Example Final Exam Questions-Hydrology

Example Final Exam Questions: Space Kuching Rainfall Analysis

1. Rainfall record from 1960 to 1995 as shown in the Table Q1 a) Determine the average annual rainfall the the given period b) Plot rainfall depth against time c)

Compute the moving average for 3 years and 5 years and plot the moving average in the same graph

d) Using the residual mass curve determine the drought and wet period. 2. Coordinates of several rainfall stations are indicated in Table Q2. Raingauge K requires the infilling of missing rainfall data based on quadrant method. a) Plot the location of raingauges in a graph paper b) Decide and draw the quadrant. c)

Compute the distance from selected station from station K

d) Estimate the rainfall depth at station K 3. Records of annual rainfall for station X and annual average rainfall for neighbouring 10 station for 30 years are shown in Table Q3. It is suspected that the considerable change has taken place related to development and environment around station X. a) Plot the double mass curve and identify the time of regime change. b) Adjust the rainfall data Plot two graphs of double mass curve with the first from 1961 to 1 990 and the second from 1990 to 1961 Infiltration

4. Compute and construct rate of infiltration (cm/jam) and infiltration depth resulting from the 2 hours rainfall for time interval Δt 0.5 h. Also determine the total infiltration depth (in cm) and excess rainfall (in cm/hr). Given: 2 hours rainfall with intensity 1.8 cm/h Initial infiltration rate f o = 1.5 cm/h Constant infiltration rate f c = 0.38 cm/h Coefficient of permeability , k = 0.76 h

-1

Adopt time interval 0.5 h. Streamflow Analysis b

5. The rating curve be expressed as Q = aH  where 3

Q = discharge (m /s) H = height of water level (m) a & b = constants a) Plot the graph of height of water level against discharge and determine the height of water level at zero discharge. b) Determine the constants a & b c)

Write the rating curve equation

Water Balance Equation

6a)

2

From the hydrologic records over 35 years on the drainage basin of area 550 km , the average annual rainfall is estimated as 150 cm and the average annual runoff 30 2

cm. A reservoir in the basin, having an average surface area 18 km , is planned at the basin outlet to collect available runoff for supplying water to nearby community. The annual evaporation over the reservoir surface is estimated 120 cm. There is no groundwater leakage or inflow to the basin. Determine the available average annual withdrawal from the reservoir for water supply.

 Answer:

 Precipitation over the river basin, P = 150 cm x 550 km

2

Evaporation from the reservoir open water surface, ET = 120 cm x 18 km

2

2

Available runoff from average baseflow, Q = 30 cm x 5 50 km No groundwater leakage, ∆G = 0

;

No inflow to the basin, I = 0

∆S = available average annual withdraw

  (  )  (  )  (       )    

  ()        

(b)

A reservoir has the following inflows and outflows for the first three months of the year as illustrated in Table 6b. If the storage at the beginning of April is 3

750 m , determine the storage at the end of May, June and July. Inflows and outflows in unit m3. Table 6b Month

April

May

June

July

Inflows

58

28

60

48

Outflows

80

54

45

52

 Answer:

Table 6b Month

April

May

June

July

Inflows

58

28

60

48

Outflows

80

54

45

52

Storage (Beginning of month)

750

728

702

717

Inflow  –  Outflow

-22

-26

+15

-4

Storage (End of month)

728

702

717

713

Infiltration and Evapotranspiration

Q7.

(a)

Define  -Index in the infiltration theory. Discuss on the variation of  - Index of a watershed that undergo urbanization process.

(b)

A two hour rain fell on a catchment of 1,000 Hectares. The intensity of the rainfall is tabulated in Table Q1. If the value of  -index for the catchment is 3.0 3 cm/hour, calculate the volume of surface runoff and the infiltrated wat er in m

Table Q7: Two hour rainfall intensity Time (min) Rainfall intensity (cm/hr)

(c)

0-40

40-60

60-80

80-100

100-120

2.0

2.5

6.5

12.0

4.0

A swimming pool has a length of 50 m and a width of 25 m. During July the Class A pan evaporation reading is 17.0 cm. If the pan coefficient is 0.80, what is the monthly water volume loss in m 3 due to evaporation.