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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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In which of the following season is evaporation loss from free water is large?
winter
spring
Autumn
summer
summer
Evaporation from a free water surface is directly proportional to the vapor pressure deficit and wind speed, both of which reach their annual maximums during the summer season in most parts of India. Higher temperatures increase the kinetic energy of water molecules, facilitating the transition from liquid to vapor phase more readily.
Evaporation from a free water surface is directly proportional to the vapor pressure deficit and wind speed, both of which reach their annual maximums during the summer season in most parts of India. Higher temperatures increase the kinetic energy of water molecules, facilitating the transition from liquid to vapor phase more readily.
E=Kf(u)(es−ea) — Dalton's empirical formula for evaporation
es=6.11×10°237.3+T7.5T — Magnus formula for saturation vapor pressure at temperature T
According to Dalton's Law of Evaporation (E=Kf(u)(es−ea)), evaporation E is a function of the difference between saturated vapor pressure at the water temperature (es) and actual vapor pressure of the air (ea). During summer, intense solar radiation leads to significantly higher es values compared to ea, and high ambient temperatures increase the evaporative demand of the atmosphere.
Evaporation increases with air temperature, solar radiation, and wind velocity.
The vapor pressure deficit (es−ea) is the primary driving force for evaporation.
Summer months experience the lowest relative humidity and highest solar exposure, maximizing potential evaporation.
Pan evaporation measurements are often used as a proxy for lake evaporation using a pan coefficient.
High solar energy availability
Maximized potential evapotranspiration (PET)
Significant loss of stored reservoir water
Reduced hydroelectric power generation potential due to volume loss
Reservoir operation planning
Irrigation water requirement scheduling
Hydrological water balance modeling
The pan coefficient (Cp) is typically around 0.7 for Class A pans in Indian conditions.
Winter, Autumn, and Spring have lower ambient temperatures and solar intensity, resulting in significantly lower evaporation rates compared to the peak of Summer.
D is correct — Summer provides the highest ambient temperature and vapor pressure deficit, which are the primary drivers for evaporation from free water surfaces.
Always remember that in hydrology, evaporation loss is maximized when the air is dry (low humidity) and hot, conditions characteristic of summer afternoons.