Water Features! 5th May ’09

This was Ms Tang’s second last lesson with us, and it was the one of the few times when I actually paid extra attention to the lesson, partly due to the fact that I had to do this blog post. However, I found this lesson rather interesting, when we learnt about waterfalls and rapids. This was what we learnt…

The formation of waterfalls: As water flows over the bedrock, the less resistant (‘soft’) rocks erode first. As the less resistant rocks keeps eroding, the gradient of the slope gets steeper, thus the formation of waterfalls. There is usually a plunge pool at the end of the waterfall, due to the force of the water hitting the bottom.

The retreat of waterfalls: Eventually, the more resistant (‘hard’) rocks will start to erode, thus the gradient gets less steep. However, the main cause of the retreat of waterfalls is the collapsing of the overhanging hard rock due to the erosion of the soft rock.







The formation of rapids is almost similar to that of a waterfall. The ground consists of alternate layers of ‘hard’ and ‘soft’ rocks, with the ‘soft’ rocks eroding first, thus forming a ‘step-like’ structure that resembles a mini waterfall.



Reflections:

Learning about the formation of these natural wonders is rather interesting. It seems so well planned yet it is a natural process, thus I enjoyed the lesson thoroughly (it’s my first time complimenting on Geography). Lesson was as usual, in a hot and stuffy classroom, everyone was noisy while the two groups were presenting on their respective topics. I finally realized that geography is actually a subject which ‘makes sense’. For instance, the steeper a slope of the waterfall, the faster/more the water flows, thus the formation of a waterfall…etc.

-Kevin (finally...)

2 May 2009

Hi 04, let’s revise what we have learnt from the previous lessons.\



*Three types of load:



*Erosion processes:
Corrasion (abrasion): the current picks up materials and rubs them along its banks and bed  the river erodes both horizontally and vertically
Attrition: The rocks collide with each others and break into smaller pieces, and become more rounded
Solution (corrosion): The word solution is used for both transportation and erosion process, but their meanings are slightly different. Solution in transportation means that the substances are just in the water, no chemical change; whereas when we talk about solution in erosion process, they will not be the same. (e.g. in the booklet: “Water contains dissolved CO2 from the air and this may react with limestone and chalk, causing it to dissolve).
Hydraulic action: the sheer force of water pushes into cracks at the river bank and the bank will gradually collapse

* Hjulstrom curve: a graph which shows the relationship between current velocity and particle size

The first line is the critical erosion velocity line: minimum current velocity before the particles are eroded.
The second line is the critical deposition velocity: minimum current velocity before the particles are transported.
Generally, when bigger the particle, the greater velocity needed to pick it up (transport) or erode. Very small and light substances like clay are very easily carried along by the current. However, because the clay particles tend to stick together, it requires higher velocity for the particles to be eroded.

Reflection:
As we gained more knowledge about Geography, I think that we are learning more of the “what” than the “how”. The knowledge in physical Geography is not so hard to get, since we are just accepting everything as fact. I feel like we are trying to make sense of common senses, in a more logical way, and ‘simpler’ way. At the basic knowledge of physical geography, the scientists mainly worked on putting our common knowledge from nature in to a neater and more organized table, for us to see the connection between them, and then make up even more connections (which we need to do ourselves).
I think that most of us would find it kind of boring to keep learning the “what” for so long. However, if we can link the knowledge together in a big picture, it would feel like using Lego to build a model of our nature, with more and more pieces after each lesson :).
I agree with Tung that ‘how’ is more important than ‘what’ (even though he was talking about different things anyway). However, ‘what’ is fundamental. If we don’t know what the problem is, it will be very hard to figure out how to solve the problem.
So, for the time being, let's enjoy Lego! :)

By the way, as I searched the internet, I found this website which contains a lot of useful presentation slides that we can use for our references:
http://www.slideshare.net/maliadamit/river-presentation-presentation (it has a mind map at the start, linking the river processes to different landforms, and then presents the knowledge accordingly)
http://www.slideshare.net/jacksonthree/river-processes-and-landforms (very long slides and I don’t really get the flow of the presentation, but I found it interesting because it has a lot of pictures in real life)
There are also similar slides in the website, hope you find this useful.
And enjoy the rest of weekend!!!
Jenny

RIVERS!

Hello guys!I am really sorry for putting up this post late-.-||. Anyway, thank God, Guzheng SYF is finished!Hooray!XD
OK,let's do some revision. Do you still remember what we learnt on 17th of April?

