The hydrologic cycle The hydrologic cycle and water resource of and water resource of

worldworld

• BY - KAKALI ROY BY - KAKALI ROY

• Hydrology means the science of the water. It is Hydrology means the science of the water. It is the science that deals with the occurrence , the science that deals with the occurrence , circulation and distribution of water of the earth circulation and distribution of water of the earth and it’s atmosphere.and it’s atmosphere.

• Hydrology is a very broad subject of an inter – Hydrology is a very broad subject of an inter – disciplinary nature drawing support from allied disciplinary nature drawing support from allied sciences such as meteorology, geology , statistics , sciences such as meteorology, geology , statistics , chemistry, physics and fluid mechanics.chemistry, physics and fluid mechanics.

World water balance and water World water balance and water resource of the earth by unesco 1975resource of the earth by unesco 1975

Global Hydrological Global Hydrological CycleCycle

• The various aspects of water related to the earth The various aspects of water related to the earth can be explained in terms of a cycle Known as can be explained in terms of a cycle Known as Hydrological cycle.Hydrological cycle.

• The sun provides the energy for the evaporation The sun provides the energy for the evaporation of the sea water and gravitational field and of the sea water and gravitational field and coriolis force contribution to the circulation of coriolis force contribution to the circulation of water.water.

PrecipitationPrecipitation

• The water vapor that accumulates or The water vapor that accumulates or freezes on condensation nuclei is freezes on condensation nuclei is attracted on by gravity and falls to Earth’s attracted on by gravity and falls to Earth’s surface.surface.rain, dew, sleet, snow, or hail

InterceptionInterception

Interception: when it rains Interception: when it rains over a catchment, not all the over a catchment, not all the precipitation falls directly on precipitation falls directly on to the ground. Before it to the ground. Before it reaches the ground, a part of reaches the ground, a part of it may be caught by the it may be caught by the vegetation and subsequently vegetation and subsequently evaporated. The volume of evaporated. The volume of water so caught is called water so caught is called interceptioninterception..

1.It maybe retained the vegetation as 1.It maybe retained the vegetation as surface storage and returned to the surface storage and returned to the atmosphere by evaporation a process atmosphere by evaporation a process termed interception loss.termed interception loss.

2. It can be drip off the plant leaves to 2. It can be drip off the plant leaves to join the ground surface or the surface join the ground surface or the surface flow , this is known as through fall .flow , this is known as through fall .

3. The rain water may run along the 3. The rain water may run along the leaves and branches and down the stem leaves and branches and down the stem to reach the ground surface .This is to reach the ground surface .This is called stem flowcalled stem flow. .

DepressioDepression storagen storage

• Depression StorageDepression Storage: : when the when the precipitation of a storm precipitation of a storm reaches the ground, it must reaches the ground, it must fill- up all depressions before fill- up all depressions before it can flow over the surface. it can flow over the surface. The volume of water tapped The volume of water tapped in these depression is called in these depression is called depression storage.depression storage.

• Depression storage depends Depression storage depends on these chief factors on these chief factors

• 1.the type of soil, 2. the 1.the type of soil, 2. the condition of the surface condition of the surface reflecting the amount and the reflecting the amount and the nature of depression,3. the nature of depression,3. the slope of the catchment , 4.the slope of the catchment , 4.the antecedent precipitation as a antecedent precipitation as a measure of soil moisture.measure of soil moisture.

InfiltratioInfiltrationsns • Infiltration: is the flow of water Infiltration: is the flow of water

into the ground through the soil into the ground through the soil surfacesurface..

• At the top , a thin layer of At the top , a thin layer of saturated zone is created .saturated zone is created .

• Beneath zone there is a transition Beneath zone there is a transition zone.zone.

• The next zone is transmission The next zone is transmission zone where the downward zone where the downward moisture takes place.moisture takes place.

