JNTU
JNTU B.Tech III Year WATER RESOURCES ENGINEERING-I Previous Question Paper (September - 2021 - R13)
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Explain float type rain gauge with neat sketch.
Answer
A float-type rain gauge, also known as a natural-syphon rain gauge, is a recording-type instrument that provides a continuous plot of rainfall against time. It consists of a funnel that collects rainwater into a chamber containing a light, hollow float. As the water level in the chamber rises, the float moves upward, which in turn actuates a pen attached to a lever mechanism. The pen records the rainfall on a clockwork-driven drum wrapped with a chart.
When the chamber fills to a predetermined level, a syphon mechanism is triggered, rapidly emptying the chamber and returning the float to its zero position. This creates a vertical line on the chart, indicating the completion of a specific amount of rainfall. The resulting mass curve of rainfall allows for the determination of rainfall intensity at any given time.
Briefly explain the abstractions from rainfall and how do you calculate effective rainfall.
Answer
Abstractions from rainfall refer to the portion of precipitation that does not contribute to direct surface runoff. These include interception by vegetation, depression storage (water trapped in surface irregularities), evaporation from water surfaces, and infiltration into the soil. Infiltration is typically the most significant abstraction, representing the process by which water enters the soil profile.
Effective rainfall, also known as excess rainfall, is the portion of the total rainfall that results in direct surface runoff. It is calculated by subtracting all abstractions from the total storm rainfall. Mathematically, this is expressed as:
Where Pe is the effective rainfall, P is the total storm rainfall, and Φ (phi) represents the infiltration index, which is the average rate of rainfall above which the rainfall volume equals the runoff volume. In practice, the Φ-index is determined by trial and error such that the total volume of rainfall above the index equals the observed direct runoff volume.
Describe the hydrologic cycle along with a neat sketch.
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The shape of a catchment resembles a square of side 4 km. There are 5 rain gauge stations A, B, C, D and E within the watershed. With reference to an x-y coordinate axis having its origin at one of the corners of the square, the locations of the other 3 corners and the 5 rain gauge stations are (4, 0), (4, 4), (0, 4) and (1, 1),(3, 1),(3, 3),(1, 3) and (2, 2) respectively. The five stations A, B, C, D and E have reported storm rainfalls of 55, 76, 68, 40 and 63 mm respectively. Using Thiessen polygon method, compute the average depth of rainfall.
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What are the uses and applications of unit hydrograph.
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What is synthetic unit hydrograph? Explain how it is derived.
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From the topographical map of a drainage basin the following quantities are measured. A=3480 km2, L= 148 km and Lc = 74 km. The 12h unit hydrograph derived for the basin has a peak ordinate of 155 m3/s occurring at 40 h. Determine the coefficients Ct and Cp for the synthetic hydrograph of the basin.
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How do you determine the yield of an open well from pumping test.
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Write down the assumptions made in the theory of groundwater movement for steady radial flow to wells.
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Explain in detail the term well development.
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Explain any one method of well construction.
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A water course commands an irrigated area 800 hectares. The intensity of irrigation of rice in this area is 50%. The base period is 15 days and the total depth of water is 60cm. The useful rainfall falling in the field is 15cm. Find the duty of irrigation water for the crop on the field and also at the head of the water course, assuming the loss of water to be 20% in the water course. Also find the discharge required in the water course.
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Design an irrigation channel on Kennedy theory to carry a discharge of 14 cumecs. Take N =0.0225 and m =1. The channel slope of 1 in 5000 and side slope 0.5:1.
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