Evapotranspiration

This paper published in the journal Current Science presents the findings of a study has been taken up to quantify the possible impacts of the climate change on the water resources of Indian river systems within the constraints of the uncertainty of climate change predictions. The study uses the PRECIS daily weather data to determine the spatio-temporal water availability in the river systems.

A distributed hydrological model, namely SWAT has been used to simulate all the river basins of the country. The analysis has been performed to evaluate the severity of droughts and floods and thus identify the vulnerable hotspots that may require attention in view of the climate change in various parts of the country

Impacts of climate change and climate variability on the water resources are likely to affect irrigated agriculture, installed power capacity, environmental flows in the dry season and higher flows during the wet season, thereby causing severe droughts and floods in urban and rural areas. Climate change impacts on water resources which are addressed and analysed in the present study include impacts on annual and inter-annual water availability as well as extreme events of droughts and floods. Read More

This paper by N Subba Rao in Springer Science deals with the problem of high fluoride groundwater. Fluoride is essential for normal bone growth, but its higher concentration in drinking water poses great health problems and fluorosis is common in many parts of India.

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This book by Earthscan contains the global standard for ‘water footprint assessment’ as developed and maintained by the Water Footprint Network (WFN). It covers a comprehensive set of definitions and methods for water footprint accounting. It shows how water footprints are calculated for individual processes and products, as well as for consumers, nations and businesses. It also includes methods for water footprint sustainability assessment and a library of water footprint response options.

A shared standard on definitions and calculation methods is crucial given the rapidly growing interest in companies and governments to use water footprint accounts as a basis for formulating sustainable water strategies and policies. The current manual is an updated, revised and expanded version of Water Footprint Manual: State of the Art 2009, published by the WFN in November 2009 (Hoekstra et al, 2009a). This new edition has been produced after intensive consultations with partners and researchers worldwide. Directly following the publication of the Water Footprint Manual, all partners of the WFN were invited to provide feedback on the manual.

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This study on “Hydrology in Ancient India” by the National Institute of Hydrology, Roorkee summarizes and analyses the knowledge of various aspects of water resources and hydrology as contained in ancient Indian literature. It attempts at compiling information on various component processes of hydrology and their interaction. The report has been divided into nine chapters dealing with different aspects of hydrology.

Like other sciences, the science of water too was well developed in ancient India. The report regrets that at present sufficient attention is not paid to our ancient Indian sciences. The study of Sanskrit literature indicates valuable references to hydrology and important concepts of modern hydrology are scattered in various verses of Vedas, Puranas, Meghmala, Mayurchitraka, Vrhat Sanhita and various other ancient Indian works. 

Some of the key references are as follows –

• In vedic age, Indians had developed the concept that water gets divided into minute particles due to the effect of sun rays and wind. At various places in the Puranas it is alluded that water cannot be created or destroyed and that only its state is changed through various phases of hydrological cycle.
• Evaporation, condensation, cloud formation, precipitation and its measurement were well understood in India in vedic and puranic times.
• Effect of yajna, forests, reservoirs etc., on the causation of rainfall, classification of clouds, their colour, rainfall capacity etc, forecasting of rainfall on the basis of natural phenomenon like colour of sky, clouds, wind direction, lightning, and the activities of animals was well developed in ancient India well before 10th century BC.
• Contrivances to measure rainfall were developed during the time of Kautilya (4th century BC) which had the same principle as that of modern hydrology except the fact that weight measure (of drone, paia etc.,) were adopted instead of modern linear measurement of rainfall.
• Scientific facts like arid region of Tibetan rain shadow area and no rainfall by polar winds was discussed in the puranas. The knowledge of monsoon winds and height of clouds along with the division of atmosphere was well developed in vedic age.
• The technique of knowing the slope of an area by means of a flowing river and dimensions of meandering rivers along with velocity of flow were developed.
• In ancient times, Indians had well developed concepts of groundwater occurrence, distribution and utilization. Literature also reveals that hydrologic indicators such as physiographic features, termite mounds, soils, flora, fauna, rocks and minerals were used to detect the presence of groundwater.
• Variation in the height of water table with place, hot and cold springs, ground water utilization by means of wells, well construction methods and equipment are fully described in chapter 54 of Vrhat Sanhita (Bruhat Samhita) named as ‘Dakargala’. The fact that sun rays, winds, humidity, vegetation etc are the major causes of evapotranspiration was well realized.
• Varamihira in as early as 550 AD presented a simple method for obtaining potable water from a contaminated source of water. Various plant materials along with the sun heating, aeration, quenching of water with fire heated stones, gold, silver, iron or sand were used. The change in the quality of water with the months of year and suitability of water from different sources for various uses were described.
• Efficient water use, lining of canals, construction of dams, tanks, essential requirements for the construction of good tanks, bank protection methods, spillways and other minor aspects were given due consideration in ancient times in India.
• Well organized water pricing system was prevalent during the times of Kautilya.
• Various references are available in the Vedas alluding the importance of efficient water use so as to reduce the intensity of water scarcity and drought.

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