Key Questions in Hydrology and Watershed Management

A Study and Revision Guide

Leon Bren, Patrick Lane

• Éditeur: CAB International
• Année: 2021
• ISBN:
  9781789249705
• Sujet: Physical Sciences
• Sous-sujet: Hydrology

This book provides a series of exercises of various types covering matters of hydrology and watershed management. The exercises include true/false questions, multiple choice questions, and numeric, graphical, and analytical exercises. The questions draw on the basic disciplines of hydrology and physics, with some stress placed on correct or appropriate units. The questions reflect the authors' many years of teaching watershed management at undergraduate and graduate levels.Questions cover: 1. Terminology and measurement of flow (and units)2. Quantifying stream networks3. Concepts of water balance and evapotranspiration4. Slope recharge, groundwater hydrology, and water-table/phreatic aquifers5. Single and paired watershed experiments6. Impacts of fires on watersheds7. Concepts and measurements of water quality8. Flooding forests9. Valuation of water10. Protection of forest stream by buffers11. Urban watershed conceptsThe book is self-contained, and designed to be used at any time in any place, either for revision or as source material for teaching. The work is graded so that easier questions are presented early, followed by harder questions. Answers are concise but contain enough information to help students study and revise on a topic-by-topic basis. The book concludes with suggestions for student exercises and projects and is an invaluable resource for both students and instructors.

1 Multiple Choice Questions

For most questions, tick answers which you think are ‘True’ or ‘Correct’. This may range from zero to all answers. Some cases will specify the number of answers, and some will ask you to pick out an incorrect statement. It is requested that you think carefully before looking up the answers. Please also be aware that in hydrology differences tend to be ‘shades of grey’ rather than black and white. We hope that you find such questions a useful vehicle for fruitful discussion with your lecturers rather than outrage that the authors are so incorrect. The answers provide a brief commentary on the logic.

Units

1. A megalitre denotes a million litres. Which abbreviation is correct for this amount of water?

A. ml

B. MLi

C. ML

D. mL

2. 20 ML ha^-1, as rainfall, is the same as which of the below?

A. 1 mm of rain

B. 100 mm of rain

C. 1000 mm of rain

D. None of the above

3. In the older unit of ‘points’ of rain, there are 100 points to the inch. One inch is 25.4 mm. Hence 20 points of rain is about equivalent to which of the answers below?

A. 1 mm

B. 5 mm

C. 100 mm

D. None of the above

Dimensions

4. A fundamental division in science is mass [M], length [L], and time [T]. Most (but not all) physical quantities can be ascribed dimensions such as force [MLT^-2], representing the product of mass [M] by acceleration [LT^-2]. Which of the following attribution of dimensions to hydrologic variables is correct?

A. Rainfall intensity [L³T^-1]

B. Streamflow [L³T^-1]

C. Rate of evaporation [L²T^-1]

D. Volume of channel storage per unit length of channel [L³]

Strahler Ordering

5. One of the statements about Strahler order notation used for classifying waterways is incorrect. Which one?

A. The order assigned will depend on the diligence of map-makers in showing smaller streams

B. Major rivers such as the Mississippi, Danube, or the Amazon will be sixth-order or higher

C. Headwater streams originating on farms are going to be first or second-order

D. All water courses can be assigned a unique Strahler order

6. Which two of the following statements are correct about Strahler ordering of watersheds?

A. When a lower-order stream joins a higher-order stream, the order of the resulting stream increases by one

B. When a lower-order stream joins a higher-order stream, the order of the resulting stream stays the same

C. When two streams of the same order join, the order of the resulting stream increases by one

D. By definition, streams of the same order cannot join

7. Using Strahler ordering, a third-order stream is joined by two second-order streams and three first-order streams. The new stream is then?

A. Second-order

B. Fourth-order

C. Third-order

D. Fifth-order

E. None of the above

Hydrographic Measurement

8. The functions of a weir pond behind a measurement section are which of the following?

A. To allow water to approach the measurement section with a minimum velocity

B. To conserve the biota of a stream

C. To reduce turbulence at the point of measurement

D. To reduce the noise of the water outflow

E. To give the water enough height to allow it to fall free of the measurement cross-section

9. Measurement weirs are a favourite method of gauging small, upland streams. A ‘stream-rating’ is a 1 to 1 relation between flow through a measurement weir and height of water above the notch. Many factors may lead to a deviation from such a relationship. One in the list below should not affect the rating – which one?

A. Water temperature

B. Sediment in the water

C. Aeration status of the water

D. Changes in the weir pond

E. Changes in the stream channel below the weir

10. The concept of a ‘hydrologic year’ is sometimes used in hydrologic data analysis with the start of the year somewhere near the end of summer. Which listed advantages below are correct?

A. With this division of the year, there is less correlation between what happens in a given year with what happened in the preceding year because the watershed soil moisture is usually close to minimum

B. It sits better with the annual political cycle of many countries

C. It allows a better pairing of annual rainfall with annual streamflow

D. It best matches the annual irrigation cycle in many countries

E. Judicious choice allows ‘meshing’ with the financial year of many countries

11. A diurnal variation is a characteristic stream flow variation with a 24-hour cycle. Which of the following statements are correct?

A. In a non-snow watershed, transpiration by trees will often give a diurnal variation with a day-time minimum and a night-time maximum

B. Diurnal variations are a major periodic component of the hydrologic cycle.

C. In a watershed with snow cover, the melting of snow by the sun will give a diurnal variation with a day-time maximum and a night-time minimum

D. Diurnal variations in streamflows are often obscured by the bi-diurnal tidal cycle associated with the passage of the moon over the earth’s surface

E. Diurnal variations are only found in first and second-order streams

F. They are sometimes referred to as Diehl variations

12. Consider water travelling across the earth’s surface, with the lower part of the water body in contact with the earth and in equilibrium (i.e. not falling). What is about the fastest documented speed that the water will travel at?

A. 10 kph

B. 30 kph

C. 70 kph

D. 100 kph

E. 200 kph

13. Which three of the following are necessary to develop a stream rating for hydrographic purposes?

A. A method of accurately measuring the volumetric rate of flow of a stream at a given time

B. A good working knowledge of Manning’s Equation, its errors, and how it is applied

C. A local measure of water height based on a permanent and accessible reference point

D. A good working knowledge of Bernoulli’s Equation

E. A stable cross-section which does not have discontinuities in it

F. A method of smoothing the flow to avoid turbulence

Soil Moisture and Vadose ...