Test 5 - Infiltration and Phi-Index

Question 1 ప్రశ్న 1

Which statement best defines infiltration in hydrology?

A The process by which water at the ground surface enters the soil B The lateral movement of groundwater through a confined aquifer only C The evaporation of soil moisture into the atmosphere D The conversion of streamflow into rainfall

Question 2 ప్రశ్న 2

What is meant by infiltration capacity of a soil at a particular time?

A The maximum rate at which the soil can absorb water through its surface under the prevailing conditions when water is available for infiltration B The total porosity of the soil expressed in millimetres per hour C The rainfall intensity that must always occur during a storm D The volume of groundwater already stored below the water table

Question 3 ప్రశ్న 3

Rain reaches a soil surface at 6 mm/h while the current infiltration capacity is 15 mm/h. Neglecting interception and assuming the rainfall reaches the soil uniformly, what is the actual infiltration rate before any other supply becomes available?

A 6 mm/h B 9 mm/h C 15 mm/h D 21 mm/h

Question 4 ప్రశ్న 4

For an initially dry soil subjected to prolonged rainfall or ponding that continually supplies water at the surface, what is the usual qualitative behaviour of infiltration capacity?

A It is initially relatively high, decreases with time and approaches a lower near-steady value B It starts at zero and increases indefinitely C It remains exactly constant from the first instant D It becomes negative after the soil becomes wet

Question 5 ప్రశ్న 5

Which change would generally tend to reduce infiltration capacity, all other conditions being comparable?

A Compaction and surface sealing of the soil B Development of root channels and macropores C Improvement of soil aggregation and structure D Maintaining an open permeable surface instead of pavement

Question 6 ప్రశ్న 6

Which statement concerning vegetation and infiltration is generally most appropriate?

A Vegetation can promote infiltration by protecting the soil surface and creating root channels and organic-rich structure B Vegetation necessarily makes infiltration zero C Vegetation always converts infiltrated water immediately into surface runoff D Vegetation has no possible influence on soil surface condition

Question 7 ప్రశ్న 7

Horton's infiltration-capacity model is f(t) = fc + (f0 - fc)e^(-kt). If f0 = 70 mm/h, fc = 10 mm/h and k = 0.6 h^-1, what is f after 2 hours of continuous surface water supply?

A 18.1 mm/h B 28.1 mm/h C 40.0 mm/h D 58.1 mm/h

Question 8 ప్రశ్న 8

Under the infiltration-excess concept, what occurs when rainfall intensity exceeds the current infiltration capacity of the soil for a sufficient period?

A Water supplied in excess of infiltration capacity can become surface storage and rainfall excess that contributes to overland runoff B All rainfall must continue infiltrating regardless of soil capacity C The infiltration capacity immediately becomes equal to rainfall intensity by definition D Groundwater discharge must instantly stop

Question 9 ప్రశ్న 9

Which statement most accurately defines the phi-index for a storm?

A A constant loss rate selected so that the total rainfall depth above that rate equals the direct-runoff depth from the storm B The maximum instantaneous infiltration capacity measured at the start of rainfall C The final saturated hydraulic conductivity of every soil in the basin D The rainfall intensity at the time of peak stream discharge

Question 10 ప్రశ్న 10

Which statement about the physical interpretation of the phi-index is correct?

A It is a convenient constant abstraction rate for storm analysis and need not equal the true instantaneous infiltration capacity throughout the storm B It is exactly equal to the physical infiltration capacity at every instant C It is always equal to saturated hydraulic conductivity for every watershed D It is independent of the storm rainfall pattern and runoff response

Question 11 ప్రశ్న 11

A storm has a uniform rainfall intensity of 20 mm/h for 4 hours and produces 40 mm of direct-runoff depth. Assuming a constant phi-index and that rainfall intensity exceeds the index throughout the storm, what is the phi-index?

A 5 mm/h B 10 mm/h C 15 mm/h D 20 mm/h

Question 12 ప్రశ్న 12

A storm hyetograph consists of three successive 1-hour rainfall intensities of 10, 30 and 20 mm/h. The measured direct-runoff depth is 25 mm. What is the phi-index?

A 10.0 mm/h B 12.5 mm/h C 15.0 mm/h D 17.5 mm/h

Question 13 ప్రశ్న 13

A storm has four successive 1-hour rainfall intensities of 5, 15, 25 and 10 mm/h. If the direct-runoff depth is 20 mm, what is the phi-index?

A 5 mm/h B 10 mm/h C 12.5 mm/h D 15 mm/h

Question 14 ప్రశ్న 14

A storm has rainfall intensities of 12, 28 and 16 mm/h during three successive 30-minute intervals. If direct-runoff depth is 8 mm, what is the phi-index?

A 10 mm/h B 12 mm/h C 14 mm/h D 16 mm/h

Question 15 ప్రశ్న 15

A storm has four successive 30-minute rainfall intensities of 8, 20, 30 and 12 mm/h. If the phi-index is 15 mm/h, what total rainfall-excess depth is produced?

