Lecture 3 Water Demand

1. Lecture 3Water Demand By: Eng. Ayman Afifi March 2009

2. Factors affect water consumption • Water cost • Country volume • Commercial and industrial system • Pressure in the network • Sewage system • Water supply system • Weather conditions and Climate • Tradition & habits • Counters

3. Water Consumption • Water consumption is initially split into domestic and non-domestic. The non-domestic consumption relates to the water used for industry and other commercial and public uses (shops, offices, schools, hospitals, etc). • Water demand is commonly expressed in cubic meters per hour (m³/h) or per second (m³/s), liters per second (l/s), or liters per capita per day (l / c /d or lpcpd).

4. Domestic Consumption • Domestic water consumption is intended for toilet flushing, bathing, showering, laundry, dishwashing and other less water intensive or less frequent purposes as cooking, drinking, gardening, car washing, etc. • In Gaza Strip, domestic water consumption varies from 80 l /c /d for some area to 120 l / c /d .

5. Domestic demand According to the PWA, The target water demand to be achieved in 2025 is 150 l / c /d. The planned domestic water consumption by PWA is summarized in the following table.

6. Residential consumption water • The world average water consumption is 280 L/C/day • For Middle East area, the average water consumption is 120 L/C/dayto 180 L/C/day

7. Non-domestic Consumption • Non-domestic or commercial water use occurs in industry, institutions and offices, tourism, etc. Each of these categories has its specific water requirements. - Industry • Water in industry can be used for various purposes: as a part of the final product, or for the maintenance of manufacturing processes (cleaning, flushing, cooling, etc). • The industrial consumption is largely dependable on the type of product and the technology used. • The industrial consumption is commonly expressed in liters per unit of product or raw material. The following table gives an indication for a number of industries.

8. Industrial demand

9. Commercial demand • Commercial consumption in restaurants, shops, schools and other institutions can be assessed as a total supply divided by the number of consumers (employees, pupils, patients, etc.). Accurate figures should be available from local records. • Commercial unit consumption are given in the following table :

10. Other Commercial demands

11. Agricultural water

12. Unaccounted for Water (UFW) • It’s an unavoidable component of water demand that is supplied ‘ free of charge ’. • Causes of UFW differ from case to case. Most often it is a leakage that appears due to improper maintenance of the network such as defective pipe joints, cracked and broken pipes, faulty valves and fittings. Other losses are related to the water that is supplied but not registered or paid for (under-reading of water meters, illegal connections, washing streets, flushing pipes, etc.)

13. How to measure UFW? • If meters are employed throughout a system, they can be the best source of data for determining customers consumption. Customers are typically billed based on a volumetric measure of usage, with meter readings taken on a monthly or quarterly cycle. Using these billing records the UFW water quantity can be easily calculated. • The UFW in the developing areas varies from 30 % to more than 50 % of the total water consumption. • According to PWA studies, the UFW is estimated as 30 % of the total water consumption up to year 2010, 25 % up to 2015 and 20 % up to 2020 and then will remain at the same percent.

14. Total consumption Total consumption is: A+B+C+D+E+F

15. Example نظام لتزويد المياه يخدم منطقة سكنية عدد أفرادها 1000 شخص بالإضافة إلى مصنع، على مدار السنة كان مقدار الاستهلاك الكلي لمياه الشرب 114,000 م3. قراءات العدادات بالنسبة للمصنع حددت استهلاك للمياه مقداره 38,000 م3. احسب متوسط الاستهلاك السكاني للفرد الواحد ثم حدد الاستهلاك اليومي المتوسط لكل نقطة استهلاك.

17. Water Quantities for Fire

18. In water network design for fire, the following criteria could be used: • The pressure at the fire hydrants (نقاط تغذية) is 20 m head with Q=60m3/hr • The time is two hour • Fire hydrant diameter is 10 cm • The water quantity for fire must be storage to fulfill the emergent need • The distance between the fire hydrant not more than 300 m in cities with middle density • The distance between the fire hydrant not more than 200 m in cities with high density • Fire numbers in the same time can be calculated by: P is population number in thousands

19. Design Period • Technical Lifetime : It represents the period during which it operates satisfactorily in a technical sense. • The suggested periods for the main distribution system components shown in the following table :

20. Estimation of design period Technical Concerns Economical Concerns

21. Design Period • Economic Lifetime : It represents the period of time for which the component can operate before it becomes more costly than its replacement. This lifetime is never longer than the technical lifetime; very often it is much shorter. • In practice, the design period is often the same as the economic lifetime. Moreover, a uniform design period will be chosen for all components; design periods of 20 – 25 years are typical for distribution systems. • An exception is the mechanical equipment in pumping stations, which has a lifetime of 10 – 15 years. Although water companies are sometimes able to successfully maintain pumps operating for longer than 30 years.

22. Demographic Data • Since the Water distribution network is usually designed to serve for at least 20 years, then the water consumption must be estimated at the end of the design period. To achieve that, the population of the served area should be known now and then. • The demographical data can be obtained from several sources, one of which is the Palestinian Central Bureau of Statistics ( PCBS ).

23. Estimation of population النمو السكاني الطبيعي نتيجة للتناسل يتراوح عادة مابين 1% إلى 7% حسب المجتمعات وعاداتها وتقاليدها، وعلى سبيل المثال في المجتمع الفلسطيني تتراوح معدل النمو الطبيعي من 3% إلى 6%، ففي مدينة كمدينة غزة يبلغ معدل النمو الطبيعي 4.5% ، بينما تبلغ الزيادة في معسكر جباليا حوالي 6%. بينما تبلغ النسبة كمتوسط في جميع أنحاء فلسطين 2.5%، ويوضح الجدول التالي توقع مركز الإحصاء الفلسطيني للسكان:

24. Population forecasting • Arithmetic increase method الطريقة الرياضية • This method assume that the population density increase uniformly Population after time t Present population population growth rate by each t unit This equation can be simplified to:

25. Uniform percentages Method طريقة ذات النسبة المنتظمة • (Geometric Increase) population growth rate by each t unit • Predicted curves Method طريقة المنحنيات التوقعية • (curvilinear method) population growth rate by each t unit

26. Example • Estimate the population number after 30 year, if the initial population number is 100,000. the population growth rate is 3% Method 1 Method 2 Method 3

27. Population Saturation and urban planning • Master Plane • LandUse • General laws • Although the population forecasting methods gives the population at the end of the design period, the maximum possible population is also estimated according to the number of apartment and stories per unit area and the maximum family members. • The Saturation population can be determined using the Master plan for the area and its general laws. • The minimum of the two values is taken in consideration when the network is designed.

28. Example A residential area 100,000 m² and population of 4200 capita has the following Master Plan : 25 % of the total area is for Streets. 5 % of the total area is for green Areas. 70 % of the total area is for buildings. 60 % of the building area is for building and the 40 % for the If the family living there consists of members and the average apartment area is 150 m², Calculate the Population needed for designing a water distribution system to serve that area for 25 years if you are given that the growth rate of the population = 3 %.

29. Cont. example 1. Population Forecasting : Pt = P0 (1+k)n Pt = 4200 (1+0.03)25 Pt = 8794 capita • Saturation Population : The Population = 7000 capita

30. Topographical Studies Surveying maps should be prepared in which 3 items must be presented : • Contour Lines. • Master Plan ( Land Use ). • Location of water resources .

31. QUESTIONS