Introduction to Environment and Environmental Studies


"Environ" means "surrounding" and "ment" means "action". The meaning of the word "Environment" is the surrounding of an organism.

It denotes the total sum of physical, chemical and biological factors that directly influence the survival, growth, development and reproduction of living organism.

Environment has two parts;
  1. Biotic Part:
            It is made of all living organisms which includes, plant, animals, birds, micro- organisms etc.
  1. Abiotic Part:
            Also Called physical environment. It is the non-living components of environment which includes, light, water, temperature, humanity, soil, air etc.

Types Of Environments:

Environmental Science:

It can be defined as the scientific study of the earth, air, water, living organisms and the man with his impact on environment.

Environmental Engineering:

It can be defined as the application of engineering principles, to the protection and enhancement of quality of environment, public health and public welfare.

For Example, the environmental engineer plans, designs, constructs and operate sewage treatment plant, water treatment plant, air pollution control equipments etc.

Environmental Studies:

It can be defined as branch of study concerned with the environmental disturbances and the minimisation of their impacts through changes in the society (social sciences).

Importance of Environmental Studies:

(Environmental protection starts by creating awareness)

  • It is very important for every person for self-fulfilment and social development.
  • It helps to understand different food chains and ecological balance in nature.
  • It helps to understand and appreciate how the environment is used for making a living and for promoting a material culture.
  • It helps in appreciating and enjoying nature and society.
  • It generates concern for the changing environment in a systematic manner for the future as well as immediate welfare of mankind.
  • It directs attention towards population explosion, exhaustion of natural resources and pollution of environment and throws light on solutions.

Goals of Environmental education:

“To develop a world population that is aware of and concerned about environment as a whole and the problems associated with it, and committed to work individually as well as collectively towards solutions of current problems and prevention of future problems”

Primary objectives: (SPEAK Awareness)
  • Skill: Acquire skills for identifying and solving environmental problems.
  • Participation: To provide an opportunity to be actively involved at all levels in working towards the solution of environmental problems.
  • Evaluation ability: Develop the ability to evaluate environmental measures and education programmes in terms of ecological, economic, social and aesthetic factors.
  • Attitude: Acquire a set of values and feelings of concern; motivation for active participation to improve and protect environment.
  • Knowledge: Gain a variety of experiences and acquire a basic understanding of the environment and its associated problems.
  • Awareness: Acquire an awareness of the environment as a whole and its allied problems and sensitivity.

Components of Environment:

Atmosphere :

The thick, gaseous cover of air surrounding the earth is called atmosphere. It sustains life on earth by removing harmful cosmic and ultraviolet rays through absorption, maintaining heat balance, providing oxygen for respiration and carbon dioxide for photosynthesis.

It is the gaseous envelope surrounding the earth and extends upto 500 kms above the earth’s surface. The composition of the atmosphere is given in Table.

The Structure of the Atmosphere:

The atmosphere is broadly divided into four major zones viz. Troposphere, Stratosphere, Mesosphere and Thermosphere. Characteristics of these zones are pictorially represented below in Fig.

Troposphere is the layer of air nearest to the ground. Temperature decreases with height. The average temperature drops from 15ºC at sea level to –56.5ºC at 11 km above sea level.

It contains 70% of the atmospere's mass. The density of the troposhers decreases with altitude. The air near the ground level is heated by the radiation from earth, but the temperature decreases uniformily with atlitude. this decrease of temperature with altitude is known as lapse rate.

Tropopause is the top of the troposphere, which is a transition layer between Troposphere and Stratosphere.

Stratosphere is the layer of air above the troposphere where temperature increases with height. The average temperature rises to –2.5ºC at 50 km above sea level. Ozone is found in higher concentrations between 20 and 30 km above the surface. Hence sometimes this layer is referred to as the “ozone layer”. Ozone absorbs radiant energy from the sun and hence warmer temperatures are encountered in the stratosphere.
Stratopause is the top of the stratosphere, which is a transition layer between Stratosphere and Mesosphere.

Mesosphere is the layer of air above the stratosphere where temperature decreases with height. The average temperature decreases to –90°C at 90 km. This is the coldest layer of the atmosphere. Mesopause is the top of the mesosphere, which is a transition layer between Mesosphere and Thermosphere.

Thermosphere is the layer of air above the mesosphere. The temperatures in the thermosphere increase with increasing height, but there are not many molecules in this layer. The air becomes less and less dense as we reach space.

This comprises all water resources both surface and ground water. The world’s water is found in oceans and seas, lakes and reservoirs, rivers and streams, glaciers and snowcaps in the Polar Regions in addition to ground water below the land areas. The distribution of water among these resources is as under Table.

