WATER AVAILABILITY

Umboro

DURATION CURVE

Discharge a m3/s occur along observation period (100%) Discharge b m3/s only occur half of observation period (50%)

Depenable Discharge

Storage volume

Release volume

Depenable discharge

Q (m3/s)

Calculation of Duration curve

Daily Q (m3/s) Frequency Total Frequency % Cumulative

5 22 365 100

10 46 343 94

15 118 297 81

20 84 179 49

25 42 95 26

30 34 53 14.5

40 14 19 5.2

50 5 5 1.4

365

Duration Curve

Mass curve

Hydrograph (left) and Mass curve (right)

Mass Curve Calculation T (hour) Q (m3/s) V (10^3 m3 Vcum (10^3 m3)

0 4 0 0

1 10 25.2 25.2

2 15 45.0 70.2

3 25 72.0 142.2

4 20 81.0 223.2

5 18 68.4 291.6

. . . .

. . . .

. . . .

Reservoir Design Example

• Water demand of a city is function of percentage daily

maximum water demand.

• Water supplied by continue pump station from 08.00 am

to 6 pm.

Time (hour) Water demand (% max daily water demand)

Water supply (% max daily water demand)

0-1 2 -

1-2 1 -

2-3 0.5 -

3-4 0.5 -

4-5 0.5 -

5-6 2.5 -

6-7 3 -

7-8 3 -

8-9 4 10

9-10 6 10

10-11 4 10

11-12 7.5 10

Time (hour) Water demand (% max daily water demand)

Water supply (% max daily water demand)

11-12 7.5 10

12-13 11 10

13-14 8.5 10

14-15 7 10

15-16 5 10

16-17 5 10

17-18 5 10

18-19 5 -

19-20 5 -

20-21 7 -

21-22 5 -

22-23 2 -

23-24 2 -

Time (hour) Water demand (% max daily

water demand)

Water supply (% max daily

water demand)

Different Cummulative different

0-1 2 - -2 -2

1-2 1 - -1 -3

2-3 0.5 - -0.5 -3.5

3-4 0.5 - -0.5 -4

4-5 0.5 - -0.5 -4.5

5-6 2.5 - -2.5 -7.0

6-7 3 - -3 -10

7-8 3 - -3 -13 *

8-9 4 10 +6 -7

9-10 6 10 +4 -3

10-11 4 10 +6 +3

Time (hour) Water demand (% max daily

water demand)

Water supply (% max daily

water demand)

Different Cummulative different

11-12 7.5 10 +2.5 +5.5

12-13 11 10 -1 +4.5

13-14 8.5 10 +1.5 +6.0

14-15 7 10 +3 +9.0

15-16 5 10 +5 +14.0

16-17 3 10 +7 +21.0

17-18 5 10 +5 +26*

18-19 5 - -5 +21

19-20 5 - -5 +16

20-21 7 - -7 +9

21-22 5 - -5 +4

22-23 2 - -2 +2

23-24 2 - -2 0

RESERVOIR VOLUME VOLUME RESERVOIR = 13 + 26 = 39 % DAILY MAX

WATER DEMAND

Mass inflow and mass outflow