ONR 002 Solved Guess Paper for the 2026 sessions is a 16 page answer file covering 15 expected questions of Basics of Hydrology, the course IGNOU codes as ONR-002 under the Certificate in Water Harvesting and Management. Every answer opens with the definition used in the IGNOU block and closes with an evaluative line the examiner can tick.
Five complete answers are reproduced on this page so you can judge the writing quality before you ask for the remaining 10.
ONR 002 Guess Paper Key Facts
| Course code and title | ONR-002 Basics of Hydrology |
|---|---|
| Parent programme | Certificate in Water Harvesting and Management (CWHM) |
| Questions in the file | 15 expected questions with full model answers |
| Shown on this page | 5 complete answers as samples |
| Available on request | Remaining 10 answers |
| Length | 16 pages |
| Syllabus coverage | 3 blocks and 7 units |
| Papers analysed | 6 sessions from June 2023 to December 2025 |
| Exam duration and marks | 2 hours and 50 marks |
| Paper structure | 8 questions set and any 5 to be attempted |
| Target sessions | June 2026 and December 2026 term end examinations |
ONR 002 Solved Guess Paper 2026 and What the File Contains
The file carries 15 questions written in IGNOU examination phrasing, each followed by a complete answer sized to its marks, and it targets both the June 2026 and December 2026 term end examinations.
Basics of Hydrology is a theory paper where marks are lost less to difficulty and more to shape. Students know what infiltration is, then write 400 rambling words when the examiner wanted a definition, a measurement method and five factors. Each answer here is built to that shape instead, with the definition first and the numbered list the block itself uses.
Every answer states the marks and a word target above it, so a 10 mark question runs to roughly 250 words and a 5 mark part to roughly 150. Writing to length matters in a two hour paper where five answers have to be finished. Students who use our IGNOU Solved Guess Paper library tell us the word discipline is what actually saves them time in the hall.
The figures the examiner looks for are kept intact rather than rounded away. The 0.25 mm tip of a tipping bucket gauge, the 0.70 pan coefficient of the US Class A pan, the 1300 hectare ceiling on the rational formula and the 30 cm and 60 cm infiltrometer rings all appear exactly as the block states them.
Sample Questions with Answers from the ONR 002 Basics of Hydrology Guess Paper
Five of the 15 answers are reproduced below in full, exactly as they appear in the file, and four of these five topics were set in the December 2025 ONR 002 paper.
These are not trimmed extracts. What you read here is the complete answer a student would write in the examination, including the opening definition, the numbered body and the closing conclusion line.
Explain the hydrologic cycle with the help of a neat sketch and describe its components.
Meaning of Hydrologic Cycle
The unending process of circulation and redistribution of water by the atmosphere and the earth is called the hydrologic cycle.
Nature of the Cycle
It is a continuous process with neither beginning nor end, circulating water from the sea, through the atmosphere, to the land, and back again to the sea. Evaporation and precipitation are its driving forces, with solar radiation as the source of energy and gravity keeping water in motion.
Six Major Components
- Evapotranspiration: water vaporises from oceans, soil and plant surfaces into the atmosphere.
- Condensation: rising water vapour cools and condenses over nuclei to form clouds.
- Precipitation: condensed moisture falls back to earth as rain or snow.
- Infiltration: a part of precipitation enters the soil surface.
- Percolation: infiltrated water moves downward to recharge the groundwater.
- Runoff: the remaining rainfall flows overland into streams and rivers, finally reaching the oceans from where it evaporates again.
Conclusion: The cycle continually balances the waters of the earth and the moisture in the atmosphere; oceans hold 96.5% of water while only 2.5% is fresh, making the cycle vital for the fresh-water supply.
Define infiltration. Write the factors affecting it. How is it measured? Explain.
Meaning of Infiltration
The process of water entering the soil surface is known as infiltration; it is the downward entry of water into the immediate surface of soil.
