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Alternate wetting and drying (AWD) is a water management technique, practiced to cultivate irrigated lowland rice with much less water than the usual system of maintaining continuous standing water in the crop field. It is a method of controlled and intermittent irrigation.
The ocean plays a key role in the water cycle as it is the source of 86% of global evaporation. [2] The water cycle involves the exchange of energy, which leads to temperature changes. When water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment.
Surge Irrigation is a variant of furrow irrigation where the water supply is pulsed on and off in planned time periods (e.g. on for 1 hour off for 1½ hour). The wetting and drying cycles reduce infiltration rates resulting in faster advance rates and higher uniformity [4] than continuous flow.
A common method to reduce future swelling in expansive soils is to subject the soil to wetting and drying cycles prior to construction of the lining. [6] Lab testing has shown that subjecting a clayey soil to wetting and drying cycles leads to a hysteresis of shrinkage in the soil, significantly reducing its free swelling potential. [7]
Water cycle. The water cycle (known scientifically as the hydrologic cycle) is the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. Water moves perpetually through each of these regions in the water cycle consisting of the following transfer processes:
Expansive soils are the most problematic in regions with very defined wet and dry periods, as opposed to areas that maintain a certain level of moisture throughout the year, as this annual cycle causes the soils to expand and swell every year. [3] Water can also be introduced into the soil through people, or their infrastructure.
Pluvial lakes represent changes in the hydrological cycle: wet cycles generate large lakes, and dry cycles cause the lakes to recede. Accumulated sediments show the variation in water level. During glacial periods, when the lake level is fairly high, mud sediments will settle out and be deposited.
The surface water visibly seen in wetlands only represents a portion of the overall water cycle, which also includes atmospheric water (precipitation) and groundwater. Many wetlands are directly linked to groundwater and they can be a crucial regulator of both the quantity and quality of water found below the ground.