Water DemandM. Dikman Maheng

• Average Demand– demand drawn from annual records

• Specific Demand/Consumption– average demand per head per day (‘unit consumption per capita’)

Common Units

Water Demand

• For which purpose is the water used?– consumption categories: domestic, industrial, tourism, etc.

• Who is the user?– different cultures, education, age, climate,religion, technological process, etc.

• How valuable is the water?– scarce source (quantity/quality), bad access (no direct connection, fetching from a distance), low income of consumers, etc.

Consumption Categories

• Domestic Consumption– toilet flushing, bathing, showering, laundry, cooking,drinking, etc.

• Non-domestic Consumption– industry, agriculture, institution, offices, tourism, etc.

• Unaccounted for water (UFW)– leakage, meter under-reading, illegal connections, flushing, etc.– major ‘consumer’ in many systems (50% of total production)

Demand Patterns

Instantaneous Demands

Diurnal Demand Pattenrs

Night Demand Patterns

Evening Demand Patterns

Peak Factor

Weekly Demand Patterns

Monthly Demand Patterns

Demand Calculation

Demand Calculation

Demand Calculation

Demand Design

Hour Peak Water Quantities (m3/h)Factors Qwc Qwl Qd

1 0,440 205,52 51,90 257,412 0,440 205,52 51,90 257,413 0,450 210,19 51,90 262,094 0,730 340,97 51,90 392,875 1,350 630,56 51,90 682,466 1,670 780,03 51,90 831,937 1,690 789,37 51,90 841,278 1,530 714,64 51,90 766,549 1,360 635,23 51,90 687,1310 1,150 537,15 51,90 589,0411 1,070 499,78 51,90 551,6812 1,090 509,12 51,90 561,0213 1,090 509,12 51,90 561,0214 1,060 495,11 51,90 547,0115 1,240 579,18 51,90 631,0816 1,430 667,93 51,90 719,8317 1,410 658,59 51,90 710,4918 1,230 574,51 51,90 626,4119 0,930 434,39 51,90 486,2920 0,730 340,97 51,90 392,8721 0,530 247,55 51,90 299,45

Number of q Qwc, av g Leakage Equation Qd, av g 22 0,490 228,87 51,90 280,77

consum. (l/c/d) (m3/h) (%) 2.1/2.6 (m3/h) 23 0,460 214,86 51,90 266,7659000 190 467,08 10% 2,6 518,98 24 0,430 200,85 51,90 252,74

Average 1,000 467,08 51,90 518,98

Lesson 8-5Demand Calculation

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Average Water Consumption

Average Water Consumption

Hypothetical Example

Hypothetical Example

Demand Forecasting

• to be taken into account• projection of total consumption from historical growth trends• projection based on per capita consumption and population growth trends

for domestic category • forecast based on assessment of growth trends of other main consumer

categories (industry, tourism, etc.)• forecast based on development plans and programmes

Demand Forecasting

• population growth depends on• composition of the existing population by sex and age • fertility rates for different female age groups• mortality rates related to age and sex• rates of migration related to age and sex, to or from the area of interest

Demand Forecasting