What is runoff and factors affecting runoff?
What is runoff and factors affecting runoff?
Runoff depends on the intensity of rainfall. More the rainfall, more will be runoff. If the rainfall intensity is very less and it rains as light showers then much of the water will be lost in infiltration & evaporation resulting less runoff. If precipitation is in case of snow then less runoff.
What role does runoff play in the water cycle?
Runoff is precipitation that did not get (infiltrated) absorbed into the soil or did not evaporate, and therefore, made its way from the ground surface into places that water collect. Runoff causes erosion and also carry chemicals and substances on the ground surface along to the rivers where the water ends up.
How does rainfall intensity affect runoff?
Rainfall intensity influences both the rate and the volume of runoff. An intense storm exceeds the infiltration rate of the soil by a greater margin than does a gentle rain; thus, the total volume of runoff is greater for the intense storm even though total precipitation for the two rains is the same.
Which of the following factors affect the runoff?
Meteorological factors affecting runoff: Rainfall intensity. Rainfall amount. Rainfall duration. Distribution of rainfall over the watersheds.
What are the factors affecting infiltration?
Factors that affect infiltration
- Precipitation.
- Soil characteristics.
- Soil moisture content.
- Organic materials in soils.
- Land cover.
- Slope.
- General hydrologic budget.
- Richards’ equation (1931)
Is runoff a process?
Surface runoff is the movement of water across the soil surface toward the stream channel. This process is more likely in areas with deep soil. Runoff, sometimes called quick response runoff, can refer to surface runoff only, but sometimes it is the combination of surface runoff plus interflow.
What are the two main components of runoff?
COMPONENTS OF RUNOFF:
- Direct rainfall over the stream:-
- Surface runoff or overland flow: –
- Subsurface flow or interflow:–
- Base flow, groundwater flow or Dry weather flow:-
What is an example of a runoff?
Runoff is defined as excess water draining away from land or buildings. The overflow of water that drains off of your driveway is an example of runoff. Dissolved chemicals, etc, included in such water. The runoff of nitrates is poisoning the lake.
What are some problems of early water runoff?
It is instead forced directly into streams, where erosion and siltation can be major problems, even when flooding is not. Increased runoff reduces groundwater recharge, thus lowering the water table and making droughts worse, especially for farmers and others who depend on water wells.
How can you prevent runoff?
Start with doing one of the actions on the following top 10 list:
- Maintain your car or truck.
- Wash your car at a commercial car wash rather than in the street or in your driveway.
- Drive less.
- Cut down on fertilizers, pesticides and herbicides.
- Remove part or all of your lawn.
What is direct runoff?
Water that flows over the ground surface directly into streams, rivers, or lakes. Also called storm runoff.
How do you find direct runoff?
Direct Runoff Formula For a given surface area such as a roof or yard, multiply the area by the inches of rainfall and divide by 231 to obtain the runoff in gallons.
How do you calculate runoff?
To calculate the runoff from any given rainfall:
- Take the dimensions of the footprint of your roof and convert them to inches. (So, a 50′ x 20′ roof is 600″ x 240″.)
- Multiply the roof dimensions by the number of inches of rainfall. (In this example, 600″ x 240″ x 1″ = 144,000 cubic inches of water.)
What is direct runoff hydrograph?
Direct runoff hydrograph resulting from a unit depth of excess rainfall occurring uniformly on a watershed at a constant rate for a specified duration. Unit pulse response function of a linear hydrologic system. Can be used to derive runoff from any excess rainfall on the watershed.
How do you get a direct runoff hydrograph?
- Separate the baseflow from the observed streamflow hydrograph in order to obtain the Direct Runoff Hydrograph (DRH).
- Compute the volume of Direct Runoff.
- Express VDRH in equivalent units of depth:
- Obtain a Unit Hydrograph by normalizing the DRH.
- Determine the duration D of the ERH associated with the UH obtained in 4.
What is relation between rain and runoff?
the rainfall-runoff relationship for any rainstorm depends on the dynamic interaction between rain intensity, soil infiltration and surface storage. Runoff occurs whenever rain intensity exceeds the infiltration capacity of the soil, providing there are no physical obstructions to surface flow.
How do you find the direct runoff hydrograph?
For example, if a rainfall of P1 inches occurs during a time interval of Δt, the total runoff hydrograph is P1 multiplied by the total unit hydrograph, which is the blue curve (PUH_1) in the figure below. If the rainfall stops after Δt, this is the direct runoff hydrograph.
How is streamflow hydrograph calculated?
The volume of water passing through a stream cross-section, VQ, over a specified duration, T, can be calculated by computing the area under the curve of a hydrograph, which is a plot of instantaneous streamflow, Q, against time, t (Figure 1). The y-axis of a streamflow hydrograph has units of L3t-1.
What is a 2 hour unit hydrograph?
To get a 2-hour UH, we want 1/2 inches/hour for two hours. So we have to divide the hydrograph ordinates by 2. We divided each hydrograph ordinate by two, resulting in a 2–hour Unit Hydrograph, i.e. One inch of direct runoff total from the 2 hour storm make a 1 hour UH.
Why are unit hydrographs useful?
A unit hydrograph shows the temporal change in flow, or discharge, per unit of runoff. In other words, how the flow of a stream will be affected over time by the addition of one unit of runoff. The unit hydrograph is a useful tool in the process of predicting the impact of precipitation on streamflow.
What is the difference between hydrograph and Hyetograph?
A hydrograph is graphically plot of discharge of a natural system for river versus time. A hyetograph is a plot of intensity of rainfall against the time interval it is usually represented buy a bar chart. 2.
What is S curve hydrograph?
S-curve, or S-curve hydrograph : A graph showing the summation of the ordinates of a series of unit hydrographs spaced at unit-rainfall duration intervals. It represents the hydrograph of unit rate of rainfall excess continued indefinitely.
What is S curve method?
In project management, an s-curve is a mathematical graph that depicts relevant cumulative data for a project—such as cost or man-hours—plotted against time. An s-curve in project management is typically used to track the progress of a project.
What is S curve?
In project management, an s-curve is a mathematical graph or illustration that properly illustrates the appropriate cumulative data for a project or task. This data can be the cost, or man-hours plotted against time. The reason why it’s called an S curve is not a very technical one.
What does a flow duration curve show?
The flow-duration curve is a cumulative frequency curve that show the percent of time specified discharges were equaled or exceeded during a given period. It combines in one curve the flow characteristics of a stream throughout the range of discharge, without regard to the sequence of occurence.
What is flow duration curve and its significance?
The flow duration curve is a plot that shows the percentage of time that flow in a stream is likely to equal or exceed some specified value of interest. The basic time unit used in preparing a flow-duration curve will greatly affect its appearance. For most studies, mean daily discharges are used.
What is strength duration curve?
Definition. noun. A graphical representation depicting the intensity of an electrical stimulus in relation to the duration (time) needed to stimulate excitable tissue.
What is mass duration curve?
A mass diagram is the plot of accumulated inflow (i.e. supply) or outflow (i.e. demand) versus time. From the past records, determine the hourly demand for all 24 hours for typical days (maximum, average and minimum). Calculate and plot the cumulative demand against time, and thus plot the mass curve of demand.