• The last zone is the wetting The last zone is the wetting zone . The soil moisture zone will zone . The soil moisture zone will be at or near the field capacity be at or near the field capacity and the moisture content and the moisture content decreased with the depthdecreased with the depth..

RunoffRunoff

• Runoff: is draining or flowing of precipitation Runoff: is draining or flowing of precipitation from a catchment area through a surface from a catchment area through a surface channel. It thus represents the output from the channel. It thus represents the output from the catchment in a given unit of time.catchment in a given unit of time.

InterflowInterflow• Interflow: A part of precipitation that infiltrates Interflow: A part of precipitation that infiltrates

moves laterally through upper layer of the soil moves laterally through upper layer of the soil and returns to the surface at some location away and returns to the surface at some location away from the point of entry in to the soil.(through from the point of entry in to the soil.(through flow).flow).

EvaporationEvaporation•The process by which liquid water is transformed into a gaseous state.

•Evaporation into a gas ceases when the gas reaches saturation.

•The molecules that escape the condensed stage have above-average energies.

•Those left behind have below-average energies .

•Manifested by a decrease in the temperature of the condensed phase.

EvaporationEvaporation

TranspirationTranspiration • Transpiration: is the process Transpiration: is the process by which water leaves the by which water leaves the body of a living plant and body of a living plant and reaches the atmosphere as reaches the atmosphere as water vapour.The water is water vapour.The water is taken up by the plant-root taken up by the plant-root system and escapes through system and escapes through the leaves.the leaves.

• The important factors The important factors effecting transpiration are :effecting transpiration are :1.pressure,2. temperature,3. 1.pressure,2. temperature,3. wind,4. light intensity,4. wind,4. light intensity,4. characteristics of the plant characteristics of the plant such as root and leaf system such as root and leaf system of the plant.of the plant.

Process of Process of hydrological cyclehydrological cycle

• Water of the oceans evaporated due to heat energy Water of the oceans evaporated due to heat energy provided by the solar radiation .provided by the solar radiation .

• The water vapors move upwards and forms clouds . The water vapors move upwards and forms clouds . While much of the clouds condense and fall back to While much of the clouds condense and fall back to the oceans and land as precipitation. Some part of it the oceans and land as precipitation. Some part of it may evaporate back to the atmosphere even falling . may evaporate back to the atmosphere even falling .

• Another part may be intercepted by vegetation, Another part may be intercepted by vegetation, structure and other surfaces modification, or some structure and other surfaces modification, or some part move down to the ground surface.part move down to the ground surface.

• A portion of water that reaches the ground enters A portion of water that reaches the ground enters the earth's surface through infiltration enhances the the earth's surface through infiltration enhances the moisture content of the soil and reach the moisture content of the soil and reach the groundwater body.groundwater body.

• Vegetations sends a portion of the water from Vegetations sends a portion of the water from under the ground surface back to the atmosphere under the ground surface back to the atmosphere through the process of transpiration.through the process of transpiration.

• The precipitation reaching the ground surface The precipitation reaching the ground surface after meeting the needs infiltration and after meeting the needs infiltration and evaporation moves downward the natural slope evaporation moves downward the natural slope over the surfaces and trough a network of over the surfaces and trough a network of gullies , streams and rivers to reach the ocean.gullies , streams and rivers to reach the ocean.

• The ground water may come to the surface The ground water may come to the surface through springs and other outlets after spending through springs and other outlets after spending a considerably longer time than he surface flow. a considerably longer time than he surface flow.

• The portion of the precipitation which by a The portion of the precipitation which by a variety of paths above and below the surface of variety of paths above and below the surface of the earth reaches the stream channel is call the earth reaches the stream channel is call runoff. runoff.

• Once it enters a stream channel runoff becomes Once it enters a stream channel runoff becomes stream flow. It is seen that the hydrologic cycle is stream flow. It is seen that the hydrologic cycle is a very vast and complicated cycle.a very vast and complicated cycle.

• Thank youThank you