Engineering Hydrology
Exam Duration: 45 Mins Total Questions : 30
A catchment has an area of 150 ha and a runoff/rainfall ratio of 0.40.If due to a 10 cm rainfall over the catchment a stream flow at the catchment outlet lasts for 10 h, the average stream flow in the period is
- (a)
1.33 m3/s
- (b)
16.7 m3/s
- (c)
100 m3/min
- (d)
\(6\times { 10 }^{ 4 }{ m }^{ 3 }/h\)
From isohyets maps study, at Roorkee a maximum rainfall depth of 250 mm in 12 h rainfall equal to or greater than 250 mm occuring at least Roorkee at least once in 50 yr is
- (a)
0.99
- (b)
0.64
- (c)
0.61
- (d)
0.34
The probability that a 100 yr flood is equalled or exceeded at once in 100 yr is
- (a)
99%
- (b)
64%
- (c)
36%
- (d)
1%
The rainfall during three successive 2 h periods are 0.5 cm, 2.8 em and 1.6 cm. The surface runoff resulting from this storm is 3.2 cm. The \(\phi \)index value of this storm
- (a)
0.20 cm/h
- (b)
0.28 cm/h
- (c)
0.30 cm/h
- (d)
0.80 cm/h
A 3 h storm on a small drainage basin produced rainfall intensities of 3.5cm/h, 4.2 cm/h and 2.9 cm/h in successive hours.If the surface runoff due to the storm is 3 cm, then the value of \(\phi \)index will be?
- (a)
2.212 cm/h
- (b)
2.331 cm/h
- (c)
2.412 cm/h
- (d)
2.533 cm/h
A storm with 14 cm precipitation produced a direct runoff of 8 cm.The time didtribution of the storm is as shown in the table below.
Time from start(h) | Incremental Rainfall(cm) |
1.0 | 1.0 |
2.0 | 2.0 |
3.0 | 2.8 |
4.0 | 3.3 |
5.0 | 2.5 |
6.0 | 1.8 |
7.0 | 0.6 |
What is the \(\phi \)-value of the storm?
- (a)
0.5 cm/h
- (b)
0.7 cm/h
- (c)
0.8 cm/h
- (d)
0.9 cm/h
A 6 h unit hydrograph of a catchment is triangular in shape with a base width of 64 h and peak discharge of 20 m3/s.If a 0.5 cm rainfall excess occurs in 6 h in that catchment, the resulting surface runoff hydrograph will have
- (a)
a base of 128 h
- (b)
a base of 32 h
- (c)
a peak of 40 m3/s
- (d)
a peak of 10 m3/s
For a catchment with an area of 360 km2 and the equilibrium discharge of S-curve obtained by 4 h unit hydrograph in m3/s is
- (a)
250
- (b)
90
- (c)
\(90\times { 10 }^{ 4 }\)
- (d)
\(250\times { 10 }^{ 4 }\)
A 4 h unit hydrograph of a basin can be approximated as a triangle with a base period of 48 h and peak ordinate of 300 m3/s.What is the area of the catchment basin?
- (a)
7776 km2
- (b)
5184 km2
- (c)
2592 km2
- (d)
1294 km2
The yield of a well depends upon
- (a)
permeability of soil
- (b)
area of aquifer opening into wells
- (c)
actual flow velocity
- (d)
All the above
The performance of a well is measured by
- (a)
specific capacity
- (b)
specific yield
- (c)
storage coefficient
- (d)
permiability coefficient
An unconfined aquifer of porosity 30%, permeability 35 m/day and specific yield of 0.20 has an area of 100 km2 .If the water table falls by 0.25 m during a drought, the volume of water lost from storage in million cubic metre is
- (a)
2.0
- (b)
5.0
- (c)
1.0
- (d)
4.0
In an artesian aquifer, the draw down in two observation wells, located at distances of 100 m and 300 m, were found to be the same after one hour and x hours respectively.The value of x in such a case is
- (a)
\(\frac { 1 }{ 9 } h\)
- (b)
3 h
- (c)
9 h
- (d)
27 h
If the specific capacity of a well is 1.66 L/s,then the discharge from this well under a depression head of 3m will be
- (a)
1.166 L/s
- (b)
3.5 L/s
- (c)
10.5 L/s
- (d)
11.66 L/s
A watershed got transformed from rural to urban area over a period of time.The effect of urbanisation on storm runoff hydrograph from the watershed is to
- (a)
decrease the volume of runoff
- (b)
increase the time to peak discharge
- (c)
decrease the time base
- (d)
decrease the peak duscharge
A flood wave with known inflow hydrograph is routed through a large reservoir.The outflow hydrograph will have
- (a)
attenuated peak with reduced time base
- (b)
attenuated peak with increased time base
- (c)
decrease the time base
- (d)
decrease the peak discharge
When the outflow from a reservoir is uncontrolled as in a freely operating spillway, the peak of outflow hydrograph occurs at
- (a)
the point of intersection of and inflow outflow hydrograph
- (b)
a point, after the intersection of the inflow and outflow hydrographs
- (c)
the tail of inflow hydrographs
- (d)
a point, before the intersection of inflow and outflow hydrographs.
