[GATE NOTES] Hydrology – GATE, IES, Govt Exams – Handwritten Notes – Free Download PDF

• PRECIPITATION
• MEAN PRECIPITATION CALCULATION
• FREQUENCY ANALYSIS
• INFILTRATION
• RUNOFF
• HYDROGRAPHS
• MAXIMUM FLOOD ESTIMATION
• FLOOD ROUTING
• WELL HYDRAULICS

Hydrology is a study if science of water.

Hydrology deals with occurrence, movement, distribution and circulation of water above the ground below the ground or even in the atmosphere.

Hydrology deals with depletion and replenishment of water resource of earth.
Objective : To estimate yield water from drainage basin. Drainage basin means watershed or catchment.

Total water available – 1380 million cubic kilometersSaline water – 97.2℅ available waterFresh water – 2.8℅ available waterGlaciers – 2.15℅ available waterDeep below the ground – 0.32℅ available waterTherefore 0.33℅ of total water available for human use and consumption. Average annual precipitation of world = 100 cm

Average annual precipitation = 119.4 cmGeographic area = 3.28 x 10^6 km^2Total volume of water = 3216 cubic kilometers.

Applications :
Design of hydraulic structures
Flood forecasting and management.
Irrigation
Municipal and industrial water supply.
Hydropower generation.
Pollution control.
Navigation
Drought management.
Hydrologic cycle :
Water circulatory cycle which shows how water circulate from one place to other place and from one form to other form with time.

Components of hydrologic cycle :
Precipitation
Evaporation
Transpiration
Evapo-Transpiration
Infiltration
Run off

Precipitation denotes all the forms of moisture that reach ground from atmosphere.

Forms of precipitation :

Rain : Precipitation in the form of water droplets of size greater than 0.5 mm and intensity rate of rain greater than 1mm per hour.
Drizzle : Precipitation in the form of water droplets of size less than 0.5mm and intensity less than 1mm per hour.
Snow : Precipitation in the form of fine ice crystals of size less than 1mm
Sleet : Ice crystals of size 1mm to 5mm is known as sleet.
Hail : Ice Crystals of size greater than 8mm is hail.
Dew : Vapour accumulated during day condenses during night and deposited on the ground as dew.




Types of Precipitation :
Convective Precipitation : This occurs due to hearing of the ground and temperature difference between moist air and it’s surroundings. Ex : Summer rains : high intensity rains occurring for short periods.

Orographic precipitation : It is caused by topographic barriers such as hills and mountains Ex : rains at himalayas and Western ghats moderate intensity rains for longer periods

Frontal Precipitation : Front air : It is an interface between two distinct air masses. Frontal Precipitation are of two types.
i. warm air frontal precipitation
ii. cold air frontal precipitation

Cyclonic precipitation : Precipitation caused by cyclones. Cyclones are large area of low pressure region with circular wind motion. Cyclonic precipitation occurs due to pressure difference between ground and water bodies.
Precipitation due to turbulent ascent : winter rains along with coastal rains.