The water locked up in the Oceans and Seas are too salty and cannot be used directly for human consumption, domestic, agriculture or Industrial purposes. Only less than 1% of water resources are available for human exploitation.

The upper layer of the earth's crust is called lithospere. It is made up of soil, minarals, rocks and other organic as well as inorganic matter. The lithosphere covers the crust of the earth and is extended up to 100 km. 

It is that portion of the earth's surface, hydrosphere and atmosphere where life exists. Biosphere is a biological environment where living organisms interact with physical environment, e.g. soil, water and air.

Factors affecting Choice & Selection of Irrigation Methods

Following are some reasons and factors which affect the selection of an irrigation system for a specific area:

Compatibility of the irrigation system:

The irrigation system for a field or a farm must be compatible with the other existing farm operations, such as land preparation, cultivation, and harvest.
  • Level of Mechanization
  • Size of Fields
  • Cultivation
  • Pest Control
The use of the large mechanized equipment requires longer and wider fields. The irrigation systems must not interfere with these operations and may need to be portable or function primarily outside the crop boundaries (i.e. surface irrigation systems).
Smaller equipment or animal-powered cultivating equipment is more suitable for small fields and more permanent irrigation facilities.

Topographical characteristics of area:

Topography is a major factor affecting irrigation, particularly surface irrigation. Of general concern are the location and elevation of the water supply relative to the field boundaries, the area and configuration of the fields, and access by roads, utility lines (gas, electricity, water, etc.), and migrating herds whether wild or domestic.

.Terraced Fields IrrigationPlain fields Irrigation

Field slope and its uniformity are two of the most important topographical factors. Surface systems, for instance, require uniform grades in the 0-5 percent range.

Restrictions on irrigation system selection due to topography include:
  • Groundwater levels
  • the location and relative elevation of the water source
  • field boundaries
  • acreage in each field
  • the location of roads
  • power and water lines and other obstructions
  • the shape and slope of the field

Economics and cost of the irrigation method:

The type of irrigation system selected is an important economic decision.
Some types of pressurized systems have high capital and operating costs but may utilize minimal labour and conserve water. Their use tends toward high value cropping patterns.
Other systems are relatively less expensive to construct and operate but have high labour requirements.
Some systems are limited by the type of soil or the topography found on a field.
The costs of maintenance and expected life of the rehabilitation along with an array of annual costs like energy, water, depreciation, land preparation, maintenance, labour and taxes should be included in the selection of an irrigation system.

Main costs include:
  • Energy
  • Water
  • Land Preparation
  • Maintenance
  • Labor
  • taxes


The soil's moisture-holding capacity, intake rate and depth are the principal criteria affecting the type of system selected.
Sandy soils typically have high intake rates and low soil moisture storage capacities and may require an entirely different irrigation strategy than the deep clay soil with low infiltration rates but high moisture-storage capacities.
Sandy soil requires more frequent, smaller applications of water whereas clay soils can be irrigated less frequently and to a larger depth. Other important soil properties influence the type of irrigation system to use.

Soil Moisture CapacitySoil Depth Factor in Irrigation Method Selection

The physical, biological and chemical interactions of soil and water influence the hydraulic characteristics and filth. The mix of silt in a soil influences crusting and erodibility and should be considered in each design. The soil influences crusting and erodibility and should be considered in each design.
The distribution of soils may vary widely over a field and may be an important limitation on some methods of applying irrigation water.

The soil type usually defines:
  • Soil moisture-holding capacity
  • The intake rate
  • Effective soil depth

Water supply:

The quality and quantity of the source of water can have a significant impact on the irrigation practices. Crop water demands are continuous during the growing season. The soil moisture reservoir transforms this continuous demand into a periodic one which the irrigation system can service. A water supply with a relatively small discharge is best utilized in an irrigation system which incorporates frequent applications. The depths applied per irrigation would tend to be smaller under these systems than under systems having a large discharge which is available less frequently. The quality of water affects decisions similarly. Salinity is generally the most significant problem but other elements like boron or selenium can be important. A poor quality water supply must be utilized more frequently and in larger amounts than one of good quality.

Crops to be irrigated:

The yields of many crops may be as much affected by how water is applied as the quantity delivered. Irrigation systems create different environmental conditions such as humidity, temperature, and soil aeration. They affect the plant differently by wetting different parts of the plant thereby introducing various undesirable consequences like leaf burn, fruit spotting and deformation, crown rot, etc. Rice, on the other hand, thrives under ponded conditions.

