Controlling Water Runoff: factors That Influence Agriculture’s Water Runoff Patterns
Runoff is the overflow of water that occurs when the land’s ability to absorb it is surpassed. It can be caused by a mix of natural events and human activities. This extra water moves across the land and finally ends up in the creeks, streams, or ponds that are close by. Essentially, runoff is the amount of precipitation that travels to rivers and streams after the initial losses.
Surface runoff, sub-surface runoff, and base flow are the three main categories of water runoff.
Surface Runoff:
This is the part of the rain that falls and gets into the stream right away. The extra water creates a head over the ground surface (surface detention) and tends to travel from when all losses are met and the rain falls at a rate faster than its filtering rate one place to another; this occurrence is referred to as overland flow.
When overland flow meets streams, channels, or oceans, surface runoff happens.
Sub-surface Runoff:
It is the part of precipitation that doesn’t connect to streams, rivers, or seas, but instead seeps into the soil first. Because subsurface runoff travels faster than groundwater to reach rivers or channels, it is sometimes referred to as service runoff.
The word “interflow” refers to subsurface runoff.
Base flow:
It is described as the portion of precipitation that enters the soil after it has fallen to the ground, meets the water table, and then runs into streams or the ocean. This kind of runoff is also known as delayed runoff because of how slowly the water moves in it. It requiresa considerable amount of time to connect rivers or seas. Groundwater flow is another name for base flow at times.
Factors Influencing Runoff of Water
Climate and physiographic characteristics are the two main factors that have a considerable impact on water runoff. The watershed’s runoff is closely related to precipitation characteristics, which include the types, intensities, forms, duration, and distribution of precipitation, among other climatic elements.
The dynamics of runoff within a specific area are significantly shaped by the direction of the predominant wind and other climatic factors.
i) Water Runoff and Climate Factors
- Kind of precipitation:
The dynamics of runoff are significantly impacted by various forms of precipitation. For example, when it rains, surface flow is immediately triggered, and the amount and intensity of the runoff determine how far it flows.
On the other hand, precipitation that takes the shape of hail or snow does not immediately contribute to runoff.
2. Rainfall intensity:
Rainfall intensity is a crucial factor in determining runoff yield; higher rainfall intensities lead to faster runoff, while lower rainfall intensities show the opposite trend. Hence, higher rainfall intensities yield more runoff, and lower intensities yield less runoff. This process occurs only after the frozen forms gradually melt. During this melting process, the water infiltrates the soil, leading to minimal surface runoff generation.
3. The length of the rainfall:
Rainfall duration and runoff volume are closely related, mainly because as rainfall continues, the rate at which soil penetration decreases steadily until it stabilizes. Therefore, even a prolonged period of moderate-intensity rainfall can result in a significant and long-lasting runoff.
4. Distribution of rainfall:
The distribution pattern of rainfall has a major impact on runoff in a watershed. The “distribution coefficient,” which is the ratio of the highest rainfall at a particular location to the mean rainfall for the entire watershed, can be used to quantify this distribution.
A greater distribution coefficient results in increased runoff, while a lower value results in decreased runoff, provided that all other variables stay constant and the total rainfall is constant.
It’s crucial to remember that the location of the storm’s center inside the basin—especially at the outflow or in the lower portion of the watershed—can affect the quantity of runoff even with the same distribution coefficient.
5. The predominant wind’s direction:
The predominant wind’s direction greatly influences the dynamics of runoff and has a significant impact on drainage systems.
When the direction of the predominant wind coincides with the natural flow patterns, the drainage system has a greater impact on the peak flow amount and the amount of time it takes surface runoff to reach the outlet.
As a result, storms that follow the natural course of the stream produce a peak flow that is faster and more intense than storms.
6. Other climatic factors:
A number of meteorological variables, such as temperature, wind speed, relative humidity, and yearly precipitation, have an impact on the total amount of water lost in a watershed, which in turn affects the amount of runoff. In other words, runoff decreases when these losses are more noticeable, and runoff rises in reaction when these losses are lessened.
ii) Physiographic Factors Influencing Runoff of Water
A watershed’s physiographic aspects include both the watershed’s features and its channel. The combination of these characteristics is crucial in determining runoff.
The watershed’s dimensions and form, as well as its slope and orientation, land use, soil moisture content and type, topography, and drainage density, are some of the factors that affect runoff.
These variables show how interrelated they are in regulating patterns of water flow and runoff, as they jointly determine the hydrological behavior of a watershed and its associated channels.
a) The watershed’s size
Regardless of the size of the watershed, two watersheds will generate the same amount of water if all other parameters, such as the depth and intensity of rainfall, are equal.
roughly the same quantity of runoff. However, the peak flow and depth are smaller in a broad watershed because it takes longer for the runoff to drain to the outflow, and vice versa.
c). The watershed’s shape:
The way a watershed is shaped greatly affects drainage. The shape of a watershed is frequently described by the phrases “form factor, compactness, and coefficient”.
c). The watershed’s slope:
Although the impact of the watershed’s slope on runoff is complex, it is nonetheless significant. It regulates when rainfall concentrates in the drainage channel and when overland flow occurs, which adds up to the effect on the peak runoff that results.
For instance, in a steep watershed, peak runoff forms quickly because of the faster runoff velocity, which also reduces the time it takes to reach the flow at the outflow.
d). The watershed’s orientation:
This component influences the amount of heat received from the sun, which in turn affects transpiration and evaporation losses in the area. The watershed’s orientation—north or south—affects how quickly accumulated snow melts. In a mountainous watershed, the leeward side of the watershed has a lesser intensity of rainfall, while the windward side of the mountain receives a higher intensity of rainfall, leading to a greater runoff yield.
e). Use of land:
The pattern of land usage and land management. The methods used have a big influence on runoff yield. For instance, there is less surface runoff in a forested area where a thick layer of leaves and grasses has developed because the earth has absorbed more rainwater. In a desolate field with no suitable cover, a reverse tendency is seen.
f). Moisture content of soil:
The quantity of moisture in the soil at the time of rainfall determines the size of the runoff output. Rain significantly reduces the penetration rate of moist soil, increasing the runoff output. In a similar vein, the earth absorbs a significant amount of precipitation when it rains after a protracted dry spell. However, when it rains, runoff yield has the reverse impact.
g). Type of soil:
The kind of soil in the watershed has a big impact on surface runoff because the infiltration rate, which changes depending on the type of soil, determines how much water is lost from the soil.
h). Topographical features:
These include additional watershed topographical elements that affect runoff. Because of the surface’s slope and the length of time it takes for the water to seep into the soil, the runoff water’s undulating form is essentially what permits more electricity to flow.
Conclusion:
Efficient management of our environment and water resources depends on our ability to comprehend the complexity of water runoff. It involves a nuanced interaction between human and natural elements, ranging from the size and form of watersheds to the kind and intensity of precipitation. The hydrological behavior of a specific area is shaped by physiographic parameters including watershed size, slope, and land use, in addition to climatic elements like rainfall patterns and wind direction.
It is impossible to overestimate the influence of human activity on runoff because of urbanization, deforestation, and land
Management techniques have the potential to change runoff patterns, which could result in problems like more flooding or less water availability. Therefore, a comprehensive strategy that considers both natural and anthropogenic elements is needed to manage and mitigate the effects of water runoff.
We can better manage and conserve our limited water resources, lower the chance of floods, and make more informed decisions on land use and environmental preservation by developing a greater understanding of the variables influencing water flow. In a world that is changing, this information is crucial for sustainable water management.