Key Terms
The rate at which water enters the soil is the infiltration rate (cm/hr); it starts as the initial rate and settles to a steady basic infiltration rate. The maximum rate possible under given conditions is the infiltration capacity, and the total depth infiltrated in a given time is the accumulated infiltration.
Measurement of Infiltration
Infiltration is measured using a single or double ring infiltrometer. The inner and outer rings have diameters of 30 cm and 60 cm with 25 cm height, driven about 10 cm into the soil. Water fills both rings; a constant depth is kept in the outer ring to minimise lateral flow, while the fall of water in the inner ring is read at intervals until the rate becomes constant, giving the basic infiltration rate.
Factors Affecting Infiltration
- Type of soil surface: vegetative surfaces infiltrate far more than bare or clogged surfaces.
- Initial soil moisture: dry surfaces infiltrate faster than moist ones.
- Temperature: an increase in soil temperature enhances the rate.
- Soil texture: sandy (light) soils infiltrate faster than clay (heavy) soils.
- Soil compaction: compacted soils give a lower rate than loose soils.
Conclusion: Infiltration governs soil-moisture storage and groundwater recharge; the basic infiltration rate is the value of significance in watershed and hydrological studies.
(a) Explain the functioning of the Tipping-Bucket type rain gauge. (b) Enlist the different types of recording rain gauges and write their advantages.
(a) Tipping Bucket Type Rain Gauge
The tipping bucket rain gauge comprises a pair of buckets pivoted under a funnel so that when one bucket receives 0.25 mm of rainfall it tips, discharging its contents and bringing the other bucket under the funnel.
Each tip is recorded by an electrically driven pen on a clockwork-driven chart, marking the time of every tip; water from the tipped bucket is collected in a storage can and measured at intervals as a check. The gauge is ideally suited to measuring rainfall intensity for short periods and to digitizing the output signal.
(b) Types of Recording Rain Gauges and Advantages
- Float (natural-syphon) type: rain raises a float whose pen traces rainfall on a clock-driven drum.
- Weighing bucket type: a bucket on a spring or lever balance records its increasing weight on a chart.
- Tipping bucket type: tips at every 0.25 mm and records rainfall intensity.
Advantages
- They provide a continuous record of rainfall over time.
- They yield the duration, intensity and cumulative rainfall of a storm.
- The cumulative mass curve lets intensity be read directly from its slope.
Conclusion: Installed alongside non-recording gauges for calibration, recording gauges supply the detailed time-distribution of rainfall essential for design of water-harvesting structures.
(a) Explain the Thiessen polygon method of average rainfall estimation and write its limitations. (b) Describe the Isohyetal method of estimation of average rainfall.
(a) Thiessen Polygon Method
In the Thiessen polygon method, the rainfall recorded at each station is given weightage on the basis of an area closest to the station.
- All gauges in and around the catchment are accurately marked on a scaled map.
- Consecutive stations are joined to form a network of triangles.
- Perpendicular bisectors of the triangle sides form polygons; mean rainfall = Σ(A×R) ÷ ΣA.
Limitations
- New polygons must be redrawn whenever a gauge is added or removed; orographic features, linear-variation assumption and topographic barriers are not accounted for.
(b) Isohyetal Method
Lines connecting points of equal rainfall (isohyets) are drawn over the catchment; this method gives better results than the arithmetic-mean and Thiessen methods.
- Gauges are marked on a scaled map and the rainfall depth at each is noted.
- Isohyets are drawn by interpolation; closely spaced isohyets indicate a higher rainfall gradient.
- Area between successive isohyets is measured by planimeter; average rainfall = Σ(mean of two isohyets × area) ÷ total area.
Conclusion: The Isohyetal method gives the most accurate result as it represents the actual rainfall pattern, while the Thiessen method suits uneven gauge distribution.
Define water pollution. Describe the sources of surface and groundwater pollution.
Meaning of Water Pollution
Water pollution may be defined as an undesirable change in the physical, chemical or biological characteristics of water that may have a harmful effect on human life and other living species.
