Assignment No. 1Analysis of rainfall data (Double mass curve technique/Missing rainfall data).

1. Explain how you will calculate missing rainfall data at station. 2. What are the WHO recommendations for density of rain gauge network? Based on this

what are the recommendations by Indian Standard (IS: 8389-1983)?3. Explain with procedure and example the double mass curve technique.4. The annual rainfall data, being reported from a station A, for 22 years are available, since 1969.

In order to check the consistency of this data, six neighboring stations have been chosen and the annual rainfall values of these stations have been averaged for all the years on record since 1969. These values are given below

Year Yearly precipitation at station A in cm

6 station average yearly precipitation in cm

1969 177 1431970 144 1321971 178 1461972 162 1471973 194 1611974 168 1551975 196 1521976 144 1171977 160 1281978 196 1931979 141 1561980 158 1641981 145 1551982 132 1431983 95 1151984 148 1351985 142 1631986 140 1351987 130 1431988 137 1301989 130 1461990 163 161

(a) Find out if any inconsistency in precipitation record of station A is indicated? And if yes, since when a change in precipitation regime id indicated?

(b) Adjust the recorded data at station A and determine its mean annual precipitation.

5. Precipitation station X was inoperative for part of a month during which a storm occurred. The respective storms totals at three surrounding stations A, B and C were 107, 89 and 122 mm. The normal annual precipitation amounts of stations A, B and C are respectively 978, 1120, 935 and 1200 mm. Estimate the storm precipitation for station X.

6. The rain gauge station X did not function for a part of month during which a storm occurred. The storm produced rainfalls of 84, 70 and 96 mm at three surrounding stations

A, b and C respectively. The normal annual rainfalls at the stations X, A, B and C respectively 770, 882, 736 and 944 mm. Estimate the missing storm at station X.

7. The normal annual precipitation of five rain gauge stations P, Q, R, S and T are respectively 125, 102, 76, 113 and 137 cm. During a particular storm the precipitation recorded by stations P, Q, R and S are 13.2, 9.2, 6.8 and 10.2 respectively. The instrument at station T was inoperative during the storm. Estimate the rainfall at station T during that storm by normal ratio method.

Assignment No. 2Marking catchment area on a topo-sheet and working out average annual precipitation

anddetermining yield by various methods

.1. Define precipitation. State any six forms of precipitation2. State different types of precipitation. Explain cyclonic & orographic precipitation3. Explain different types of rain gauges with neat sketches4. Describe principle of rainfall measurement using RADAR with neat sketch, also state its

advantages over other rain gauges.5. The isohyetal map for 24 hours storm gave the area enclosed between different isohyets as

follows.Isohyets in mm

21 20 19 18 17 16 15 14 13 12

Enclosed area in sq.km.

543 1345 2030 2545 2955 3280 3535 3710 3880 3915

Determine the average depth of rainfall over the basin6. The area as shown in figure is composed of a square plus an equilateral triangle plot of

side 10 km. the annual precipitation at the rain gauge stations located at the four corners and center of the square plot and apex of the triangular plot are indicated in figure. Find the mean precipitation over the area by Thiessen polygon method and compare with the arithmetic mean. (46 cm) A B (65 cm)

(60 cm) F

E (70cm)

D (80 cm) C (76 cm)

7. Toposheet is giving data regarding point rainfall at different stations. Compare the average rainfall over catcment area by different methods

Station No. Rainfall in mm1 529.52 556.03 578.54 545.95 529.8