10 Questions
What is the main purpose of using a double ring infiltrometer?
To avoid lateral movement of water
What is a limitation of the double ring infiltrometer method?
The soil gets disturbed while inserting the cylinder
What is the advantage of using the double ring infiltrometer method compared to the basin infiltrometer?
It requires relatively little water
What is the purpose of the outer cylinder in the double ring infiltrometer?
To fill with water to the same height as the inner cylinder
What is the hydrograph method used for?
To determine the infiltration rate
What is the result of subtracting the amount of surface runoff from the amount of rainfall in the hydrograph method?
The infiltration rate
What is the purpose of separating the base flow from the discharge hydrograph?
To obtain the direct runoff hydrograph
What is the direct runoff hydrograph (DRH) used for?
To account for the direct surface runoff
What is the advantage of using the double ring infiltrometer method compared to other methods?
It provides the most accurate results
What is the limitation of using the hydrograph method?
It neglects evaporation
Study Notes
Rainfall Simulators
- Used to measure infiltration rates by simulating rainfall on a small plot of land (2m x 4m) with nozzles producing raindrops from a height of 2m
- Various intensities and durations of rainfall can be simulated
- Surface runoff is measured and infiltration rates are calculated using water budget equations
Sprinkler Infiltration Method
- Similar to irrigation by sprinkler, where the rate of application is equal to or more than the infiltration rate of the soil
Basin Ponding Method
- Similar to the cylinder method, but uses a circular or rectangular basin instead
- Used in Vertisols where infiltration rates are low and basin or border irrigation is practiced
- Water is introduced into the basin to a depth of 12cm and the water level is recorded using a hook gauge
Factors Affecting Infiltration
- Surface roughness and sealing can affect infiltration rates
- Heavy rainfall can result in little infiltration before runoff
- Steady rainfall can result in more water infiltrating into the soil before runoff
Single Ring Infiltrometer
- Consists of a single cylinder with a diameter of 30cm and a depth of 25cm
- Infiltration is measured by pouring water into the cylinder and measuring the quantity of water added over time
- Lateral movement of water is not restricted, resulting in large variations in infiltration rates
Double Ring Infiltrometer
- Consists of two concentric cylinders to reduce lateral movement of water
- Water is filled in the outer cylinder to the same height as the inner cylinder to avoid lateral flow
- Provides more accurate results, but can disturb the soil and cause unnatural seepage
Hydrograph Methods
- Determine infiltration rates by analyzing rainfall and runoff data from a catchment area
- Infiltration rate is obtained by subtracting surface runoff from rainfall
- Total volumes of infiltration and other losses can be obtained from a discharge hydrograph
This quiz covers the concept of rainfall simulators used in civil engineering to measure infiltration and surface runoff rates. It discusses the design and functionality of rainfall simulators.
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