Sources of Surface Water Pollution
- Sewage pollution: domestic and animal waste carrying disease-causing micro-organisms and oxygen-demanding matter.
- Industrial waste: toxic heavy metals and acids, alkalis and cyanides discharged by textile, sugar, paper and fertilizer industries.
- Agricultural waste: fertilizers, pesticides and farm waste leaching into open water bodies.
- Physical pollutants: radioactive, thermal and oil wastes that harm aquatic life; siltation is a natural source.
Sources of Groundwater Pollution
- Micro-organisms from human and animal waste and the leaching of waste dumps and sewage.
- Inorganic contaminants such as chloride, nitrate, fluoride, iron and sulphate.
- Organic compounds such as Aldrin, DDT and tetrachloride from excessive pesticide use.
- Agricultural practices that leach nitrate into the groundwater.
Conclusion: Surface and groundwater pollution are closely interlinked; identifying the source is the first step before remedial measures, and groundwater pollution is far harder to detect and treat.
Compare Sample 1, Sample 2, Sample 4 and Sample 5 against the December 2025 ONR 002 Question paper and you will find the same four topics set as Questions 1, 2, 5 and 7. That is the standard the remaining 10 answers are written to.
Complete Question Index of the ONR 002 Basics of Hydrology Guess Paper
All 15 questions are listed below with their block and unit mapping, so you can see exactly which part of the syllabus each answer belongs to before you ask for the file.
| No. | Question topic | Block and unit | Concepts the answer develops | Marks |
|---|---|---|---|---|
| Q1 | Hydrologic cycle and its components | Block 1 Unit 1 | Six components from evapotranspiration to runoff, 96.5% ocean and 2.5% fresh water split | 10 |
| Q2 | Water budget and balance equation | Block 1 Unit 2 | I minus O equals delta S, expanded catchment form, four characteristics of water balance | 10 |
| Q3 | Forms of precipitation and conditions | Block 1 Unit 1 | Rain, snow, drizzle, glaze, sleet and hail with size limits, four conditions for formation | 6 + 4 |
| Q4 | Rainfall intensity and IDF analysis | Block 1 Unit 1 | Light, moderate and heavy bands in mm per hour, seven uses of the IDF relationship | 5 + 5 |
| Q5 | Infiltration factors and measurement | Block 1 Unit 2 | Double ring infiltrometer dimensions, infiltration capacity versus basic rate, five factors | 10 |
| Q6 | Percolation and its affecting factors | Block 1 Unit 2 | Deep percolation, percolation rate and path, hydraulic conductivity and gradient | 5 + 5 |
| Q7 | Evaporation measurement and factors | Block 1 Unit 2 | US Class A pan dimensions and 0.70 pan coefficient, six influencing factors | 10 |
| Q8 | Runoff and factors affecting it | Block 1 Unit 1 | Five climatic and five physiographic factors, catchment shape and drainage density | 10 |
| Q9 | Types of rainfall and tropical cyclone | Block 2 Unit 3 | Convective, orographic, cyclonic and thunderstorm rainfall, cyclone origin at 5 to 10 degrees | 10 |
| Q10 | Rain gauges tipping bucket and recording | Block 2 Unit 3 | 0.25 mm tip mechanism, float and weighing bucket types, cumulative mass curve slope | 5 + 5 |
| Q11 | Thiessen and Isohyetal methods | Block 2 Unit 3 | Polygon weighting formula, isohyet interpolation and planimeter area measurement | 5 + 5 |
| Q12 | Rational method of peak runoff | Block 2 Unit 4 | Qp equals 0.0278 C I A, weighted runoff coefficient, time of concentration formula | 10 |
| Q13 | Sources of surface and groundwater pollution | Block 3 Unit 5 | Sewage, industrial, agricultural and physical sources, inorganic and organic contaminants | 10 |
| Q14 | Physical and chemical characteristics of water | Block 3 Unit 6 | Colour in Hazen units, turbidity, conductivity in dS per m, pH scale and hardness as CaCO3 | 5 + 5 |
| Q15 | Conventional and household water treatment | Block 3 Unit 7 | Aeration to filtration sequence, 85% settling, boiling, chlorination at 2 ppm and SODIS | 5 + 5 |
Questions Q1, Q5, Q10, Q11 and Q13 are the five reproduced above. The other 10 answers, covering the water budget, precipitation forms, IDF analysis, percolation, evaporation, runoff factors, rainfall types, the rational method, water quality parameters and treatment, are sent on request.
