6th April

Hi class(:
Don't forget:
TERM FOUR, WEEK TWO
We've got our 2nd MCQ Geog test!

Anyway, our last lesson, we learnt about water balance and how to calculate it.

The basic equation would be

P = E + Q ± ∆S

This equation basically accounts for the Inputs, Outputs and Storage changes within a watershed.

A majority of the input is due to precipitation, more commonly known as rain.

A majority of the output is due to evapotranspiration, and storage is the water that is held in the soil.

From this, we can read the equation more easily, if we take P to stand for total precipitation, E for Evapotranspiration, Q for total runoff and S for soil water storage.

Soil water is constantly changing, therefore the triangle stands for the change in S.

Then we moved on to the worksheet, about how human activities affect the hydrological cycle.

Damming, which is usually done to harness hydroelectric power, to prevent flooding, for irrigation purposes or as a tourist attraction, increases surface storage, and thus evaporation as well as reduces runoff.

Cloud seeding causes an increase in impurities in the water vapour in the air, which results in an increase in condensation and therefore an increase in precipitation. This increase causes all other flows to directly increase.

Agriculture causes a decrease in interception/increased infiltration because the crop rows leave a lot more bare soil than when compared to a forest. Ploughing also helps to increase infiltration because the soil gets loosened and thus more water can seep into the earth.

Grazing by animals reduces infiltration beause animals stand and pound and compact the soil, causing the top layer to have fewer air spaces which can be filled by water. So the top soil layer quickly reaches field capacity.

Urbanization causes a reduction in infiltration and an increase in surface runoff due to the cement pavements. The concrete also traps more heat, resulting in a slight increase in evaporation. Increased surface storage also causes an increase in evaporation. The lack of vegetation causes a reduction in evapotranspiration.


Okay yeap, that's pretty much it for 6th April!

Happy Studying!(:

-Nisha (11)☺