NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA -769008

MID-SEMESTER EXAMINATION
SESSION: 2023-2024 (Autumn)
B. Tech. 5th Semester
Subject Code: CE3401 Subject Name: Water Resources Engineering Dept. Code: CE
No. of Pages: 02 (Two) Full Marks : 30 Duration: 2 Hours
Q.
Particulars (Answer all the question) Marks
No.
1. a) What do you mean by Catchment? Explain with the help of a diagram. 1
b) Kartik used to jog around the Naga Pond. One day, while running, he came across a wooden stick, he 3
made a mark on the stick and threw it into the Naga Pond. After a month, when he retrieved the stick, he
noticed that the water level of the Naga Pond had risen by 60 cm. After some initial investigation and
inquiries, he discovered that the outflow (in m3/s) from the lake exceeded the inflow (in m3/s) from
surface runoff sources by 10%. Additionally, during that month, while examining various rainfall
sources, Kartik learned that the lake had received 150 mm of rainfall, and the estimated evaporation
from the Naga pond's surface was 6.00 cm. Write the water-budget equation for the lake and calculate
the average outflow (in m3/s) and inflow (in m3/s) from the lake for the month? The average surface area
of the lake can be assumed to be 5000 hectares. There is no contribution to or from groundwater storage
in this scenario. Also, if the inflow is changed to 10 m3/s, and the relation between inflow and outflow is
same then, what will be the change in elevation of the Naga Pond for the same month?

2. a) After completing his bachelor's degree, Atul has established himself as a successful engineer. As an 2
alumnus and senior of NIT Rourkela, a current final-year student in the Civil Engineering program
approached Atul for access to rainfall data. However, before sharing this data with his junior peers, Atul
intends to verify its consistency. Describe the procedure Atul would employ to assess the consistency of
the rainfall data?
Surbhit was conducting his BTP project, focusing on the analysis of the NITR campus's total rainfall 3
over the past three decades. During the analysis, he detected irregularities in the data from one of the
rainfall stations and decided to rectify the data for that specific station. While plotting a graph illustrating
the annual rainfall data for station M against the average annual rainfall values for a cluster of
neighboring stations, Surbhit made an intriguing observation. He observed that the best-fit line for the
graph between 1950-68 adhered to the equation y=0.88x+ 918. However, post-1968, the plot exhibited a
different trend, following the equation y=1.03x + 12.5.
Data for the annual rainfall at station M, as well as the average annual rainfall values for ten neighboring
stations are provided below. Adjust the recorded data at station M and determine the mean annual
precipitation for station M.
Annual
Annual Rainfall
Rainfall AnnualRainfall of AnnualRainfall of the
Year Year of Station M
of Station M the group (mm) group (mm)
(mm)
(mm)
1950 676 780 1965 1244 1400
1951 578 660 1966 999 1140
1952 95 110 1967 573 650
1953 462 520 1968 596 646
1954 472 540 1969 375 350
1955 699 800 1970 635 590
1956 479 540 1971 497 490
1957 431 490 1972 386 400
 1958 493 560 1973 438 390
1959 503 575 1974 568 570
1960 415 480 1975 356 377
1961 531 600 1976 685 653
1962 504 580 1977 825 787
1963 828 950 1978 426 410
1964 679 770 1979 612 588

3. a) What do you mean by return period? What do you mean by hyetograph? 1

b) The watershed of a stream has five raingauge stations inside the basin. When Thiessen polygons were 2
constructed, three more stations lying outside the watershed were found to have weightages. The
details of Thiessen polygons surroundings each raingauge and the recordings of the raingauges in the
month of July 2012 are given below:

Raingauge station A B C D E F G H
Thiessen Polygon area (km2) 720 1380 1440 1040 900 2220 419 1456
Rainfall (mm) (July 2012) 135 143 137 128 102 115 99 101
Stations B, D and F are outside the watershed. Determine the average depth of rainfall on the watershed
in July 2012 by (i) arithmetic mean method, and (ii) Thiessen Polygon method.
4. a) Explain briefly the evaporation process. Discuss the factors that affect the evaporation from a water 2
body.
b) At the Hirakud reservoir on the Mahanadi River, the following climatic data were observed. Estimate 3
the mean monthly and annual evaporation from the reservoir using Meyer’s formula. Take, Km = 0.36

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Saturated
Vapor
pressure (mm 10.9 13.4 18.3 26.7 33.7 38.8 32.8 29 28.3 22.1 16.4 11.8
of HG)

Relative
humidity (%) 85 82 71 48 41 52 78 86 82 75 77 73
Wind velocity
at 2 m above 4 5 5 5 7.8 10 8 5.5 5 4 3.6 4
GL (km/h)

𝒖
𝑬𝑳 = 𝑲𝒎 (𝒆𝒘 − 𝒆𝒂 ) (𝟏 + 𝟏𝟔𝟗+
5. a) Distinguish between 3
(i) Infiltration capacity and infiltration rate
(ii) Actual and potential evapotranspiration
(iii) Field capacity and permanent wilting point
b) Rainfall over a basin in three consecutive hours are 4 cm, 5 cm and 3 cm respectively. Estimates 4
surface runoff from the basin assuming negligible surface retention and evaporation losses. The
infiltration loss can be estimated using the following Horton's equation
–2.5t
fp = 1.2 + 4.2e
Where, fp is in cm/h and t is in hours.
6. Prachi and Sahil were collaborating on their BTP project. As part of their research, they collected a small 6
soil sample from the DTS, which they stored in a tube. The tube had a cross-sectional area of 40 cm² and
was filled with the soil sample. However, due to a time constraint, they decided to temporarily store the
sample in hostel. In haste, Prachi placed the sample horizontally instead of vertically. Assuming that the
open end of the tube was initially saturated, they observed that after 15 minutes, 100 cm³ of water had
infiltrated. Given that the saturated hydraulic conductivity of the soil is 0.4 cm/h, determine the amount
of infiltration that would have occurred in 30 minutes if Prachi had initially positioned the soil column
upright with its upper surface saturated.