONS and the DESERT. I think Minh had talked a lot about the seasons in his previous blog. So I shall focus on desert today:)
We are in the DESERT now! If you look at the world map carefully, you will notice that most deserts do not distribute among the equator. Places at the equator receive more sunlight and radiation than other places in the world. But why deserts are not found in equator?
Before we answer that question, we shall focus on the following two questions: "how does the air move around the earth? " and "how does gas transfer the heat? "
You can draw a diagram to show how the air move around the earth. And this is our answer :D

HOWEVER, all of us forget that the world we live in is 3D! But never mind, the teacher said we grabbed the concept already! :)
We shall take notice that warm air does not transfer forever, it will sink/rise once it gets cool/warm.
So here is correct version:

It is the same with this diagram below:

And we shall not forget that the earth will rotate from the west to the east. Therefore:

(I think I drew too many diagrams today and I hope they are useful.)
Last Question: Why desert are not found in the equator?
-What define deserts? What made deserts? (Dry! Lack of water→desert!!! Desert depends on amount of precipitation, not heat. )
Because ,the air is cooled down and therefore the air sinks at the hemispheres. (Which means there is no adiabetic cooling and air there will never rise.) Therefore there is very little precipitation around those areas. That is why you can see clear blue sky in the desert in the day time. Because there is no cloud covering, the temperature of desert is very high in the day time(40̊ C-50̊ C) and id very low at night (around-10̊ C).
So, that is about it, I hope:)

Comments:

Just to add on, I believe that the global air circulation is also one of the reasons why we

experience a tropical climate at the equator. For the presence of precipitation, there has to be adiabatic cooling. If we observe the 3-cell model, we notice that the Hadley cell, fuelled by heat from the sun, gives rise to rising air from the equator. Consequently, precipitation is greatest around the equator and gives us our tropical climate.

Similarly, as precipitation is the least where air descends, deserts also occur at the poles where the cool air sinks. As there is no precipitation, this polar deserts experience little snow, yet due to their location on the Earth, they still experience the cold climate unique to the poles. Its kinda cool actually :)

Victoria