The direct runoff hydrograph obtained from a catchment is triangular in shape and has a base period of 80 h.The peak flow rate is 30 m3/s and catchment area is 86.4 km2.The rainfall excess that resulated the above hydrograph is
- (a)
5 cm
- (b)
8 cm
- (c)
10 cm
- (d)
16 cm
During a 6 h storm, the rainfall intensity was 0.8 cm/h on a catchment of area 8.6 km2.The measured runoff volume during this period was 256000 m3.The total rainfall was lost due to infiltration, evaporation and transpiration(in cm/h) is
- (a)
0.80
- (b)
0.304
- (c)
0.496
- (d)
0.696
The average rainfall for a 3 h duration storm is 2.7 cm and the loss rate is 0.3 cm/h. The flood hydrograph has a base flow of 20 m2/s and produces a peak flow of 210 m2 /s. The peak of 3 h unit hydrograph is
- (a)
125.30 m3/s
- (b)
105.50 m3/s
- (c)
77.77 m3/s
- (d)
70.37 m3/s
A catchment consists of 35 % area with runoff coefficient 0.45 with the remaining 65% area with runoff coefficient 0.55. The equivalent runoff coefficient will be
- (a)
0.5005
- (b)
0.515
- (c)
0.50
- (d)
0.450
The area between the two isohyets 45 cm and 55 cm is 100 km 2 and that between 55 cm and 65 cm is 150 km 2. What is the average depth of annual precipitation over the basin of 250 km 2?
- (a)
50 cm
- (b)
52 cm
- (c)
56 cm
- (d)
60 cm
The Horton's infiltration equation for a basin as given by
f=4+10e-2t, Where (f in mm/h and t in h)
If a storm occurs on this basin with an intensity of more than 20 cm/h, then the depth of infiltration for the first 30 min will be
- (a)
14 cm
- (b)
4 cm
- (c)
5.16 cm
- (d)
10 cm
When 3.68 million m3 of water was pumped out from an unconfined aquifer of 6.2 km 2 aerial extent. The water table was observed to go down by 2.6 m. The specific yield of the aquifer for will be
- (a)
19.5 %
- (b)
12.8 %
- (c)
15.5 %
- (d)
22.8 %
What should be the diameter of an open well to give a safe yield of 4.8 L/s? Take working head as 3.57 m and soil constant c = 0.5 h -1.
- (a)
2.5 m
- (b)
1.4 m
- (c)
3.4 m
- (d)
4.6 m
The direct runoff hydrograph was found to have a peak ordinate at 10 h after the commencement of the effective rainfall and a base period of 100 h. The duration of the storm was
- (a)
Less than 10h
- (b)
between 10h and 100h
- (c)
equal to 100h
- (d)
more than 100h
1 h triangular unit hydrograph of a watershed has the peak discharge of 60 m3/s at 10 h and time base of 30 h. The Φ- index is 0.4 cm/h and base flow is 15 m3/s
The catchment area of the watershed is
- (a)
3.24 km2
- (b)
32.4 km2
- (c)
324 km2
- (d)
3240 km2
1 h triangular unit hydrograph of a watershed has the peak discharge of 60 m3/s at 10 h and time base of 30 h. The Φ- index is 0.4 cm/h and base flow is 15 m3/s
If there is rainfall of 5.4 cm in 1 h, the ordinate of the flood hydrograph at 15 the hour is
- (a)
225 m3/s
- (b)
240 m3/s
- (c)
249 m3/s
- (d)
258 m3/s
Ordinates of a 1 h unit hydrograph at 1 h intervals, starting from t=0 are 0,2,6,4,2,1 and 0 m3/s
Ordinate of a 3 h unit hydrograph for the catchment at t=3 h is
- (a)
2.0 m3/s
- (b)
3.0 m3/s
- (c)
4.0 m3/s
- (d)
5.0 m3/s
The peak of flood hydrograph due to a 3 h duration isolated storm in a catchment is 270 m3/s. The total depth of rainfall is 5.9 cm assuming an average infiltration loss of 0.3 cm/h and a constant of this base flow of 20 m3/s
The peak of the 3 h unit hydrograph of this catchment is
- (a)
1250 m3/s
- (b)
250 m3/s
- (c)
50 m3/s
- (d)
270 m3/s