Water resources: Environmental sciences, Notes, MCQ, Books, PDF
EVS Notes Unit I Multidisciplinary nature, Natural Resources, Forest resources, Water resources, Mineral resources, Food resources, Energy resources, Land resources, Role of an individual Unit II Introduction structure-function, Forest eco-system; Grassland ecosystem; Desert ecosystem; Aquatic ecosystems Unit III Air pollution, Water pollution, Soil pollution
Water is an indispensable resource for life on earth. Approximately 70.8 % surface of the earth is covered with water in the form of oceans. Out of this, about 97% is not fit for human consumption, about 2% is locked as a glacier and only less than 1% is available as fresh water that can be used for human consumption and other uses.
Water is a very important source and essential for life because it has very unique characteristics such as
- Water exists as a liquid over a wide range of temperatures 0-1000C with the highest specific heat and latent heat of vaporization.
- Water is an excellent solvent and act as a carrier of nutrient and helps to distribute them to the cells in the body, regulates the body temperature and support structure and can dissolve various pollutant and can act as a carrier of a large number of microorganisms
- It is responsible for the hydrological cycle which acts as a resource of water to the earth. It is estimated that about a 1.4-inch thick layer of water evaporates and the majority returns to the earth through the hydrological cycle.
More than 99% of the earth’s water is unavailable for use; only 1% of water is available for people, animals, plants and the earth. There is an uneven distribution of water resources, tropical rain forests receive maximum rainfall whereas deserts receive only a little rainfall.
Due to its unique properties water is of multiple uses for all living organisms.
Water is absolutely essential for all living organisms. One can survive for weeks without food but cannot survive more than a few days without water. Since the earliest days of mankind, water availability was the major factor to decide the place of human settlements. Water dissolves nutrients and distributes them in different parts of plants and regulates the temperature and removes the waste.
Fresh water crisis
- On a global scale, water availability is not a problem itself, but its availability in the right form, right time and right place is a problem. Irregularities in duration and intensity of rainfall cause floods and droughts. Out of the total water reserves of the world, about 97% is salty water (marine) and only 3% is fresh water.
- Due to increased demands overuse of groundwater for drinking, irrigation and domestic purposes has led to rapid depletion of groundwater in various regions leading to the lowering of the water table.
- Pollution of many of the groundwater aquifers has made them unfit for consumption.
- Rivers and streams have long been used for discharging wastes.
- Due to industrialization river water is being polluted because industrial residues are pushed into the river.
- Civilizations have grown and flourished on the banks of rivers, but being overpopulated due to fast growth is polluting the natural resources of water.
Problems associated with water resources
These are some problems associated with the use of water
• Water Scarcity (precipitation/evapotranspiration balance, temporal availability, per capita availability)
• Floods and droughts (Spatio-temporal distribution; regular floods related to heavy winter or spring rains, increasing damage level due to shifting land use (settlements in flood zones) recurrent summer droughts coinciding with peak demand periods for agriculture and tourism)
• Groundwater availability and quality (aquifer size and access, yield, saltwater intrusion, pollution of shallow aquifers)
• Watershed degradation (deforestation, land use, increasing impervious (sealed) areas due to urbanization the main concern here is land-use change (primarily deforestation and urbanization) and its effects on runoff patterns (flooding) and water quality including erosion/sediments with subsequent problems such as reservoir siltation/capacity loss)
• Coastal interaction (salinity intrusion in groundwater and estuaries, coastal pollution due to pollution runoff)
Over-Exploitation of Water
About 9.86% of the total freshwater resources are in the form of groundwater and it is about 35-50 times that of surface water supplies.
Effects of extensive and reckless groundwater usage:
- Lowering of the water table
- Water logging
ii) Surface water
Surface water mainly comes directly from rain or snow covers. The various surface sources are natural lakes and ponds, rivers and streams, and artificial reservoirs. The availability of surface water decides the economy of the country. On one side surface, water availability affects productivity, but on the other side, water sources may cause floods and drought. Due to unequal distribution, water may lead to national (interstate) or international disputes. Sharing of surface water due to these disputes is affecting the productivity of different agro eco-zone and creating problems for the government. Recently many water conflicts at national and international levels relating to sharing of surface water are catching the headlines of newspapers.
Dams – Benefits and Problems
Water is a precious resource and its scarcity is increasing at the global level. There is pressure to utilise surface water resources efficiently for different purposes.
According to World Commission on Dam Report -2001, there are 45000 large dams spread over 140 countries
Major benefits of dams
The major benefits of dams are
- Hydroelectricity generation
- Year-round water supply to ensure higher productivity
- Equal water distribution by transferring water from an area of excess to an area of deficit
- Helps flood control and protects the soil
- Assure irrigation during dry periods
- River valley projects provide inland water navigation, and employment opportunities and can be used to develop fish hatcheries and nurseries
- River valley projects have tremendous potential for economic upliftment and will help to raise the standard of living and can help to improve the quality of life
Although dams have proved very useful over the centuries recent past big dams have created a lot of human as well as environmental issues
- Submergence of large areas may lead to loss of fertile soil and displacement of tribal people
- Salt left behind due to evaporation increase the salinity of river water and makes it unusable when reaches downstream
- Siltation and sedimentation of reservoirs not only make dams use less but also is responsible for the loss of valuable nutrients
- Loss of non-forest land leads to loss of flora and fauna
- Changes in fisheries and the spawning grounds
- Stagnation and water logging near reservoir leads to the breeding of vectors and the spread of vector-borne diseases
- The growth of aquatic weeds may lead to microclimatic changes
First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise
Pharma News Today 08 Nov 2022
Pharma News Today 07 Nov 2022
Pharma News Today 06 Nov 2022