Water Management
• Water is the most abundant compound on Earth’s surface, covering 70 per cent of the planet.
• Water present in sea, lakes, rivers, groundwater and stream base flow is called blue water.
• Blue water is extensively used in agriculture.(Water Management)
• Green water denotes soil moisture and water present in plants and used in photosynthesis.
• Grey water is waste water from bathrooms, kitchens and wash basins.
• Grey water is used in crop production, particularly in kitchen gardens and lawns.
• Black water is the water coming out as domestic sewage or industrial waste.
• Black water can be used in crop production after proper treatment.
• The water consumed in the production process of an agricultural or industrial product has been called the ‘virtual water’ contained in the product.
• To produce one kilogram of wheat we need about 1,000 litres of water, i.e. the virtual water of this kilogram of wheat is 1000 litres.
• 400 to 500 litres of water is necessary for the production of a kilo of plant dry matter.(Water Management)
• Water footprint is an indicator of freshwater use that looks at both direct and indirect water use of a consumer or producer.
• Root proliferation is reduced due to high mechanical resistance of dry soil.
• Irrigation is the artificial application of water to soil to supplement rainfall for crop production.
• About 97 % of water is in the oceans and not useful for irrigation.
• Of the total quantity of water, only 2.60 % is fresh water.
• Of the total fresh water, 77.23 % is in polar ice caps, icebergs and glaciers.
• Average rainfall of India is 1194 mm.
• Total quantity of rainfall received on a geographical area of 328 m ha in India is 400 m ha m (including snow fall).
• Out of the 400 m ha m of rainfall, 75 % of it is received during South-west monsoon period (June to September) and the rest in the remaining 8 months.
• 215 m ha m soaks into the soil.(Water Management)
• 70 m ha m is lost as evapotranspiration
• Water moves from higher potential to lower potential.
• Darcy’s law states that the velocity of a fluid in permeable media is directly proportional to the hydraulic gradient.
• In this law, hydraulic conductivity (K) is taken as proportionality constant.
• Darcy stated that the rate of flow increases with an increased depth of water above the bottom of the soil, and decreases with an increased depth of soil, through which water flows.(Water Management)
• Poiseuille’s law expresses the flow of water in a narrow tube. According to it rate of flow of water in sandy soil is more than that of loam and least in the clay. Sandy > loam > clay
• Passive absorption takes place when water is drawn into the roots by negative pressures in the conducting tissue created by transpiration.
• When there is a little transpiration, the roots of many plants absorb water by spending energy which is called active absorption.
• Under normal conditions of transpiration, the contribution of active absorption to the water supply of plants is negligible and it is usually less than 10% of the total absorption.
• Evaporation from the surface of the soil or free water surface or vegetative cover is a diffusive process by which water in the form of vapour is transferred to the atmosphere.
• Transpiration is the process by which water vapour leaves the living plant body and enters the atmosphere.
• Transpiration is basically an evaporative process.
• Amount of water present in the soil does not correctly indicate its availability unless soil type is mentioned.(Water Management)
• At 12 percent soil moisture, crops in alfisols grow normally while those in vertisols show wilting symptoms due to variation in energy status of water in different soils.
• Energy status of water in soil indicates the tenacity with which water is held in the soil and the ease with which it is available.
• Shape of water molecule is a sphere and the position of two hydrogen ions is at the corners of a tetrahedron that exists within a sphere.
• One end of water molecule has positive charge and another end has negative charge making it a dipole.(Water Management)
• Hydrogen in the water serves as a connecting link from one molecule to the other end and it is known as hydrogen bonding.
• Water sticks to itself with great energy and this property is called cohesion.
• Water attaches itself to surfaces of many substances and this property is known as adhesion.
• By adhesion, water is held tightly at the soil-water interface.
• Water contents under certain standard conditions are referred to as soil moisture constants.(Water Management)
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