A 5 mm B 10 mm C 15 mm D 20 mm

Question 16 ప్రశ్న 16

A uniform storm produces 60 mm of rainfall in 3 hours. If the phi-index is 8 mm/h and rainfall intensity exceeds the index throughout the storm, what direct-runoff depth is represented by the phi-index model?

A 24 mm B 30 mm C 36 mm D 52 mm

Question 17 ప్రశ్న 17

A 5 km² catchment experiences three successive 1-hour rainfall intensities of 10, 25 and 15 mm/h. The storm produces 50,000 m³ of direct runoff. Assuming a spatially uniform storm and a constant phi-index, what is the phi-index?

A 10 mm/h B 12.5 mm/h C 15 mm/h D 20 mm/h

Question 18 ప్రశ్న 18

When applying a phi-index to a hyetograph, how should a time interval with rainfall intensity lower than the phi-index be treated?

A Its rainfall contributes no rainfall excess, and the actual abstraction during that interval cannot exceed the rainfall supplied B The phi-index must be subtracted from the rainfall even if this gives negative effective rainfall C The interval must always contribute direct runoff equal to the phi-index D The rainfall intensity must be replaced by zero before calculating infiltration

Question 19 ప్రశ్న 19

When a phi-index is determined from an observed storm hydrograph, which runoff quantity should normally be matched to the computed rainfall-excess depth?

A Direct-runoff depth obtained after separating baseflow from the storm hydrograph B Total streamflow volume including long-term baseflow from previous groundwater storage C Only the peak discharge value expressed in cubic metres per second D Annual groundwater recharge

Question 20 ప్రశ్న 20

Which statement best distinguishes the W-index from the phi-index in traditional engineering hydrology?

A The W-index represents an average infiltration rate after explicitly excluding specified initial abstractions such as interception and depression storage, whereas the phi-index can absorb such losses into its constant storm-loss rate B The W-index is always the maximum instantaneous infiltration capacity C The phi-index excludes all initial abstractions while the W-index necessarily includes them D The W-index is a rainfall-intensity measurement made by a recording gauge

Question 21 ప్రశ్న 21

A uniform 5-hour storm produces 100 mm of rainfall and 40 mm of direct runoff. Rainfall intensity exceeds both infiltration indices throughout the storm. If initial abstraction is 10 mm, what are the phi-index and W-index respectively using the traditional simplified definitions?

A 10 mm/h and 12 mm/h B 12 mm/h and 10 mm/h C 8 mm/h and 10 mm/h D 12 mm/h and 12 mm/h

Question 22 ప్రశ్న 22

For the same rainfall hyetograph, if the adopted phi-index is reduced while all rainfall intensities remain unchanged, what is the general effect on computed rainfall-excess depth?

A It increases or remains unchanged because a larger portion of rainfall lies above the lower loss threshold B It must decrease C It is completely independent of the phi-index D It becomes negative

Question 23 ప్రశ్న 23

Which statement most accurately describes the relationship between the final near-steady infiltration capacity of a soil and its earlier infiltration behaviour during a long storm?

A The initial infiltration capacity can be substantially higher, while the capacity commonly declines toward a lower near-steady value as the soil wets B The initial and final capacities must always be identical C The final capacity must always be greater than the initial capacity D The infiltration capacity becomes exactly equal to rainfall intensity regardless of soil properties

Question 24 ప్రశ్న 24

Two otherwise comparable catchments receive the same intense storm. Catchment X has compacted, crusted soil, while Catchment Y has well-structured vegetated soil with effective macropores. Which response is generally more likely?

A Catchment X has lower infiltration opportunity and greater potential for infiltration-excess runoff B Catchment X necessarily infiltrates all rainfall while Catchment Y produces all runoff C Both catchments must have identical infiltration capacity because rainfall is identical D Vegetation makes infiltration impossible in Catchment Y

Question 25 ప్రశ్న 25

Which sequence most appropriately represents the development of infiltration-excess runoff during an intense storm on initially unsaturated soil?

A Rainfall begins → water infiltrates while supply is within soil capacity → rainfall intensity eventually exceeds the declining infiltration capacity → surface excess develops and can contribute to runoff B Rainfall begins → all infiltration immediately stops → groundwater rises before any soil wetting → runoff becomes negative C Rainfall begins → infiltration capacity becomes infinite → no surface water can ever form D Rainfall begins → direct runoff occurs only after all groundwater has evaporated

Question 26 ప్రశ్న 26

Consider the following statements about infiltration and infiltration indices: I. Actual infiltration cannot exceed the water supply reaching the soil surface. II. Infiltration capacity commonly decreases from a high initial value toward a lower near-steady value during prolonged wetting. III. The phi-index is selected so that rainfall excess above the constant index equals direct-runoff depth. IV. The W-index can account separately for specified initial abstractions. Which option is correct?

A I and II only B I, II and III only C II, III and IV only D I, II, III and IV

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