1. WFM 6202: Remote Sensing and GIS in Water Management
[Part-B: Geographic Information System (GIS)]
Case study: Generation of rainfall contour map using spatial analysis of GIS
Akm Saiful Islam
Institute of Water and Flood Management (IWFM)
Bangladesh University of Engineering and Technology (BUET)
February, 2008

2. Problem statement
“This case study will show how to generate a rainfall contour map of over Bangladesh based on the data collected in different rain gauge stations.”
Given data:
A shape file which contains different Thana boundary of Bangladesh
A text file contains locations of rain gauge stations and mean daily rainfall values (mm/day) of that station

3. Outline of the Exercise
Create a Shape file of rain gauges from station data in a ASCII text file
Creating District map of Bangladesh using generalization technique from Thana map of Bangladesh.
Create rainfall contour map of rainfall of Bangladesh by surface interpolation

4. Add Thana Shape file of Bangladesh

5. Create District Maps from Thana Maps
Click on Dissolve tools
Select District name field

6. District Maps of Bangladesh with unique color

7. Change Layer Property Double click on the Layer
Select Categories from Symbology tab
District name as Value Field
Click on Add All values
You can also change color scheme

8. District Map of Bangladesh
Rename the layer as District

9. Add Rainfall Text files as table
Click on Add Data and select rainfall.txt
Open it as table

10. Table of Rainfall Data

11. Create Shape file from Rainfall table
Click on Make XY Event Layer
Select rainfall table
Longitude as X Field and Latitude as Y field

12. Rain gauge stations as shape file

13. Rain gauge stations
Label features

14. Turn on Spatial Analyst Extension
First load the Spatial Analyst
click on Tools > Extension
Check the box left to Spatial Analyst

15. Masks Interpolation region
Click options from Spatial Analyst
Select District as analysis mask

16. Step-7: Create contour of rainfall by surface interpolation
Click Surface > Interpolate Grid
Select Output grid extent as Disolv1.shp
Select MeanDailyRain as Z Value Field

17. Interpolation using IDW method
Click on IDW method of interpolation
Select Z value field as MeanDailyRain

18. Rainfall map of Bangladesh

19. Find Mean Rainfall for each district
Click Zonal Statistics

20. Zonal statistics for each distric

21. Rainfall in each district of Bangladesh
Change symbology of district maps to zstat.MEAN
Turn on Label