How This ONR 002 Solved Guess Paper Was Built from Past Papers
Six consecutive term end papers from June 2023 to December 2025 were tabulated topic by topic, and the 15 questions were selected from repeat topics and recent gaps rather than from the syllabus index.
The method is unglamorous. Each paper was opened, every question tagged to a block and unit, and the result entered in a grid of topics against sessions. Anything appearing four or more times, or absent for two sessions after a long run, was marked high priority. That grid is reproduced in the file so you can check the reasoning rather than take it on trust.
Sources were the papers IGNOU itself publishes. The December 2025 paper sits on the university site as the official ONR-002 question paper PDF, and the block content was checked against the eGyanKosh self learning material for all seven units.
If you want to run the same check yourself rather than take our grid on trust, our IGNOU Previous Year Question Paper collection has the earlier sessions gathered in one place.
Answers were then written by a subject faculty member against the block text, not paraphrased from general hydrology books. Where the block gives a number, the number is kept. Where the block gives a list of four, the answer gives four and does not invent a fifth to look thorough.
One honest limit is worth stating. A guess paper narrows preparation, it does not predict a paper. Four of our five sample topics appeared in December 2025, which is a good hit rate, but the December 2025 paper also carried a WMO rain gauge network question that sits outside the 15. Treat this as a priority order for revision, not as a substitute for reading the blocks.
Block and Unit Structure of ONR 002 Basics of Hydrology
ONR-002 is organised into 3 blocks and 7 units, and the 15 guess paper questions are distributed across all seven units with the heaviest weight on Block 1 and Block 2.
| Block | Unit | Unit title | Core ideas examined | Guess paper questions |
|---|---|---|---|---|
| Block 1 Elementary Hydrology | Unit 1 | Introduction to Hydrology | Hydrologic cycle, precipitation forms, rainfall intensity bands, runoff generation | Q1, Q3, Q4, Q8 |
| Unit 2 | Hydrological Losses | Water budget, infiltration, percolation, evaporation and interception losses | Q2, Q5, Q6, Q7 | |
| Block 2 Rainfall and Runoff Measurement | Unit 3 | Rainfall and its Measurements | Rainfall types, recording and non recording gauges, Thiessen and isohyetal averaging | Q9, Q10, Q11 |
| Unit 4 | Measurement and Estimation of Runoff | Rational formula, time of concentration, volumetric and velocity area methods | Q12 | |
| Block 3 Water Quality | Unit 5 | Water Pollution | Surface and groundwater pollution sources, industrial and agricultural contaminants | Q13 |
| Unit 6 | Water Quality Parameters | Colour, turbidity, conductivity, pH, hardness and permissible drinking water limits | Q14 | |
| Unit 7 | Water Quality Basic Treatment Measures | Conventional treatment sequence, slow sand filtration, household disinfection methods | Q15 |
Block 1 alone accounts for eight of the fifteen questions, which mirrors how the papers behave. Hydrologic cycle, infiltration, percolation and evaporation questions have carried the opening marks in nearly every recent session.
ONR 002 Exam Pattern and Marking Scheme for the Term End Examination
The ONR 002 term end paper runs for 2 hours, carries 50 maximum marks, sets 8 questions of equal weight and asks you to attempt any 5, which works out to 10 marks per question.
