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Discuss rainfall deficiency commonly occurring in most countries under the following: a)The index of wetness. b)Normal rainfall. c)Consistency of recording. d)Rainfall frequency analysis.

      

Discuss rainfall deficiency commonly occurring in most countries under the following:
a)The index of wetness.
b)Normal rainfall.
c)Consistency of recording.
d)Rainfall frequency analysis.

  

Answers


Jim
a)The index of wetness is the ratio of actual rainfall in a particular year at a place to the corresponding normal rainfall.In a particular year, the rainfall may not be equal to the mean annual rainfall.
b)Normal rainfall is the annual rainfall averaged from the record of 35 years.
-An area with normal rainfall less than 40 cm is called arid, 40-75 cm semi-arid and above 75 cm as humid.
c)Consistency of recording.
-Is commonly tested by comparing its accumulated annual or seasonal rainfall with the concurrent values of mean rainfall of a group of adjoining stations termed as base stations.
-The inconsistency of the record of a station arises due to:
i)Change in location of rain-gauge.
ii)Change in exposure.
iii)Changes in instrument or observational procedure.
d)Rainfall frequency analysis.
-Is defined as the rainfall which can be expected to be equaled or exceeded on the average once every year rainfall.
-Exceedence interval is the average number of years between the occurrence of an event and a greater event.
-The recurrence interval is the average number of years within which a given rainfall event will be equaled or exceeded.
-Frequency of occurrence of maximum and minimum rainfall is determined to predict the future rainfall trends for the design of river protection works, drainage works, etc.
-Various methods of determining recurrence interval are:
a)California method.
b)Hazen’s method.
c)Weibull method.
d)Gumbel’s method.
jim items answered the question on March 5, 2019 at 17:12


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