Definition of Cash Crops:

Some crops have high economic value and allow the application of more capital-intensive practices, these are called "cash crops" or Cash crop farming. Deep-rooted crops are more amenable to low-frequency, high-application rate systems than shallow-rooted crops. Examples of cash crops are Rice, Wheat, Seed Oils, Tobacco, cotton, sugar cane, etc.

Crops Covered Wheat Cash Crop irrigationTea Cash Crop irrigation
Cash Crop Water Requirement

Crop characteristics that influence the choice of irrigation system are:
  • The tolerance of the crop during germination, development and maturation to soil salinity, aeration, and various substances, such as boron
  • The magnitude and temporal distribution of water needs for maximum production
  • The economic value of the crop

Social influences on the selection of irrigation method:

Beyond the confines of the individual field, irrigation is a community enterprise. Individuals, groups of individuals, and often the state must join together to construct, operate and maintain the irrigation system as a whole. Within a typical irrigation system there are three levels of community organization.

There is the individual or small informal group of individuals participating in the system at the field and tertiary level of conveyance and distribution. There are the farmer collectives which form in structures as simple as informal organizations or as complex as irrigation districts. These assume, in addition to operation and maintenance, responsibility for allocation and conflict resolution. And then there is the state organization responsible for the water distribution and use at the project level.

Irrigation system designers should be aware that perhaps the most important goal of the irrigation community at all levels is the assurance of equity among its members. Thus the operation, if not always the structure, of the irrigation system will tend to mirror the community view of sharing and allocation.

Irrigation often means a technological intervention in the agricultural system even if irrigation has been practiced locally for generations. New technologies mean new operation and maintenance practices. If the community is not sufficiently adaptable to change, some irrigation systems will not succeed.

External influences:

Conditions outside the sphere of agriculture affect and even dictate the type of system selected. For example, national policies regarding foreign exchange, strengthening specific sectors of the local economy, or sufficiency in particular industries may lead to specific irrigation systems being utilized. Key components in the manufacture or importation of system elements may not be available or cannot be efficiently serviced. Since many irrigation projects are financed by outside donors and lenders, specific system configurations may be precluded because of international policies and attitudes.


Causes of failure of Weirs & their Remedies

Common causes of failure of weirs include:

  • Excessive and progressive downstream erosion, both from within the stream and through lateral erosion of the banks.
  • Erosion of inadequately protected abutments.
  • Hydraulic removal of fines and other support material from downstream protection (gabions and aprons) resulting in erosion of the apron protection.
  • Deterioration of the cutoff and subsequent loss of containment.
  • Additional aspects specific to concrete, rockfill or steel structures.


  • Piping is caused by groundwater seeping out of the bank face. Grains are detached and entrained by the seepage flow and may be transported away from the bank face by surface runoff generated by the seepage, if there is sufficient volume of flow.
  • The exit gradient of water seeping under the base of the weir at the downstream end may exceed a certain critical value of soil. As a result the surface soil starts boiling and is washed away by percolating water. The progressive erosion backwash at the upstream results in the formation of channel (pipe) underneath the floor of weir.
  • Since there is always a differential head between upstream & downstream, water is constantly moving form upstream to downstream from under the base of weir. However, if the hydraulic gradient becomes big, greater than the critical value, then at the point of existance of water at the downstream end, it begins to dislodge the soil particles and carry them away.
  • In due course, when this erosion continues, a sort of pipe or channel is formed within the floor through which more particles are transported downstream which can bring about failure of weir.
  • Piping is especially likely in high banks backed by the valley side, a terrace, or some other high ground. In these locations the high head of water can cause large seepage pressures to occur. Evidence includes: Pronounced seep lines, especially along sand layers or lenses in the bank; pipe shaped cavities in the bank; notches in the bank associated with seepage zones and layers; run-out deposits of eroded material on the lower bank.


  • Decrease Hydraulic gradient i.e. increase path of percolation by providing sufficient length of impervious floor.
  • Providing curtains or piles at both upstream and downstream.


If the weight of the floor is insufficient to resist the uplift pressure, the floor may burst. This bursting of the floor reduces the effective length of the impervious floor, which will resulting increasing exit gradient, and can cause failure of the weir.


  • Providing impervious floor of sufficient length of appropriate thickness.
  • Pile at upstream to reduce uplift pressure downstream.


Hydraulic jump formed at the downstream of water.


  • Additional thickness
  • Floor thickness in one concrete mass


Scouring in Weirs Occurs due to contraction of natural water way.

  • Piles at greater depth than scour level

(Courtesy :