Question splits vary. Some questions are single 10 mark items, others break into 5 plus 5 or 6 plus 4. The last question is usually a short notes or differentiate between item worth 2 into 5. December 2025 followed exactly this shape, with a differentiate question at number 4 and a write notes on any two at number 8.
Numerical work appears in most sessions, typically a rainfall intensity computation from cumulative rainfall data or a Thiessen polygon average. Calculator use has been permitted in several sessions. Practise the method rather than memorising worked sums, because the data changes every time while the procedure does not.
Word targets follow the marks. Roughly 250 words for a 10 mark question, roughly 150 for a 5 or 6 mark part. Writing longer does not add marks and costs you a question at the end. The examination is set bilingually in English and Hindi, and answers in this file are written in English.
Topic Frequency Across Six ONR 002 Question Papers
The table below maps 14 recurring topics against the six sessions from June 2023 to December 2025, and the priority band in the final column is what decided which questions entered the file.
| Topic | Jun 2023 | Dec 2023 | Jun 2024 | Dec 2024 | Jun 2025 | Dec 2025 | Priority |
|---|---|---|---|---|---|---|---|
| Hydrologic cycle, water budget and balance | Yes | Yes | Yes | No | Yes | Yes | High |
| Rainfall intensity and IDF relationship | No | Yes | No | Yes | Yes | Yes | High |
| Infiltration factors and measurement | No | Yes | No | No | Yes | Yes | High |
| Percolation and deep percolation | No | No | Yes | Yes | Yes | No | High |
| Evaporation and evapotranspiration | No | Yes | No | Yes | Yes | Yes | High |
| Runoff and factors affecting it | Yes | No | Yes | Yes | Yes | No | High |
| Rain gauges, tipping bucket and recording | Yes | No | Yes | Yes | Yes | Yes | High |
| Average rainfall by Thiessen and isohyetal | Yes | Yes | No | Yes | Yes | Yes | High |
| Sources of surface and groundwater pollution | Yes | No | Yes | Yes | No | Yes | High |
| Physical and chemical characteristics of water | Yes | No | Yes | Yes | Yes | No | High |
| Conventional water treatment | Yes | Yes | Yes | No | Yes | Yes | High |
| Types of rainfall and tropical cyclone | Yes | Yes | Yes | Yes | No | No | Medium |
| Forms of precipitation and conditions | Yes | No | No | Yes | No | No | Medium |
| Rational method and time of concentration | Yes | Yes | No | Yes | No | No | Medium |
Two topics were deliberately left out of the 15 and named in the file as low priority instead. The rain gauge network and WMO density standards question appeared once, in December 2025, and seepage losses appeared twice in older sessions. Both are worth a short note in your own hand rather than a full prepared answer.
Programmes That Carry ONR 002 Basics of Hydrology
ONR-002 is a core course of the Certificate in Water Harvesting and Management and is also offered as an elective inside the BAG, BSCG and several BA Honours programmes, so the same answer file serves all of them.
Certificate students meet ONR-002 as part of their core water harvesting sequence, where the hydrology grounding feeds directly into the harvesting design courses that follow. If you are collecting material for the whole certificate, the CWHM guess Paper hub covers the other courses in the programme.
Degree students usually meet it as a discipline or generic elective, often chosen without a science background. That is precisely the group the answer structure was written for, since the file removes the guesswork about how much to write. Elective takers building a full semester set can start from the BAG guess Paper collection and add this file to it.
| Programme code | Programme name | Usual status of ONR 002 |
|---|---|---|
| CWHM | Certificate in Water Harvesting and Management | Core course of the certificate |
| BAG | Bachelor of Arts (General) | Elective chosen from the SOA basket |
| BSCG | Bachelor of Science (General) | Elective alongside the science core |
| BAECH and BAHIH | BA Honours Economics and BA Honours History | Generic elective outside the discipline |
| BAPSH and BAPAH | BA Honours Political Science and BA Honours Public Administration | Generic elective outside the discipline |
| BAPCH and BASOH | BA Honours Psychology and BA Honours Sociology | Generic elective outside the discipline |
How to Get the Full ONR 002 Basics of Hydrology Answer File
Message the number below on WhatsApp with the code ONR 002 and the complete 16 page file with all 15 answers is sent to you digitally, including the 10 answers not shown on this page.
