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Generally drizzle takes place from Stratus clouds.

Percolation moves the infiltrated water through the soil profile and rock layers which leads to the formation of ground water or become a part of sub – surface run – off – process.

The water cycle can be considered as a closed system for the earth, as the quantity of water involved in the cycle is invariable, though its distribution varies over space and time.

Some of the infiltrated water ultimately returns to the surface through springs or low spots down hills. Some of the water remains underground and is called groundwater.

Condensation occurs when the air get saturated.

1. Warm air can hold more water vapour than the cool air.

2. Saturation occurs when the temperature drops down.

Percolation is the downward movement of infiltrated water through soil and rock layers.

Surface Runoff is the portion of rainfall, which enters the stream immediately after the rainfall. It occurs, when the rainfall is longer, heavier and exceeds the rate of infiltration. In this condition the excess water makes a head over the ground surface, which tends to move from one place to another following land gradient and is known as overland flow. When the overland flow joins the streams, channels or oceans, it is termed as surface runoff or surface flow.

1. Water entering the soil at the surface of the ground is termed as infiltration. Infiltration allows the soil temporarily to store water, the rate of infiltration is influenced by the physical characteristics of the soil, vegetative cover, moisture content of the soil, soil temperature and rainfall intensity.

2. Most of the water on the earth is saline and is found in seas and oceans, which constitutes about 97.2%.

3. 1. The precipitation in the form of powdery mass of ice is known as snowfall.

2. Often water vapour in a cloud is converted directly into snow pieces due to lowering of temperature.

3. It is common in the polar and high mountainous regions.

Water that flows in the sub – soil or through the ground into the streams, rivers, lakes and oceans is termed as Runoff

(c) Potable water

The three important phases of the hydrologic cycle are:

• Evapotranspiration,
• Precipitation
• Runoff.

1. Evapotranspiration:

It is defined as the total loss of water from the earth through evaporation from the surface water bodies and the transpiration from vegetation. In cropped area, it is difficult to determine the evaporation and transpiration separately. Therefore it is collectively called as evapotranspiration.

2. Precipitation:

It refers to all forms of water that fall from clouds and reaches the earth’s surface. For the occurrence of precipitation, cloud droplets or ice crystals must grow heavy enough to fall through the air. When the droplets grow large in size, they tend to all. While moving down, by collecting some small droplets, they become heavy enough to fall out of the cloud as raindrops.

3. Runoff:

Runoff is the water that is pulled by gravity across land’s surface. It replenishes groundwater and surface water as it percolates into an aquifer (it is an underground layer of water – bearing rock) or moves into a river, stream or watershed. It comes from unabsorbed water from rain, snowmelt, irrigation or other sources, comprising a significant element in the water cycle as well as the water supply when it drains into a watershed. Runoff is also a major contributor to the erosion which carves out canyons, gorges and related landforms.

Evaporation:

• Process in which the liquid form of water changes into gaseous form.
• Rate of evaporation is affected by temperature, Areal extent of surface water, wind and the atmospheric humidity.
• 90% moisture in the atmosphere is contributed through evaporation. 

Transpiration:

• Process by which the water content in the plant is released into the atmosphere in the form of water vapour.
• Rate of Transpiration is affected temperature, wind and humidity.
• 10% moisture is contributed through Transpiration.

(a) Transpiration

Forms of Precipitation: 

The form of precipitation in a region depends on the kind of weather or the climate of the region. Common types of precipitation include rain, sleet, freezing rain, hail and snow.

Rain:

The precipitation in the form of water droplets is called rain. The precipitation in which the size of rain drops are 0.5 mm in diameter is known as rain. Generally drizzle takes place from stratus clouds. 

Sleet:

The precipitation which takes place in the form of mixture of water droplets and tiny particles of ice(5mm in diameter) is known as sleet. Sometimes raindrops fall through a layer of air below 0°C. As they fall, the raindrops freeze into solid particles of ice. So, the mixture of water droplets and ice particles would fall on the earth surface.

Freezing Rain:

At other times raindrops falling through cold air near the ground do not freeze in the air. Instead, the raindrops freeze when they touch a cold surface. This is called freezing rain.

Hail:

The precipitation which consists of round pellets of ice which are larger than 5 mm in diameter is called hail or hailstones. A hailstone starts as an ice pellet inside a cold region of a cloud.

Snow:

Often water vapour in a cloud is converted directly into snow pieces due to lowering of temperature. The precipitation in the form of powdery mass of ice is known as snowfall. It is common in the polar and high mountainous regions.

The rate of transpiration is also affected by the temperature, wind and humidity. The soil water content and the ability of the soil to conduct water to the roots, the nature of the plant parts including barks and leaves also determine the transpiration rate.

a. ii 

b. iii

c. iv 

d. i

All plants and animals need water for survival. Apart from drinking, water is required for domestic, agriculture, industrial purposes etc. Water is very essential for carrying out almost all economic activities.

(b) 1 and 3 are correct

(b) evaporation

Runoff is the water that is pulled by gravity across land’s surface. It replenishes groundwater and surface water as it percolates into an aquifer (it is an underground layer of water-bearing rock) or moves into a river, stream or watershed.

Types of Runoff:

Based on the time interval between the instance of rainfall and generation of runoff, the runoff may be classified into following three types

1. Surface Runoff:

It is the portion of rainfall, which enters the stream immediately after the rainfall. It occurs, when the rainfall is longer, heavier and exceeds the rate of infiltration. In this condition the excess water makes a head over the ground surface, which tends to move from one place to another following land gradient and is known as overland flow. When the overland flow joins the streams, channels or oceans, it is termed as surface runoff or surface flow.

2. Sub – Surface Runoff:

The water that has entered the subsoil and moves laterally without joining the water-table to the streams, rivers or oceans is known as sub- surface runoff. The sub – surface runoff is usually referred as interflow.

3. Base Flow:

It is a flow of underground water from a saturated ground water zone to a water channel. It usually appears at a downstream location where the channel elevation is lower than the groundwater table. Groundwater provides the stream flow during dry periods of small or no precipitation.

1. Evapotranspiration 

2. Condensation 

3. Precipitation

4. Infiltration 

5. Percolation 

6. Runoff.

1. Drilling 

2. Plants 

3. calm 

4. Mist 

5. 0.5mm 

6. Cumulonimbus 

7. Snow 

8. Unsaturated, saturated 

9. Interflow 

10. Cubic feet per second

Oceans, seas, lakes and rivers provide nearly 90% of the moisture in the atmosphere.

1. Humidity 

2. Three 

3. Precipitation 

4. Drizzle 

5. Fog

(b) Hydrologic Cycle

The percentage of fresh water on the earth is 2.8

About 71 % of the earth’s surface is covered by water.

For aviation purpose, the criterion for fog is 10 km or less.

Transpiration refers to the process by which the water content in the plants are released into the atmosphere in the form of water vapour.

(a) Condensation

1. Evaporation

2. Condensation

3. Precipitation 

4. Transpiration 

5. Runoff

6. Infiltration 

7. Ground water recharge (Percolation)

The rate of evaporation increases with 

1. Increase in wind speed 

2. Increase in temperature 

3. Decrease in humidity and 

4. Increase in areal extent of surface water bodies

The rate of evaporation is low during the periods of calm winds.

Hydrologic cycle is a global sun – driven process where water is transported from oceans to atmosphere, from atmosphere to land and from land back to oceans.

(c) II and III are correct

An aquifer is an underground layer of water – bearing rock.

1. True

2. False

Correct statement: Mist is the tiny droplets of water hanging in the air.

3. True