Bissoy.com
Doctors Medicines MCQs Q&A

An 8-hour storm with incremental rainfall during each successive hour is tabulated herewith. What will be the correction to total runoff when, whereas the actual ϕ index was 0.5 cm/hour, a wrong magnitude of 0.6 cm/hour was adopted in computing the total runoff? Time from start (hour) Incremental rainfall in each hour (cm) 1 0.4 2 0.8 3 1.2 4 0.9 5 1.8 6 1.0 7 0.3 8 0.8

An 8-hour storm with incremental rainfall during each successive hour is tabulated herewith. What will be the correction to total runoff when, whereas the actual ϕ index was 0.5 cm/hour, a wrong magnitude of 0.6 cm/hour was adopted in computing the total runoff? Time from start (hour) Incremental rainfall in each hour (cm) 1 0.4 2 0.8 3 1.2 4 0.9 5 1.8 6 1.0 7 0.3 8 0.8 Correct Answer + 0.6 cm

Concept:

ϕ index: This is defined as the rate of infiltration above which the rainfall volume equals runoff volume, as shown in Figure

Φ index= (Total rainfall volume equals runoff volume-Runoff)/Effective time of rainfall

W-index: This is the average infiltration rate during the time when the rainfall intensity exceeds the infiltration rate.

Thus, W may be mathematically calculated by dividing the total infiltration (expressed as a depth of water) divided by the time during which the rainfall intensity exceeds the infiltration rate.

Total infiltration = Total precipitation – Surface runoff – Effective storm retention

Calculation:

Actual ϕ index = 0.5 cm/hour,

Wrong magnitude of ϕ index = 0.6 cm/hour

So, wrong runoff  = Total rainfall - (ϕ index*te)

ϕ = (0.8 + 1.2 + 0.9 +1 .8 + 1 + 0.8) - (0.6*6) = 2.9 cm

Correct runoff = (0.8 + 1.2 + 0.9 + 1.8 + 1 + 0.8) - (0.5*6) = 3.5 cm

∴ Correction = 3.5 - 2.9 = 0.6 cm

Related Questions

A 6 hours storm had 4 cm of rainfall and the resulting runoff was 2 cm. If ϕ index remains at the same value, the runoff due to 10 cm of rainfall in 12 hours in the catchment is
Which of the following will pose difficulties in adopting U.H.G. principles and processes in evaluating flood hydrographs of basins? 1. non-uniform real distribution within a storm 2. Intensity variation within a storm 3. The centre of the storm varies from storm to storm in case of large catchments 4. Dividing into a number of sub-basins and routing the individual DRHs through their respective channels to obtain the composite DRH at the basin outlet 5. Large storages within the catchment
Consider the following statements: 1. The normal annual rainfall of a station is obtained as the arithmetic average of the successive annual rainfall in the last 30 years. 2. The “normal rainfalls” are updated by deleting the needful number of oldest years’ data from the record and adding the needful number of most recent years’ data to the record. 3. The standard deviation computed for the rainfall data is taken as a measure of the variability of the rainfall during the self-same set of years. 4. If the observed rainfall in any year is less than the current average annual rainfall, then that year is called a dry year. Which of the above statements are correct?
The rainfall in Shillong for the first two days was in the ratio of 6 : 7. The average rainfall for the last four days was recorded to be 0.90 inch. The average rainfall of six days was 1.25 inch. Which of the following is/are correct? A. Average rainfall on 2nd day is 2.8 inch B. Average rainfall on 1st day is 1.8 inch C. Average rainfall on 2nd day is 2.1 inch D. Average rainfall on 1st day is 2.4 inch
A pipe, working at full speed, can fill an empty cistern in 1 hour. However, during the first hour it worked at one-twenty-fourth of its capacity, during the second hour at one-twelfth of its capacity, during the third hour at one-eighth of its usual capacity, during the fourth hours at one-fourth of its usual capacity and during the fifth hour it was only one-half as efficient as it was supposed to be. A second pipe also displayed similar performance, but if it worked at full speed would have filled the empty cistern in 2 hours. Together with a drain pipe that drained water out of the tank a constant rate, the empty cistern could be filled in 5 hours, all the three pipe working concurrently. How many hours will it take the drain pipe to empty the filled cistern if no other pipe was functioning during the time?
In order to determine acidic, basic or neutral character of solutions, a student tabulated the following results after experimentation. Which of the following observations has been tabulated correctly? Case Test Solution Colour change on red litmus paper Colour change on blue litmus paper Acidic/Basic/Neutral A NaOH No change Red Acidic B Sour Milk Blue No change Neutral C Vinegar No change No change Neutral D Washing soda Blue No change Basic
In order to determine acidic, basic or neutral character of solutions, a student tabulated the following results after experimentation. Which of the following observations has been tabulated correctly? Case Test Solution Colour change on red litmus paper Colour change on blue litmus paper Acidic/Basic/Neutral A NaCl No change Red Acidic B Lime water Blue No change Neutral C Vinegar No change No change Neutral D Washing soda Blue No change Basic
The monthly rainfall chart based on 50 years of rainfall in Agra is shown in the following figure. Which of the following are true? (k percentile is the value such that k percent of the data fall below that value) (i) On average, it rains more in July than in December (ii) Every year, the amount of rainfall in August is more than that in January (iii) July rainfall can be estimated with better confidence than February rainfall (iv) In August, there is at least 500 mm of rainfall
In the following question, sentences of a paragraph have been jumbled and labelled as A, B, C and D. You are required to rearrange the jumbled sentences of the paragraph and mark your response accordingly by selecting the correct option. A: Water harvesting means capturing rain where it falls or capturing the runoff in your own village or town. B: It also provides for the measures that should be taken to keep that water clean by not allowing polluting activities to take place in the catchment. C: Water harvesting can be undertaken through a variety of ways, such as, capturing runoff from rooftops, capturing runoff from local catchments, capturing seasonal floodwaters from local streams, etc. D: These techniques can serve purposes, such as, provide drinking water, provide irrigation water, increase groundwater recharge, etc.
A pipe, working at full speed, can fill an empty cistern in 1 hour. However, during the first hour it worked at one-twelfth of its capacity, during the second hour at one-ninth of its capacity, during the third hour at one-sixth of its usual capacity and during the fifth hour it was only one -third as efficient as it was supposed to be. A second pipe also displayed similar performance, but if it worked at full speed would have filled the empty cistern in 2 hours. Together with a drain pipe that drained water out of the tank at a constant rate, the empty cistern could be filled in 5 hours, all the three pipes working concurrently. How many hours will it take the drain pipe to empty the filled cistern if no other pipe was functioning during the time?