Tell us the session you are appearing in, June 2026 or December 2026, and the programme you are enrolled in. It helps us confirm you are on the current syllabus before sending anything. Questions about the answers afterwards go to the same number, so you are not left with a file and no one to ask.
WhatsApp 9899436384 for the ONR 002 answer file
Disclaimer: Unnati Educations is a private academic support provider and is not affiliated with, endorsed by or connected to IGNOU or Indira Gandhi National Open University. This guess paper is a study aid prepared independently by our faculty and is not an official IGNOU publication. Course codes and examination details identify the subject only. Students must verify their syllabus on the official IGNOU website.
FAQs on the ONR 002 Basics of Hydrology Guess Paper
Is the ONR 002 guess paper valid for both the June 2026 and December 2026 sessions?
Yes, the file targets both 2026 term end examinations. ONR 002 follows a stable three block syllabus that has not changed across the six sessions we analysed, and the repeating topic pattern holds across June and December papers alike. The same 15 prepared answers therefore serve either session, so you can buy once and use the file for whichever sitting you appear in.
How many questions and answers are inside the ONR 002 Basics of Hydrology file?
The file contains 15 questions with complete model answers across 16 pages. Five of those answers are reproduced in full on this page as samples, which leaves 10 answers that are sent when you request the file. Every answer carries its block reference, mark value, word target and the sessions in which that topic last appeared in the paper.
Are the ONR 002 answers written from the official IGNOU study material?
Yes, each answer is written against the ONR 002 self learning material rather than from general hydrology textbooks. Definitions follow the block wording, and the counts the block gives are kept intact, so four conditions stay four and six components stay six. Figures such as the 0.70 pan coefficient and the 0.25 mm bucket tip are reproduced as the material states them.
How many questions must be attempted in the ONR 002 term end examination?
Five. The ONR 002 paper sets eight questions and instructs candidates to attempt any five, with all questions carrying equal marks of ten each against a maximum of fifty. The examination runs for two hours. Because you choose five from eight, preparing fifteen high frequency topics gives you a comfortable margin of choice inside the hall.
Does the ONR 002 guess paper cover numerical questions as well?
The file explains the methods behind the numericals, including the rational formula, time of concentration and the Thiessen polygon computation, but it does not carry a bank of solved sums. Data values change every session while the procedure does not, so working the method through on paper serves you better than memorising a particular calculation from an older paper.
Which programmes can use this ONR 002 Basics of Hydrology answer file?
Any programme carrying the course. That includes CWHM, where ONR 002 is a core course, and BAG, BSCG and the BA Honours programmes in Economics, History, Political Science, Public Administration, Psychology and Sociology, where it is taken as an elective. The examination paper is identical for all of them, so one file covers every enrolment route.
In which language are the ONR 002 answers written?
Answers are written in English. IGNOU sets the ONR 002 question paper bilingually, with the English text followed by the Hindi translation, and candidates may answer in either medium. Hindi medium students often use the English answers alongside their Hindi block, since the technical terms and the numerical values are common to both versions of the study material.
How soon is the ONR 002 file delivered after I message on WhatsApp?
Delivery is digital and usually same day during working hours. Send the code ONR 002 along with your session and programme so we can confirm you are on the current syllabus. The file arrives as a PDF you can read on a phone or print. You can also come back to the same number with doubts about any of the fifteen answers.
Is this ONR 002 guess paper an official IGNOU publication?
No. It is an independent study aid prepared by the Unnati Educations faculty from publicly available question papers and the ONR 002 self learning material. We are not affiliated with IGNOU and make no claim to represent the university. Nothing here replaces the official blocks or the assignment work required to become eligible for the term end examination.