Introduction hydrology

Presented by:

Muhammad Aleem

It begins with a storm …

They were rolls, waves that finished in a puff: known noises,

village things. Everything that we have here is animated, lively,

maybe because the distances are short and fixed as in a theatre.

The downpours were onto the courtyards here around, the

thunder up here above the roofs; I could recognize by ear, a

little further up, the place of the usual God that made storms

when we were children, He too a village character. Here all is

as if intensified, a matter of scale probably, of inner

relationships. The shape of the noises and of these thoughts

(which were, after all, the same thing) seemed to me for a

moment truer than true, but it cannot be recreated with words

Objectives

“To explain what hydrology is and what it deals with..”

• The elements of the water cycle

• The spatial and temporal scales involved

• The mass and energy balance at a global scale

The Water CycleThe water on Earth flows from the atmosphere to the ground. And then from the rivers to the sea, from where it returns to the atmosphere:

“Hydrology is the science

that studies these flows,

which make up

the water cycle.”

The flows from the atmosphere to the surface of theEarth are called Precipitations. The water thatreaches the ground can infiltrate and flow withinthe soil or it can run off on the surface - these arereferred to as “Horizontal Flows”.

At the same time, there is evaporation from the soil and water surfaces, and transpiration from plants and animals (in a word, evapotranspiration) -Infiltration and evaporation constitute the “Vertical Flows.”

During the first seconds after the Big Bang, Hydrogenand Helium were created. According to the Theories,oxygen was formed a little later. However, it is the thirdelement more diffuse in the

universe.

If you consider that Helium is not very much reactive, it couldn’t be a real surprise that an element built on Hydrogen and Oxygen is abundant on the Earth.

For a given catchment, in an interval of time ∆t, the continuity equation for water in its various phases can be given as:

Mass inflow – Mass outflow = Change In Mass Storage

If the density of the inflow, outflow and storage volumes are the same:

Vi – Vo= ∆S Vi - Inflow volume in to the catchment, Vo - Outflow volume

from the catchment and ∆S - change in the water volume

Therefore, the water budget of a catchment for a time interval ∆t is written as:

P – R – G – E – T = ∆SP = Precipitation

R = Surface runoff

G = net ground water flow out of the catchment,

E = Evaporation

T = Transpiration

∆S = change in storage

The above equation is called the WATER BUDGET EQUATION for a catchment.

Total quantity of water in the world is estimated as 1386 M km3

1337.5 M km3 of water is contained in oceans as saline water

The rest 48.5 M km3 is land water 13.8 M km3 is again saline

34.7 M km3 is fresh water 10.6 M km3 is both liquid and fresh

24.1 M km3 is a frozen ice and glaciers in the polar regions and mountain tops

Estimated World Water Quantitites

96%

1%

1%

2% Ocean-saline

Land - saline

Fresh - Liquid

Fresh - Frozen

• The variation of water production from catchments can be calculated and described by hydrology.

• It is used to find out maximum portable flood at proposed sites. e.g. dam ..

• Used in prediction of flood over a spillway, at highway culvert or in urban storm drainage.

• Used to assess the reservoir capacity required to assure enough water for irrigation or municipal water supply during drought.

• Engineering hydrology enables us to find out the relationship between a catchments' surface water and groundwater resources.

• Used in connection with design and operations of hydraulic structure.

THANK YOU ….

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