Hydrological Cycle Online Test 8th Social Science Lesson 7 Questions in English

Water is one of the most important elements on earth. About 71% of the earth’s surface is covered by water.

Most of the water on earth is saline and it is found in seas and oceans. Salt water contributes 97.2% of available earth water.

Fresh water is available only about 2.8% of the available water. From this about 2.15% of fresh water is available in the form of glaciers and ice caps.

The Fresh water is also available in the form of ground water. This can be extracted economically with the present drilling technologies.

On the total available water in the earth 97.2% of the water is saline water which is not meant for human consumption. The fresh water availability is 2.8% of the total water content.

Out of the 2.8% fresh water about 2.15% is available in the form of glaciers and icecaps. 0.01% is available in lakes and streams.0.25% is available as ground water.

Water resources are useful or potentially useful to humans. Water in India is available in three sources. They are precipitation, surface water and ground water.

Hydrology is the science deals with various aspects of water such as its occurrence, distribution, movement and properties on the planet earth.

The Hydrological cycle can be considered as a closed system for the earth, as the quantity of water involved in the cycle is invariable. Hydrological cycle is a global sun-driven process where water is transported from ocean to atmosphere and to land and back from land to oceans.

Evaporation takes place from the surface water and the transpiration from the plants.

Hydrological cycle is a continuous process of water. The three important phases are Evapotranspiration, precipitation, runoff.

Hydrological cycle is a circulation of water.it is a continuous process which involves three important phases.

There are six main components in hydrological cycle are Evapotranspiration, condensation, Precipitation, Infiltration, percolation, runoff.

Evaporation refers to process in which liquid form of water is changes into gaseous form. Temperature is the prime element which affects the rate of evaporation.

Many of the studies reveal that the oceans , seas and lakes provide nearly 90% of the moisture in the atmosphere through evaporation and the remaining 10% is contributed by plants through transpiration.

The rate of evaporation increases with increase in wind speed and temperature. Decrease in humidity and increase in areal extent of surface water bodies.

Water boils at 100deg Celsius but it actually begins to evaporate at 0deg Celsius or 32deg F.

The rate of transpiration is affected by the temperature, wind, and humidity. The agriculture crop characteristics and the cultivation process also involved in this process.

Condensation refers to the process in which the gaseous form of water changes into liquid form.

Condensation is responsible for the formation of clouds. These clouds produce precipitation which is primary for earth’s water cycle.

Dew, fog and clouds are the three major forms of condensation. Condensation is the opposite of evaporation.

A cloud consists of tiny water droplets or ice particles. The size of droplets range from a couple of microns to 100 microns. Mist is the tiny droplets of water hanging in the air. These droplets from the air are rapidly cooled causing it to change from invisible gas to visible water droplets.

Precipitation refers to all forms of water fall from clouds and reaches the earth. For the occurrence of this precipitation cloud droplets or ice crystals and small droplets are needed.

Fog is suspended tiny water droplets or ice crystals in an air layer next to earth’s surface that reduce the visibility. For aviation purposes the criterion for fog is 10km or less.

The ice crystals formed by deposition of water vapors on a cold surface of an object is known as frost. It forms when the temperature of an object drops below the freezing point of temperature.

The most common form of precipitation is rain. The other common types of precipitation include sleet, Freezing rain, hail and snow.

The rain drops with <0.5mm in diameter is known as drizzle and it takes place from stratus clouds.

The most common form of precipitation is rain. Rain drops with >0.5mm in diameter is known as rain.

The precipitation which takes place in the form of mixture of water droplets and tiny particles of ice is known as Sleet.

The precipitation in which the size of rain drops are <0.5mm in diameter is known as drizzle and the rain drops with >0.5mm is known as rain. The sleet consists of mixture of water droplets and ice particles of 5mm in diameter. Ice pellets which are larger than 5mm in diameter is called as hail or hailstones.

Usually rain drops falling through cold air near the ground do not freeze in the air. Instead the raindrops freeze when they touch a cold surface.

The precipitation which consists of round pellets of ice which are larger than 5mm in diameter is called Hail or Hailstones.

Hail forms only in cumulonimbus clouds during thunderstorms. Hailstones start as an ice pellet inside a cold region of a cloud.

Water vapors in a cloud are converted directly into snow pieces due to lowering of temperature. It is common in polar and mountainous region.

The precipitation in the form of powdery mass of ice is known as Snowfall or snow.

Water vapors in a cloud are converted directly into snow pieces due to lowering of temperature. It appears like a powdery mass of ice.

Infiltration allows the soil temporarily to store water. This is available for plants and organisms in the soil.

The rate of infiltration is influenced by the physical characteristics of the soil, vegetative cover, moisture of the soil and temperature and also the rainfall intensity.

Cloud droplets or ice crystals grow large in size so as to fall through the air. While moving down by collecting some small droplets they become heavy enough to fall out as raindrops.

Water entering the soil at surface of the ground is infiltration .This process is important where rain water soaks into the ground. Some of the water ultimately returns to the surface through springs or low spot down hills.

Percolation is the downward movement of infiltrated water through soil and rock layers. This moves the water through the soil profile and rock layers which leads to the formation of ground water.

The percolation process represents the flow of water from unsaturated zone to the saturated zone.

Runoff is the water that is pulled by gravity across lands surface. It comes from unabsorbed water from rain, snowmelt and other sources.

Percolation process moves the infiltrated water through the soil profile and rock layers to form ground water or become a part of sub-surface runoff process.

Runoff is also a major contributor to the erosion which carves out canyons, gorges and related landforms.

The amount of runoff that can happen depends on the amount of rainfall, porosity of soil, vegetation and slope.

Only 35% of precipitation ends up in the sea or ocean and the remaining 65% is absorbed into the soil.

Base on the time interval between the instance of rainfall and generation of runoff it may be classified into 3types.

Surface runoff is the portion of rainfall enters the stream after immediately after the rainfall. It occurs when the rainfall is longer, heavier and exceeds the rate of infiltration.

The sub-surface runoff is usually referred as interflow.

Base flow is a flow of underground water from a saturated ground water zone to a water channel.

The units of the measurement in hydrology cycle. Evaporation/interception- inches (or) cm Infiltration- inches (or) cm/hour Runoff rate-Cubic feet per second Storage- cubic feet (or) acre feet Warm air can hold more water vapor than the cool air.