Unit 1: Introduction to Hydrology

Question 1

Define Hydrology

Answer 1

The science concerned with the occurrence, distribution, movement and properties of water.

Question 2

Why is a good understanding of hydrological processes important? (2)

Answer 2

It is important for:
1. The assessment of water resources.
2. The management and conservation on regional and global scales.

Question 3

What are the issues Hydrologists are concerned with (3)

Answer 3

1. Water use - for water resource planning and management
2. Water control - to control extremes (floods, erosion, etc.) and the development of guidelines for the protection of floodplains and stormwater detention
3. Pollution control

Question 4

Name the 8 key processesof hydrological cycle

Answer 4

1. Evaporation
2. Condensation
3. Precipitation
4. Transpiration
5. Infiltration
6. Percolation
7. Runoff
8. Groundwater flow

Question 5

What is the ratio of saltwater to freshwater and how much is usable?

Answer 5

97% of the earth’s water is salt water and 3% is freshwater, of which only 0.3% is usable.

Question 6

What is the relationship of water to transport and rock cycles?

Answer 6

Water acts as a transportation agent, carrying suspended and dissolved materials, including fragments of rock. Acid rain dissolves rock fragments, which are then transported by rivers to the ocean, where they consolidate to form sedimentary rocks.

Question 7

Define the carbon cycle

Answer 7

It refers to the storage and exchange of carbon between the atmosphere (air), hydrosphere (waterbodies) and geosphere (ground).

Question 8

Describe the main processes involved in the carbon cycle (3)

Answer 8

1. The uptake of carbon in the form of CO2 by plants through the process of photosynthesis. It’s released back into the atmosphere through the processes of respiration and decomposition.
2. The balance between dissolution of carbon dioxide into the sea and the release back into the atmosphere.
3. The weathering and dissolution of carbon-rich rocks.

Question 9

Name the types of waterbodies (2)

Answer 9

• Standing (Lentic)
• Running (Lotic)

Question 10

Complete the diagram on the various forms of water.

Answer 10

See notes

Question 11

What were the advancements in Hydrology over the following time periods: 8th century BC, 1st century, late 15th century, 17th century, 18th century, 19th century, early 20th century and after the 1950s

Answer 11

• 8th century BC: Homer believed in the existence of large subterranean reservoirs that supplied rivers, seas, springs and wells.

• 1st century BC: Roman engineer Marcus Vitruvius developed an early theory of the hydrologic cycle in his paper ‘On Architecture’.

• Late 15th century: Leonardo da Vinci and Bernard Palissy gave, independently of each other, an accurate explanation of the hydrologic cycle.

• 17th century: modern science of hydrology was established by Perrault, Mariotte and Halley.

• 18th century: The Bernoulli piezometer and theorem, the Pitot tube and Chezy’s formula.

• 19th century: Darcy’s law of flow in porous media and
Dupuit-Thiem’s well formula were elaborated.

• Early 20th century: governmental agencies developed their own programs of hydrologic research. Sherman’s unit hydrograph, Horton’s infiltration theory and Theis’s non-equilibrium approach

• After 1950: the progress in sciences and the high-speed digital computers opened new perspectives in hydrology. Hymsim (rainfall-runoff model), HEC-RAS (Hydraulic modeling and analysis software) & ArcGIS (Mapping and spatial analysis)