Runoff or runoff is called the current of water that is discharged when it exceeds its natural or artificial reservoir or channel. In hydrology, runoff refers to the sheet of water that circulates on the surface in a drainage basin, that is, the height in millimeters of the drained and extended rainwater. It is normally considered as precipitation minus actual evapotranspiration and infiltration of the soil system.
According to Horton's theory, it is formed when precipitation exceeds the infiltration capacity of the soil. This is only applicable in soils in arid areas and with torrential rainfall. This deficiency is corrected with the saturation theory, applicable to soils in areas of high and constant rainfall. According to this theory, runoff will form when soil compartments are saturated with water.
Runoff is one of the basic processes of the water cycle. It refers to the flow of water from rain or snow melt that circulates on the surface of the soil once it exceeds its evaporation and infiltration capacity. "Infiltration (hydrology)"), as explained by the United Nations Development Program (UNDP). There are different types ranging from superficial, hypodermic and underground.
Surface runoff is one of the main causes of erosion worldwide. It tends to be particularly harmful in poorly permeable soils, such as clay, and in areas with scarce plant cover.
The proportion of water that follows each of these paths depends on factors such as climate, the type of rock or the slope of the terrain. Similarly, in places where there is an abundance of loose or very porous materials, the percentage of water that stagnates is very high.
Parameters that influence runoff
The main parameters that affect runoff are:[1].
• - The intensity of precipitation;.
• - The infiltration capacity of a particular surface; There has been an extraordinary shift in the water balance in favor of runoff – instead of infiltration – as a consequence of the waterproofing of large surfaces near cities and metropolitan areas.[2].
• - The hydraulic condition of the soil or rock; and,.
• - The hydraulic characteristics of the soil or rock.
The comparison between these variables allows obtaining information about the processes that can occur under different situations. The conditions in which the soil is found at the time precipitation occurs will substantially affect runoff. The following cases can be distinguished:
Runoff control
Introduction
Runoff or runoff is called the current of water that is discharged when it exceeds its natural or artificial reservoir or channel. In hydrology, runoff refers to the sheet of water that circulates on the surface in a drainage basin, that is, the height in millimeters of the drained and extended rainwater. It is normally considered as precipitation minus actual evapotranspiration and infiltration of the soil system.
According to Horton's theory, it is formed when precipitation exceeds the infiltration capacity of the soil. This is only applicable in soils in arid areas and with torrential rainfall. This deficiency is corrected with the saturation theory, applicable to soils in areas of high and constant rainfall. According to this theory, runoff will form when soil compartments are saturated with water.
Runoff is one of the basic processes of the water cycle. It refers to the flow of water from rain or snow melt that circulates on the surface of the soil once it exceeds its evaporation and infiltration capacity. "Infiltration (hydrology)"), as explained by the United Nations Development Program (UNDP). There are different types ranging from superficial, hypodermic and underground.
Surface runoff is one of the main causes of erosion worldwide. It tends to be particularly harmful in poorly permeable soils, such as clay, and in areas with scarce plant cover.
The proportion of water that follows each of these paths depends on factors such as climate, the type of rock or the slope of the terrain. Similarly, in places where there is an abundance of loose or very porous materials, the percentage of water that stagnates is very high.
Parameters that influence runoff
The main parameters that affect runoff are:[1].
• - The intensity of precipitation;.
• - The infiltration capacity of a particular surface; There has been an extraordinary shift in the water balance in favor of runoff – instead of infiltration – as a consequence of the waterproofing of large surfaces near cities and metropolitan areas.[2].
• - If the intensity of precipitation is less than the infiltration capacity and the moisture content of the soil is less than its field capacity, the runoff on the surface of the land will be reduced, since the soil will be able to capture an important part of the volume of water that precipitates on it. The subsurface flow will be very reduced, since the water captured is retained by capillarity and will increase the initial moisture content in the soil.
• - When precipitation intensity is less than infiltration capacity and soil moisture content is close to or equal to field capacity, part of the precipitation will eventually become runoff on the ground; However, the volumes will continue to be small. Subsurface flow will be important. It can be noted that this second situation frequently follows from the first, when the precipitation lasts uninterruptedly for a certain period of time.
• - If the precipitation intensity is greater than the infiltration capacity and the moisture content of the soil or rock is less than its field capacity. The soil, presenting a significant moisture deficiency, will allow the water that precipitates, despite the fact that the infiltration capacity is reduced, to be partially used to supply moisture to the soil, with only a relatively small portion draining off.
• - Finally, when the precipitation intensity is greater than the infiltration capacity and the moisture content of the soil or rock is greater than or equal to its field capacity. In this case, since the soil is in a condition close to saturation, it will not allow significant infiltration, so that most of the precipitated water will become runoff on the ground. Subsurface flow will also be important. When the shallow part of a soil does not allow significant infiltration, saturation in a soil will take place only in a portion close to the surface, with the moisture front being unable to advance deeper, thus favoring runoff on the ground.
• - The hydraulic condition of the soil or rock; and,.
• - The hydraulic characteristics of the soil or rock.
The comparison between these variables allows obtaining information about the processes that can occur under different situations. The conditions in which the soil is found at the time precipitation occurs will substantially affect runoff. The following cases can be distinguished:
• - If the intensity of precipitation is less than the infiltration capacity and the moisture content of the soil is less than its field capacity, the runoff on the surface of the land will be reduced, since the soil will be able to capture an important part of the volume of water that precipitates on it. The subsurface flow will be very reduced, since the water captured is retained by capillarity and will increase the initial moisture content in the soil.
• - When precipitation intensity is less than infiltration capacity and soil moisture content is close to or equal to field capacity, part of the precipitation will eventually become runoff on the ground; However, the volumes will continue to be small. Subsurface flow will be important. It can be noted that this second situation frequently follows from the first, when the precipitation lasts uninterruptedly for a certain period of time.
• - If the precipitation intensity is greater than the infiltration capacity and the moisture content of the soil or rock is less than its field capacity. The soil, presenting a significant moisture deficiency, will allow the water that precipitates, despite the fact that the infiltration capacity is reduced, to be partially used to supply moisture to the soil, with only a relatively small portion draining off.
• - Finally, when the precipitation intensity is greater than the infiltration capacity and the moisture content of the soil or rock is greater than or equal to its field capacity. In this case, since the soil is in a condition close to saturation, it will not allow significant infiltration, so that most of the precipitated water will become runoff on the ground. Subsurface flow will also be important. When the shallow part of a soil does not allow significant infiltration, saturation in a soil will take place only in a portion close to the surface, with the moisture front being unable to advance deeper, thus favoring runoff on the ground.