Lecture Contents:

Annual world water budgetHydrologic cycleDefinition of precipitationForms of precipitationTypes of precipitationRainfall characteristics

Annual World Water Budget

Hydrological Cycle

Hydrological Cycle

Understanding the hydrologic cycle is essential for:- sustainable agriculture (foods for the growing population)- environmental protection and management- water resources development and management- prevention and control of natural disasters- mitigation of the negative impacts of climatic change

The hydrologic cycle appears to be controlled by climaticconditions (rain, snow, wind, etc.), but there are strong feedback mechanisms between hydrological and meteorological processes.

Ten processes of hydrologic cycle1.Evaporation: Water evaporates from oceans and land surface to become part of atmosphere (water vapor).2. Precipitation: Water vapor is lifted and transported in the atmosphere until it condenses and precipitates on the land or oceans.

3. Interception: Precipitated water intercepted by vegetation

4. Overland flow: Precipitated water overflowing on ground surface

5. Infiltration: Precipitated water infiltrated into ground

6. Subsurface flow: Precipitated water flowing through the soil near land

surface

7. Surface runoff (stream flow): Precipitated water discharged to streams

8. Recharge: Deep percolation to water table

9. Groundwater flow: Movement of water table deeper in soil or rock strata

10. Overflow to oceans: Surface and groundwater returning to oceans

PrecipitationPrecipitationWater reaches to Earth Water reaches to Earth

surface from the surface from the atmosphere in any form.atmosphere in any form.

PrecipitationPrecipitationWater reaches to Earth Water reaches to Earth

surface from the surface from the atmosphere in any form.atmosphere in any form.

PrecipitationForms of Precipitation

Liquid Precipitation1. Rain Fall2. Drizzle

Frozen Precipitation1. Snow2. Hail3. Glaze4. Snow flakes5. Sleet

Rainfall is common form of precipitation..

Forms of Precipitation

snow

rain

Snow Flakessleet

freezing rainhail

Types of Precipitation

1. Cyclonic Precipitation:When air masses rise up with vapors and travel towards low pressure areas resulting into Cyclonic precipitation.i. Frontal precipitationIt is due to flow of warm air mass into a cold region.ii. Non-Frontal precipitationWhen cold air meets with stationary warm air then Non-Frontal Precipitation occurs.

2. Convective Precipitation:It occurs due to natural rising of warm lighter air with vapors into the colder and denser region.

3. Orthographic PrecipitationWhen heavily moisture-laden air stops due to topographic conditions (mountains) and precipitation occurs then it is called orthographic precipitation. Just like in Himalayan regions.

4. Precipitation due to Turbulent Ascent.When turbulence in the velocity of clouds occur due to land surface after long travel on the ocean surface then there will be risen up of clouds into colder regions and precipitation occurs.

Rainfall Characteristics1. Size and Shape Rainfall occurs when

moisture in the atmosphere condenses into drops.

Raindrops occur in any shape up to approximately 9 mm mean diameter after which they tend to break up.

2. Intensity and Duration Amount of water that reaches to

ground surface per unit area is called intensity.

Intensity and duration are usually inversely related, i.e., high

intensity storms are likely to be of short duration and low intensity storms can have a long duration.

Any questions?Any questions?Any questions?Any questions?