Hydrology & Irrigation

Q. A deep reservoir had the following average values of climatic parameters during a week:
(i) Saturation vapour pressure = 17.54 mm Hg
(ii) Relative humidity = 50%
(iii) Wind velocity at 1.0 m above ground surface = 16 kmph
An ISI standard pan at the site has pan coefficient 0.80. If this pan indicates an evaporation of 70 mm in a week, estimate the error in the result of Meyer's method relative to pan evaporation measurements.
$[\text{Take}{k}_m=0.36]$

1. 11%
2. 4.6%
3. 6.5%
4. 9%

Q. If the wind velocity at a height of 9 m is measured as 50 km/h, the velocity at a height of 0.5 m above the ground can be expected to be, in km/h about

1. 18
2. 28
3. 33
4. 43

Q. Which of the following empirical methods/formulae can be used to estimate the evaporation loss from a water course?

i) Muskingum formula

ii) Mayer's formula

iii) Fitzgerald's formula

iv) Thiem's formula

1. (i) and (ii)
2. (i) and (iv)
3. (ii) and (iii)
4. (iii) and (iv)

Q. Maximum vertical compressive stress acting at the base of a gravity dam is found to be 240 tonnes per square meter. Sum of vertical and horizontal forces acting on the dam are calculated as 4600 tonnes and 400 tonnes per meter length respectively. If the base width of the dam is 30 m, the resultant force will be acting with an eccentricity of ____

1. 1.8 m
2. 2.8 m
3. 4.3 m
4. 5.1 m

Q. At the base of a gravity dam section, the vertical stress at toe was found to be 3.6 MPa. If the downstream face of dam has slope of 0.707 H : 1 V and if there is no tail water, then the maximum principal stress at the toe of the dam is

1. 3 MPa
2. 4.5 MPa
3. 3.5 MPa
4. 5.4 MPa

Q. Following data were obtained from the stability analysis of a concrete gravity dam:
Weight of the dam = 6500 tonnes/m
Uplift force = 1500 tonnes/m
Base width of dam = 60 m
The resultant force acts at 25 m from the toe.
The maximum vertical stress on the foundation soil will be

1. $291.67t/m^2$
2. $125t/m^2$
3. $41.67t/m^2$
4. $162.5t/m^2$

Q. The field capacity of a certain soil is 20% and the moisture content of the soil before irrigation is 10%. What is the approximate depth upto which the soil will be wetted with an application of 50 mm of water?
[Take dry unit weight of soil as $15kN/m^3$ and unit weight of water as $10kN/m^3$]

1. 250 mm
2. 333 mm
3. 367 mm
4. 433 mm

Q. The state of the soil when plants fail to extract sufficient water for their requirements is____.

1. Maximum saturated point
2. Permanent wilting point
3. Ultimate utilization point
4. None of these

Q. For an irrigated field having: Field capacity = 30%, Permanent wilting point = 10%, Permissible depletion of available moisture = 40%, Dry weight of soil = 14.70 kN/m${}^3$, Unit weight of water = 9.8 kN/m${}^3$ and Effective rainfall = 30 mm, what is the net irrigation requirement per meter depth of soil?

1. 300 mm
2. 150 mm
3. 120 mm
4. 90 mm

Q. A soil sample has an exchangeable sodium percentage of 16%, its electrical conductivity is 3.2 milli-Mohs/cm and pH of 9.5. How is the soil classified ?

1. Saline soil
2. Saline-alkaline soil
3. Alkaline soil
4. None of the above