1. River---Man and civilisation
River is so essential for human development. And learning about the essential living conditions for humans is also important for us. We find out that great civilizations have always flourished alongside rivers. For example, the Yellow River Valley, is always thought to be the cradle of The Chinese civilization. And the Nile River valley in Egypt was the site of the world's first great civilization. Our pretty teacher Ms. Tang also showed us a picture of Nile Delta (which is screenshoted from her favourate Google Earth), and we saw that there is a very high population density along the river but few people live elsewhere in that region.

The explanation is as simple as this:
River-->water necessary for farming & drinking--> better living conditions--> more people live and multiply along rivers.



2. Model-making Time
The second half of the lesson was used for model making activities. We were supposed to make models of deltas, waterfalls, floodplain and levees, meanders,rapids and ox-box lake with plasticine and put them in order according to how a river flows. I feel that this kind of hands on acitivities really helps in understanding. I can have a clear picture of how different parts of a river look like and why they are located at where they are.
Yeah this is the whole model done by Loulou,Jenny,Binghui and YIXUAN!



Before making a model like ours, you must understands what the different parts of the river are.:)By the way, Ms Tang showed us the photos of the waterfalls she took in U.S.,and those photos are cool!:)

OK, lastly, let me ask you a question that we have already discussed in class:
Is the speed of the water in the upper cause always the fastest?Why?


Done by:

GEO-PRESENTATION by YINGZHENG.-

Today’s lesson was a short lesson, but we did learn many important things. Firstly, we learnt in previous lessons about the equation regarding the hydrological cycle. The individual factors that can change are precipitation, evapotranspiration, total streamflow, and also change in soil water storage. These things alone, when changed, will affect our water cycle. We also looked into things like storm hydrographs and rainfall. Different groups took turns to present on the different factors which affected rainfall and such. This was different from an ordinary lesson as it was actually our classmates teaching us. It was very interactive as we asked many questions and clarified many doubts. We were also able to visualize better as there were drawings to aid us.
What we learnt today was mainly about the various factors that affect the hydrological cycle, and why they do. This was then referenced to the smaller factors that defined the water cycle. One factor that affected the activity of the hydrological cycle was afforestation and deforestation. Using the equation we learnt previously, during afforestation, runoff decreases, evapotranspiration increases, and soil water storage decreases. This is because there are more trees, there is an increase in interception, thus there will be less runoff. More tress would then also lead to higher evapotranspiration rates, and their roots, taking up space in the soil, will decrease the soils water storage capacity.
Another change in surrounding was deforestation. Deforestation is actually the exact opposite of afforestation. During deforestation, the number of trees decreases thus resulting in less interception, and more runoff. Similarly, less trees would result in less evapotranspiration, and the lower amount of roots in the soil would then increase its water storage capacity.
Next, there’s agriculture. Agriculture is the growth of vegetation. And as such, infiltration decreases, stemflow and root absorption increases and blocked surface area also increases, thus, throughflow and baseflow would decrease.
The last point presented was grazing. Grazing reduces the amount of vegetation, thus increasing infiltration. This would then result in an exact opposite of agriculture, therefore increasing total throughflow and baseflow.



---YINGZHENG

As we advance in our learning, I realized that we go more and more indebt into things. For Geography, I always thought that the water cycle was simply just the evaporation of water, formation of clouds, then rain. Although this still holds true, there are now many factors that we know that have to be taken into consideration before this “simple” process can take place. I also did not know that equations and graphs are actually constructed just to study the rain and its effects. Also, it did not occur to me that so many factors could cause a change in the storm hydrograph. Factors including: drainage density, shape of basin, steepness of slope, amount of rain, presence of vegetation and rock permeability. The range of these factors is so great that it is hard to imagine that the difference of something as minute as rock permeability as compared to something as large as drainage density can both have an effect on the hydrograph. Moreover, a simple tweak in only one factor such as the presence of vegetation can actually change the hydrograph by quite a lot. I cannot imagine how much thought has to be put in just to construct a graph that has majority of its factors different from the original graph. Through the learning of these factors, I found out that some things could be inferred from as long as you knew the definition of the term and some background knowledge. For example, the steepness of a slope. From basic knowledge we know that the steeper a slope is, the faster things can roll down. Thus, we then infer that the faster the rain droplets flow down the hill, the shorter is the basin lag time as the river would peak faster. There are some things that we can easily infer when we are studying, we just need to dig out the necessary background information and would be able to arrive at the conclusion.

