How to analyse rainfall data - CWC

1 World Bank & Government of The Netherlands fundedTraining module # SWDP - 12 How to analyse rainfalldataNew Delhi, February 2002 CSMRS Building, 4th Floor, Olof Palme Marg, Hauz Khas,New Delhi 11 00 16 IndiaTel: 68 61 681 / 84 Fax: (+ 91 11) 68 61 685E-Mail: Consultants BV & DELFT HYDRAULICS withHALCROW, TAHAL, CES, ORG & JPSH ydrology Project Training Module File: 12 How to analyse rainfall Version 17/09/02 Page 1 Table of text10 hydrology Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 21. Module contextWhile designing a training course, the relationship between this module and the others,would be maintained by keeping them close together in the syllabus and place them in alogical sequence.

2 The actual selection of the topics and the depth of training would, ofcourse, depend on the training needs of the participants, their knowledge level and skillsperformance upon the start of the Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 32. Module profileTitle:How to analyse rainfall dataTarget group:Assistant hydrologists, Hydrologists, data Processing CentreManagersDuration:Three sessions of 60 minObjectives:After the training the participants will be able to:1. Carry out prescribed analysis of rainfall dataKey concepts: Homogeneity of rainfall data sets Basic statistics Annual maximum & exceedence series Fitting of frequency distribution Frequency and duration curves Intensity-duration-frequency curves Depth-area-duration curvesTraining methods:Lecture, softwareTraining toolsrequired:Board, computerHandouts:As provided in this moduleFurther readingand references: hydrology Project Training Module File: 12 How to analyse rainfall Version Feb.

3 2002 Page 43. Session planNoActivitiesTimeTools1 General Analysis of rainfall data3 minOHS 12 Checking data homogeneity General3 minOHS of basic statistics Basic statistics Example 3 (a) Statistics for monthly rainfall series Example 3 (b)- Plot of frequency distribution4 minOHS 3 OHS 4 OHS of frequency distributions General Available distribution Analysis results Example 4 (a) Basic statistics Example 4 (b) Goodness of fit test Example 4 (c) Annual maximum of daily data series Example 4 (d) Annual maximum of monthly data series Example 4 (e) Annual data series10 minOHS 6 OHS 7 OHS 8 OHS 9 OHS 10 OHS 11 OHS 12 OHS curves Definition Frequency curves Example (a) Frequency curves Definition Duration curves Example (b) Duration curves Definition Average duration curves Example (c)

4 Average duration curve10 minOHS 14 OHS 15 OHS 16 OHS 17 OHS 18 OHS IDF-curves Definition and computational procedure Illustration of first step in computational procedure Illustration of second step in computational procedure Illustration of third step in computational procedure Mathematical forms of IDF-curves T = 50 years Iso-pluvials for 1-hour maximum rainfall T = 50 years Iso-pluvials for 24-hour rainfall Definition of partial duration series Annual maximum and annual exceedance series Conversion of return period between annual maximum andannual exceedance series Ratio of return periods for annual exceedance and annualmaximum series Example (a) EV1-fit to hourly rainfall extremes Example (b) EV1-fit to 1-48 hr rainfall extremes Example (c) IDF analysis tabular output Example (d) IDF analysis tabular output continued Example (e) IDF curves linear scale (ann.)

5 Maximumseries) Example (f) IDF curves log-log scale (ann. maximumseries) Example (g) IDF analysis for ann. exceedances, tabu-lar output45 minOHS 20 OHS 21 OHS 22 OHS 23 OHS 24 OHS 25 OHS 26 OHS 27 OHS 28 OHS 29 OHS 30 OHS 31 OHS 32 OHS 33 OHS 34 OHS 35 OHS 36 OHS 37 hydrology Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 5 Example (h) IDF curves linear scale (ann. exceedan-ces) Example (i) IDF curves log-log scale (ann. exceedan-ces) Example (j) Generalisation of IDF curves inmathematical formula Example (k) Test on quality of fit of formula to IDF-curvesOHS 38 OHS 39 OHS 40 OHS analysis Definition and computational procedure Example (a) Division of basin in zones Example (b) cumulation of rainfall per zone Example (c) - cumulation of rainfall in cumulated zones Example (d)

6 Drawing of DAD-curves Areal reduction factor, definition and variability Example of ARF s for different durations Time distribution of storms, pitfalls Example of time distribution of storms15 minOHS 42 OHS 43 OHS 44 OHS 45 OHS 46 OHS 47 OHS 48 OHS 49 OHS 50 Exercise Compute basic statistics for a monthly rainfall data series Use normal distribution fitting for maximum monthly rainfalldata series Derive frequency duration curves for a ten daily rainfall dataseries Derive IF-curves for various durations Derive IDF-curves for annual maximum series Derive IDF-curves for annual exceedances Repeat IDF analysis for other stations in Bhima basin Fit regression equation to IDF-curves10 min10 min10 min10 min5 min5 min20 min20 minHydrology Project Training Module File.

7 12 How to analyse rainfall Version Feb. 2002 Page 64. Overhead/flipchart masterHydrology Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 75. HandoutHydrology Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 8 Add copy of the main text in chapter 7, for all participantsHydrology Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 96. Additional handoutThese handouts are distributed during delivery and contain test questions, answers toquestions, special worksheets, optional information, and other matters you would not like tobe seen in the regular is a good practice to pre-punch these additional handouts, so the participants can easilyinsert them in the main handout Project Training Module File: 12 How to analyse rainfall Version Feb.

8 2002 Page 107. Main textContents1 General12 Checking data homogeneity13 Computation of basic statistics24 Annual exceedance rainfall series45 Fitting of frequency distributions46 Frequency and duration curves97 Intensity-Frequency-Duration Analysis138 Depth-Area-Duration Analysis22 hydrology Project Training Module File: 12 How to analyse rainfall Version Feb. 2002 Page 1 How to analyse rainfall data1 General The purpose of hydrological data processing software is not primarilyhydrological analysis. However, various kinds of analysis are required for datavalidation and further analysis may be required for data presentation andreporting.

9 The types of processing considered in this module are: checking data homogeneity computation of basic statistics annual exceedance rainfall series fitting of frequency distributions frequency and duration curves Most of the hydrological analysis for purpose of validation will be carried out atthe Divisional and State data Processing Centres and for the final presentationand reporting at the State data Processing Checking data homogeneityFor statistical analysis rainfall data from a single series should ideally possessproperty of homogeneity - properties or characteristics of different portion of thedata series do

10 Not vary data for multiple series at neighbouring stations should ideally possess of homogeneity is required for validation purposes and there is a shared needfor such tests with other climatic variables. Tests are therefore described in otherModules as follows:Module 9 Secondary validation of rainfall homogeneity tests using double mass curvesModule 10 Correcting and completing rainfall rainfall data for long-term systematic shifts - doublemass curvesModule 17 Secondary validation of climatic series tests of homogeneity, including trend analysis,mass curves, residual mass curves, Student s t and Wilcoxon W-test on the difference of means and Wilcoxon-Mann-Whitney U-test to investigate if the sample are from same Multiple station validation including comparison plots, residualseries, regression analysis and double mass Project Training Module File.