When we speak of the hydrological cycle we must differentiate several events that are those that are marking the flow of water. One of these events is the runoff. It is known by the name of surface runoff and is the concept that describes the flow of water, rain, snow or other fluids on the ground. This part makes up a key piece in the water cycle.
In this article, we are going to tell you what surface runoff is, its importance and where it is generated from.
What is surface runoff
When we speak of surface runoff we speak of that it occurs on the surface and that it takes place before reaching a channel such as a river or a lake. In this runoff we find as much water from rain as any other fluid from polluting discharges. When it comes to surface runoff, if it takes place before reaching a channel, it is called a non-point source. If this non-point source has artificial pollutants it is known as non-point source pollution.
The entire area that is responsible for producing the drainage of this runoff to become groundwater and the base of a large amount of water resources is known as the watershed. We know that many man-made discharges are produced both from chemical fertilizers and from other industrial discharges to surface waters. For this reason, it is necessary to analyze whether the runoff that flows along the land can collect pollutants found in the soil. These contaminants can be oil, pesticides, herbicides, insecticides and fertilizers, among others. The relevance of these pollutants in surface runoff is crucial to understanding their impact on the environment and health, so it is recommended to read more about floods and its effects.
Origin and generation of runoff
As we have mentioned before, the origin of the runoff can be generated by precipitation or by melting of snow, today ice in the glaciers. When the melting of glacier snow occurs, when the melting season arrives, it usually occurs only in quite cold areas. This snow runoff usually reaches a peak in the spring time when temperatures riseGlaciers melt completely in summer, producing a peak runoff flow, and river flow is affected by them. All this water ultimately increases river flow and soil erosion. The determining factor in the rate of snow or glacier melting is air temperature and the duration of incident solar radiation. To learn more about these processes, it is useful to consult information on hydrogeology.
We speak of valleys in V when they are glacial valleys given that a large amount of flow is collected in the river in a short time. Only during the thaw season did we find a flow in the river strong enough to erode and transform the land. On the other hand, when we talk about a U-shaped valley, we are talking about a conventional valley. This formation is due to the fact that the flow of the river flow is constant throughout the year. In these cases we also have times of less water flow during the summer season.
High mountain regions have streams that rise on sunny days and decrease on cloudy days due to less solar radiation. In areas where there is no snow the runoff comes from precipitation. It should be mentioned that not all rainfall generates runoff. Precipitation runoff is generated when the soil cannot store large amounts of water due to heavy downpours.
For example, there are very old soils in Australia and southern Africa where proteoid roots exist. These roots are so dense and have so many hairs that they are capable of absorbing large amounts of rainwater. Thus, It is difficult for runoff water to exist as they are capable of absorbing substantial amounts of rain. In addition, there must be a low potential for evaporation for surface runoff to last longer.
Overland water flow with excess infiltration
An important aspect to consider in surface runoff is the infiltration process. It is the process in which water infiltrates the underground part of the earth. Here the water is stored in aquifers and serves as a water resource. Almost any basin there are small underground water stores. This infiltration occurs less frequently in arid and semi-arid regions where the intensities of precipitation is higher and infiltration rate lower due to the waterproofing of the surface.
It also occurs in greater amounts of surface runoff and lower infiltration rates on paved soils. Another aspect is oversaturation overland flow. This is a condition that leads to greater surface runoff. In this case, the soil is saturated with water, and the basin has stored as much as possible. In these cases, greater surface runoff will occur due to the large amount of precipitation. The level of soil moisture is also a factor that affects the time it takes for the soil to become saturated. The more moisture the soil has, the faster it will become saturated with water. Therefore, it will be able to store less water and will end up creating greater surface runoff. If you want to delve deeper into how these phenomena occur, it is recommended to read about Aquifers.
Human impact on surface runoff
It should be noted that humans greatly influence the amount of existing runoff. And it is that we are continually creating surfaces that are waterproof such as pavements and buildings. These waterproofings mean that the water cannot infiltrate into the aquifer. Instead of the water seeping into the ground, the water forced directly into the streams or drainage where there is greater erosion and sedimentation. These conditions are what cause flooding in the city.
Increased surface runoff reduces groundwater recharge and lowers the water table. These are conditions that they worsen the drought especially for the field of agriculture and all those people who depend on water wells. In addition, to this situation must be added the presence of anthropogenic pollutants dissolved in surface runoff that affect people's health. This load of pollutants can reach waters in rivers, lakes and oceans and contaminate the waters.
I hope that with this information you can learn more about surface runoff.