1. Page 1

2. Page 2 GROUP MEMBERS Kush Poorunsing Aman Sahadeo Arshaad Jeedaran Nevin Sunassee Pamben Moonsamy Kishan Joorawon

3. Page 3 Population Forecasting Important process in the design of waste water treatment plants Factors affecting change in population:  Fertility/ Birth rate  Death rate  Migration

4. Page 4 Logistic Method Follows some logical mathematical relationship. has an S-shape combining a geometric rate of growth at low population with a declining growth rate as the population approaches some limiting value. Saturation population

5. Page 5 Equation - 1

6. Page 6 Equation - 2

7. Page 7 Equation - 3

8. Page 8 Census year Population 1851495 1861693 18711108 18811431 18912068 19013162 19114829 19216584 19318202 194411885 195213333 196218335 197224769 198333082 199034204 200035779 Example The data for population censuses from 1851 to 2000 for Island of Rodrigues is given below. Estimate the expected population in 2011.

9. Page 9 Census year Population 1851495 1861693 18711108 18811431 18912068 19013162 19114829 19216584 19318202 194411885 195213333 196218335 197224769 198333082 199034204 200035779 STEP 1 Three successive years, represented by t o, t 1, and t 2 are chosen such that they are equidistant from each other. t0t0 t1t1 t2t2

10. Page 10 Logistic Curve Plot

11. Page 11 Census year Population 1851495 1861693 18711108 18811431 18912068 19013162 19114829 19216584 19318202 194411885 195213333 196218335 197224769 198333082 199034204 200035779 STEP 2 The number of years from t o to t 1 and t 1 to t 2 is denoted by n. n=28 t0t0 t1t1 t2t2

12. Page 12 Census year Population 1851495 1861693 18711108 18811431 18912068 19013162 19114829 19216584 19318202 194411885 195213333 196218335 197224769 198333082 199034204 200035779 STEP 3 The population figures corresponding to t o, t 1, and t 2 are P o, P 1 and P 2 respectively through which the logistic curve is to pass. P0P0 P1P1 P2P2 n=28 t0t0 t1t1 t2t2

13. Page 13 CALCULATIONS - 1

14. Page 14 CALCULATIONS - 2

15. Page 15 CALCULATIONS - 3

16. Page 16 CONCLUSION Based on census reports, the population of Rodrigues in 2011 was 37,922 (Wikipedia) Estimated population with logistic method is 38420.8 1.31% deviation from actual value

17. Page 17 Advantages and Disadvantages Advantages  Longer projection period compared to simple geometric procedures  Gives a better approximation than other methods. Disadvantages  Mechanical process  Cannot predict decreasing population  Demographic and socioeconomic changes not considered  Requires a large number of observations covering a long period

18. Page 18 References Punmia, B.C, Arun, K.J., 2005. Water Supply Engineering. 2 nd ed. New Delhi: Laxmi Publications Annual Digest of Statistics 2011 [Online]. Available from: http://www.gov.mu/portal/goc/cso/file/AnnualDig estofStatistics2011.pdf Rodrigues [Online]. Available from: http://en.wikipedia.org/wiki/Rodrigues

19. Page 19 Thank You For Your Attention