The environmental effects of irrigation relate to the changes in quantity and quality of soil and water as a result of irrigation and the subsequent effects on natural and social conditions in river basins and downstream of an irrigation scheme. The effects stem from the altered hydrological conditions caused by the installation and operation of the irrigation scheme.
Amongst some of these problems is depletion of underground aquifers through overdrafting. Soil can be over-irrigated due to poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution. Over-irrigation can cause deep drainage from rising water tables that can lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage. However, if the soil is under irrigated, it gives poor soil salinity control which leads to increased soil salinity with the consequent buildup of toxic salts on the soil surface in areas with high evaporation. This requires either leaching to remove these salts and a method of drainage to carry the salts away. Irrigation with saline or high-sodium water may damage soil structure owing to the formation of alkaline soil.
An irrigation scheme draws water from groundwater, rivers, lakes or overland flow, and distributes it over a certain area. Hydrological, or direct, effects of doing this include reduction in downstream river flow, increased evaporation in the irrigated area, increased level in the water table as groundwater recharge in the area is increased and flow increased in the irrigated area. Likewise, irrigation has immediate effects on the provision of moisture to the atmosphere, inducing atmospheric instabilities and increasing downwind rainfall, or in other cases modifies the atmospheric circulation, delivering rain to different downwind areas. Increases or decreases in irrigation are a key area of concern in precipitationshed studies, that examine how significant modifications to the delivery of evaporation to the atmosphere can alter downwind rainfall.
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The course aims at teaching the fundamentals of both irrigation and drainage techniques with particular attention to the soil water balance and related management, the materials, the construction meth
Water resources engineering designs systems to control the quantity, quality, timing, and distribution of water to support human demands and the needs of the environment.
Together, we will continue our exploration of the theme of water by building a set of fountains that we will later attempt to integrate into a domestic project for the port of Basel. The focus will be
Discute de la modélisation des transferts d'eau avec l'équation de Richards, y compris les fonctions hydrauliques du sol, les méthodes numériques, les conditions aux limites et l'impact de l'irrigation.
Alkali, or Alkaline, soils are clay soils with high pH (greater than 8.5), a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity.
The residual sodium carbonate (RSC) index of irrigation water or soil water is used to indicate the alkalinity hazard for soil. The RSC index is used to find the suitability of the water for irrigation in clay soils which have a high cation exchange capacity. When dissolved sodium in comparison with dissolved calcium and magnesium is high in water, clay soil swells or undergoes dispersion which drastically reduces its infiltration capacity. In the dispersed soil structure, the plant roots are unable to spread deeper into the soil due to lack of moisture.
La micro-irrigation est une méthode d'irrigation utilisée en zone aride car elle réduit au maximum l'utilisation de l'eau et de l'engrais. Il existe plusieurs types de micro-irrigation, le plus répandu aujourd'hui étant le « goutte-à-goutte » (souvent raccourci par l'acronyme GAG), où l'eau s'égoutte lentement vers les racines des plantes par un système de tuyaux, soit en coulant à la surface du sol soit en irriguant directement la rhizosphère (on parle alors de goutte à goutte enterré Cette technique israélienne est l'innovation la plus importante dans l'agriculture depuis l'invention des asperseurs dans les , qui avait déjà remplacé à l'époque une irrigation nécessitant trop d'eau.
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