Rajasthan PSC — Assistant Agriculture Engineer (Agriculture Engineering syllabus) · India · Rajasthan Public Service Commission
Original practice questions written to the published syllabus · not past papersRain to runoff: measuring precipitation, subtracting losses, estimating runoff and routing floods.
In the exams: GATE AG Section 4 Hydrology (SWCE is the heaviest GATE section, ~16 marks a year 2019–26); ICAR AIEEA-PG Unit VII; ICAR AICE subjects 40 and 43; NCEES PE hydrology; state PSCs
How our questions for Rajasthan PSC spread across the units of Watershed Hydrology. Difficulty: 19 easy, 14 medium, 4 hard.
| Drought classification | 6 | |
| Interception and evaporation (pan) | 5 | |
| Missing rainfall data and double-mass analysis | 4 | |
| Runoff estimation: rational method | 4 | |
| The hydrologic cycle | 3 | |
| Frequency analysis, return period and IDF curves | 3 | |
| Streamflow measurement | 3 | |
| Precipitation measurement and rain-gauge networks | 2 | |
| Runoff estimation: SCS curve number | 2 | |
| Hydrographs and the unit hydrograph | 2 | |
| Flood routing: Muskingum and reservoir (Puls) methods | 2 | |
| Infiltration: Horton, Philip and the phi-index | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which rain gauge produces a series of electrical pulses, each representing a fixed small depth of rain, and is therefore well suited to telemetry?
C. Tipping-bucket gauge
Each tip of the bucket closes a contact, so the count per unit time gives intensity. The natural-siphon gauge draws a mass curve on a chart, and non-recording and storage gauges give only totals.
Further reading: Subramanya, Engineering Hydrology
A double-mass curve shows a slope of 0.84 for the older part of a station's record and 1.05 for the recent part. The record is to be adjusted to current conditions. An old annual value of 72 cm becomes:
A. 90.0 cm
Pcx = Px × Mc/Ma = 72 × 1.05/0.84 = 90.0 cm, where Mc is the slope of the period adjusted to. 57.6 cm inverts the ratio; 75.6 cm multiplies by only one slope.
Further reading: Subramanya, Engineering Hydrology
Double-mass analysis of rainfall records is used to:
C. check and correct the consistency of a station's record
A break in slope of the double-mass curve shows a change in gauge site, exposure or practice. Missing data are filled by the normal ratio or averaging methods, not by double-mass analysis.
Further reading: Subramanya, Engineering Hydrology
The probability that a 50-year flood is equalled or exceeded in any one year is:
B. 0.02
p = 1/T = 1/50 = 0.02. 0.98 is the probability of non-exceedance; a 50-year event is not guaranteed once in 50 years. 0.64 is the chance of at least one exceedance in 50 years (1 − 0.98⁵⁰), and 0.36 is the chance of none (0.98⁵⁰).
Further reading: Subramanya, Engineering Hydrology
A 25 ha catchment has a runoff coefficient of 0.4 and a design intensity of 60 mm/h. The peak runoff by the rational method is:
B. 1.667 m³/s
With A in hectares, Q = CiA/360 = 0.4 × 60 × 25/360 = 1.667 m³/s. Using the km² constant 3.6 with hectares gives 166.7 m³/s (100 times too large), dividing by 36,000 gives 0.0167 m³/s, and omitting the constant gives CiA = 600.
Further reading: Subramanya, Engineering Hydrology
A grassed waterway drains 30 ha. The longest flow path is 700 m at a slope of 0.02, C = 0.45, and the local IDF relation is i = 1000 T^0.2/(D + 20)^0.8 (i in mm/h, D in min). For a 10-year return period, the design peak using Kirpich's tc is about:
D. 3.57 m³/s
tc = 0.01947 × 700^0.77 × 0.02^−0.385 = 13.6 min. i = 1000 × 10^0.2/(13.6 + 20)^0.8 = 95.2 mm/h. Q = 0.45 × 95.2 × 30/360 = 3.57 m³/s. Using a 60-minute duration instead of tc gives 1.78; entering tc in hours in the IDF formula gives 5.36 m³/s; the 3.6 constant with hectares gives 357 m³/s, 100 times too large.
Further reading: Subramanya, Engineering Hydrology
Hydrologic soil group A in the SCS curve number method refers to soils with:
D. high infiltration rates and low runoff potential, such as deep sands
Group A has the lowest runoff potential. Clays, high water tables and shallow soils over rock are group D.
Further reading: USDA NRCS National Engineering Handbook Part 630
A 60 ha catchment yields 35 mm of direct runoff in a storm. The runoff volume available for a farm pond is:
D. 21,000 m³
1 mm over 1 ha = 10 m³, so 35 × 10 × 60 = 21,000 m³. 2,100 and 210,000 m³ are factor-of-ten slips in the unit conversion, and 350 m³ forgets the area.
Further reading: Subramanya, Engineering Hydrology
A D-hour unit hydrograph is the direct runoff hydrograph resulting from:
B. one unit of effective rainfall spread uniformly over the catchment at a steady rate for D hours
The unit refers to effective (excess) rainfall, not total rainfall, and the duration D must be stated.
Further reading: Subramanya, Engineering Hydrology
For a district and week, current NDVI is 0.42, and the historical minimum and maximum NDVI for that week are 0.30 and 0.70. The Vegetation Condition Index is:
D. 30%
VCI = (NDVI − NDVImin)/(NDVImax − NDVImin) × 100 = (0.42 − 0.30)/(0.40) × 100 = 30%. 60% divides by the maximum only; 70% measures distance from the maximum instead. 42% simply reads the current NDVI as a percentage.
Further reading: WMO Handbook of Drought Indicators and Indices
Ten here, 37 in the app. The Laisha app has every practice question we have written to Rajasthan PSC in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
An AI operating system for agriculture: free guides, manuals and tools written for every country.