---
title: "Hydrologic cycle with sketch"
subject: "Engineering Hydrology"
chapter: 1
key: "semester_5/engineering_hydrology:hydrologic-cycle-sketch"
source: https://www.bctengineer.com/q/semester_5/engineering_hydrology/hydrologic-cycle-sketch
site: BCT Engineering
---

# Hydrologic cycle with sketch

Engineering Hydrology · Chapter 1: Introduction

- Asked in: 2081 Bhadra, 1+3 marks; 2078 Kartik, 4 marks; 2071 Chaitra, 4 marks; 2069 Chaitra, 1+3 marks; 2066 Magh (old course), 4 marks (asked 5 times)
- Video: [Water Cycle | How the Hydrologic Cycle Works](https://www.youtube.com/watch?v=al-do-HGuIk) — National Science Foundation News
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/engineering_hydrology/hydrologic-cycle-sketch
- Whole chapter: https://www.bctengineer.com/md/semester_5/engineering_hydrology/chapter-1

## Question

Explain the hydrologic cycle in nature with the help of a neat sketch.

## Short answer

The hydrologic cycle is the continuous circulation of water between oceans, atmosphere, and land, driven by solar energy and gravity. Key processes include evaporation, condensation, precipitation, infiltration, runoff, and groundwater flow, maintaining a nearly constant global water mass.

## Answer

The **hydrologic cycle** is the continuous circulation of water between the oceans, atmosphere and land, driven by solar energy and gravity. Water changes state and place, but the total amount on earth stays nearly constant.

```text
   Sun's energy
      |
  Evaporation          Condensation -> Clouds
  + Transpiration  ^        |
      ^            |        v
 [Ocean]---------->|   Precipitation
      ^                     |
      |    Surface runoff   v
      +----- Rivers <--- [Land/Catchment]
      |                     |
      +--- Groundwater <----+  (infiltration,
           flow to sea          percolation)
```

#### Main processes
1. **Evaporation and transpiration:** Solar heat turns water from oceans, lakes and rivers into vapour. Plants release vapour through leaves (transpiration). Together they are called evapotranspiration.
2. **Condensation:** Rising vapour cools, condenses on dust nuclei and forms clouds.
3. **Precipitation:** Water returns to earth as rain, snow, hail or sleet. About 78% falls directly on oceans.
4. **Interception and depression storage:** Part of the rain is caught by leaves and small surface depressions and later evaporates.
5. **Infiltration and percolation:** Water enters the soil, and moves down to the water table to become groundwater.
6. **Surface runoff:** Rain beyond infiltration capacity flows over the ground into streams and rivers.
7. **Groundwater flow (base flow):** Water moves slowly through aquifers and feeds rivers, springs and the sea.
8. **Snow and glacier melt:** In Himalayan basins like Nepal's, snow stored in winter melts in summer and feeds rivers.

#### Importance
The cycle gives the fresh water used for drinking, irrigation and hydropower, and its study allows engineers to estimate the water available and the floods that may occur.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What drives the hydrologic cycle?
   A. Solar energy and gravity
   B. Wind and tides
   C. Earth's internal heat and gravity
   D. Solar energy and ocean currents only
   Answer: A. Sun's heat causes evaporation and gravity moves water as precipitation and runoff. (Key point: Drivers)

2. What is evapotranspiration?
   A. Evaporation from oceans only
   B. Evaporation from water and soil plus transpiration from plants
   C. Water lost by infiltration into soil
   D. Condensation of vapour on dust nuclei
   Answer: B. The answer defines it as evaporation together with plant transpiration. (Key point: Evapotranspiration)

3. When does surface runoff occur?
   A. When rain falls on the ocean
   B. When groundwater feeds a river
   C. When rain exceeds the infiltration capacity of the ground
   D. When vapour condenses in clouds
   Answer: C. Rain beyond infiltration capacity flows over the ground into streams. (Key point: Surface runoff)

4. What is groundwater (base) flow?
   A. Fast overland flow after storms
   B. Water caught on leaves
   C. Melting of snow in summer
   D. Slow movement of water through aquifers that feeds rivers, springs and the sea
   Answer: D. Groundwater moves slowly and sustains rivers between storms. (Key point: Base flow)

## Related in Engineering Hydrology

- [Hydrologic cycle and water balance equation](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Ahydrologic-cycle-water-balance) — Engineering Hydrology, chapter 1, asked 3×
- [Hydrologic cycle with sketches and its need](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Ahydrologic-cycle-sketch-need) — Engineering Hydrology, chapter 1

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