Janell

The water balance~! by zhang binghui

Hi, everyone! This is Binghui. Today it's my turn to write the blog.

Basically, what we learned today is The Water Balance.

Here is a picture of hydrologic cycle for your better understanding:


The water balance is a simple equation which describes how precipitation may be accounted for within a drainage basin.

A general water balance equation is:
P = Q + E + ΔSwhere
P is total precipitation
Q is total streamflow (runoff)
E is evapotranspiration
ΔS is the change in storage (in soil or the bedrock)

Some examples of the factors:
Q can be affected by dams, but the teacher said not very sure about it.
E can be affected by vegetation
ΔS can be affected by amount of soil and also type of soil.
The water balance is used by hydrologists to plan and manage water supply within a drainage basin. It can be used to suggest possible water shortages for which special measures like hosepipe bans can be implemented to preserve stocks. It has implications too for irrigation, pollution control and flooding. The water balance can be illustrated using a water balance graph which plots levels of precipitation and evapotranspiration often on a monthly scale.
There are some additional points:

1. Precipitation in the form of rain, snow, sleet, hail, etc. makes up the primarily supply of water to the surface. In some very dry locations, water can be supplied by dew and fog.

2. Evaporation is the phase change from a liquid to a gas releasing water from a wet surface into the air above. Similarly, transpiration is represents a phase change when water is released into the air by plants. Evapotranspiration is the combined transfer of water into the air by evaporation and transpiration.

3. Soil moisture storage refers to the amount of water held in the soil at any particular time. The amount of water in the soil depend soil properties like soil texture and organic matter content. The maximum amount of water the soil can hold is called the field capacity. Fine grain soils have larger field capacities than coarse grain (sandy) soils. Thus, more water is available for actual evapotranspiration from fine soils than coarse soils. The upper limit of soil moisture storage is the field capacity; the lower limit is 0 when the soil has dried out.

4. The change in soil moisture storage is the amount of water that is being added to or removed from what is stored. The change in soil moisture storage falls between 0 and the field capacity.

Take note of this, ΔS can be zero. There are some reasons we discussed in class:
1. It can be raining all the time caused the soil saturated, thus ΔS become zero.
2. It can also be no rain at all caused ΔS to be zero.

Lastly, I am not very sure about the question the teacher asked us in class:
Can S be reduced? The answer is yes.
But what is the reason? Can someone who understood this tell me the answer?

I think the lesson is too short, only half an hour.
These are all what we learned.
Thank you!

Binghui
31, 01, 2009

geogpost-o-matic by Matthewlimtianwang

Hey All! This is Matthew And I'll be blogging what we learnt last lesson.
First off, we started talking about water from the hand out that we received.
We deduced that water.
-Has a high specific heat capacity.
>Its able to absorb more heat without turning into gas.
>Very big range in between states, solid, and gas.
-Many many things have water in it.
>Us!
>Plants
>Many things need water to manufacture.
-Drinkable
-Hydrogen bonds
>DNA
>Ice floats
-Ice
>Insulator, it protects the water that is not exposed to the air.
-Universal solvent
-The Earth is mostly water, but we cannot use ocean water as.
ITS TOO SALTY BABY!

okay, time to go on to the next part of the lesson.
the...
HYDROLOGICAL CYCLE
and unusually the caption is,
"what goes around comes around"

Made up of many parts,
Infiltration
Overland flows
etc..

I will scan in the entire picture next week when i get my scanner fixed.
Some terms that we've learnt that day was:
Infiltration Capacity - Rate at which water soaks into the soil.
>affected by:
->Saturation of water.
->Compaction, type of soil.
->Surface area exposed to the water.
->Porous, permeability of the soil.
->If the soil is frozen or not
->Vegetation

Water table - Demarcates the saturated and unsaturated zone, its not the same throughout the year.

Methods of input: Precipitation
Methods of output: Evotranspiration, which is a combination of transpiration and evaporation.

Storages - Groundwater, soil moisture.

Flows - Infiltration, overland flow.

Flows can also be in different categorieroots take in water
Inbetween surface and groundwater - Through flows.
Groundwater - Base flow
Vertically in the soil - Percolation

Interception - Anything that hinders movement of water from precipitation
> Vegetation - reduces impact of rain drops, reduces rain splash erosion.
->stuck in leaves
->roots take in water
->stemflow
->Throughfall






THATS ALL FOLKS!
bwahha.
Matt!