Physical Hydrology

Citation

Dingman, S. L. (2015). Physical Hydrology (3rd ed.). Waveland Press.

Chapter Summary

The book runs to about 640 pages in three parts: an introduction (Chapters 1–2), the exchange of water and energy between the atmosphere and the land surface (Chapters 3–6), and the movement of water on and through the land (Chapters 7–10). Seven appendices follow. The publisher describes the organising themes as the basic concepts of hydrology, the surface–atmosphere exchange of water and energy, and the land phase of the hydrologic cycle, with each analytical approach presented together with its assumptions and limitations.

Chapter 1: Hydrology: Basic Concepts and Challenges

The opening chapter defines the scope of hydrology and the approach of the book. Its sections cover physical quantities and laws, dimensions and units, the properties of water, hydrologic systems and the conservation equations, the watershed and the regional water balance, the special characteristics of hydrologic variables, hydrologic storage and uncertainty. It closes with the use of these ideas to model how a watershed functions, and with the future of hydrology.

Chapter 2: The Global Context: Climate, Hydrology, and the Critical Zone

A short chapter placing the subject in its planetary setting: basic aspects of global climate, the global hydrologic cycle, and the relation of hydrology to the critical zone.

Chapter 3: Principles and Processes

The first chapter of Part II sets out the physics needed for the surface–atmosphere exchange: pressure–temperature–density relations, water vapour, the evaporation process, and the turbulent exchange of momentum, mass and energy.

Chapters 4–5: Precipitation; Snow and Snowmelt

Chapter 4 treats precipitation through meteorology, measurement, estimating areal precipitation from point measurements, and precipitation climatology. Chapter 5 gives snow its own chapter: its hydrologic importance, material characteristics, measurement and distribution, snowmelt processes, snowmelt runoff generation and snowmelt modelling.

Chapter 6: Evapotranspiration

Evaporation and heat-exchange processes lead to a classification of evapotranspiration processes, then to free-water and lake evaporation, bare-soil evaporation, transpiration, and interception loss. The chapter ends with potential and reference-crop evapotranspiration and with actual evapotranspiration.

Chapters 7–8: Principles of Subsurface Flow; Infiltration and Water Movement in Soils

Part III begins below the surface. Chapter 7 covers the material properties of porous media, water storage, and the basic principles of saturated and unsaturated flow. Chapter 8 applies them to soils: soil-water conditions, the infiltration process and its measurement, quantitative modelling of infiltration at a point and over areas, and the redistribution of soil water.

Chapters 9–10: Ground Water in the Hydrologic Cycle; Runoff Generation and Streamflow

Chapter 9 deals with aquifers and aquitards, regional ground-water flow, ground-water–surface-water relations, the ground-water component of the regional water balance and the effects of ground-water development. Chapter 10 follows water to the stream: the watershed and stream network, stream response, the identification of runoff sources, event-flow generation, channel processes and rainfall–runoff modelling.

Appendices A–G

The appendices cover measurement precision, significant figures and unit conversion; water as a substance; statistical concepts useful in hydrology; estimation of daily clear-sky incident solar radiation; stream-gauging methods for short-term studies; hydrologic simulation modelling; and the development of scientific hydrology.

Key Concepts

Chapters 1–2: Foundations

• Conservation equations and the water balance: hydrologic systems are described by conservation of mass, applied to a watershed or a region.
• Hydrologic storage and uncertainty: the book treats stores of water and the uncertainty in hydrologic estimates as basic features of the subject.
• Critical zone: the near-surface layer in which hydrology, climate and ecosystems interact.

Chapters 3–6: Surface–atmosphere exchange

• Turbulent exchange: the transfer of momentum, mass and energy that drives evaporation.
• Areal estimation: deriving area-wide precipitation from point gauge measurements.
• Snowmelt: the processes and models that convert a snowpack into runoff.
• Potential, reference-crop and actual evapotranspiration: successive levels of evapotranspiration estimation.

Chapters 7–10: Water on and in the land

• Saturated and unsaturated flow: the two regimes of water movement in porous media.
• Infiltration: the entry of water into soil, modelled at a point and over an area.
• Regional ground-water flow and the ground-water balance: aquifers considered as parts of the wider water balance.
• Runoff generation: the processes by which rainfall or snowmelt becomes streamflow, and the models that represent them.

Critical Analysis

Strengths

• Clear three-part structure. The chapters follow the water: global context, then exchange with the atmosphere, then movement across and below the surface. A reader can see where each chapter sits in the overall cycle.
• Assumptions and limits stated. The publisher stresses that the author describes the assumptions behind each analytical approach and identifies its limitations, which is useful for students who will apply the equations.
• Attention to change. The publisher highlights an examination of documented trends in global change of climatic and hydrologic quantities, so the book connects the physical principles to climate and land-use questions.
• Worked examples and practical material. A reviewer quoted by the publisher singles out the boxes with examples and calculations; the publisher also lists additional exercises based on data sets from the Internet and downloadable Excel spreadsheets.
• Useful appendices. Measurement and units, statistics, solar-radiation estimation, stream gauging and simulation modelling are collected in appendices, so the main chapters can concentrate on the physics, and a final appendix on the history of scientific hydrology gives context.

Limitations

• Length and density. At about 640 pages, the book holds more than a single introductory course can cover, and it is quantitative throughout. Instructors and self-study readers need to select chapters.
• Land phase only. The scope is the land phase of the hydrologic cycle. The chapter titles show no separate treatment of water quality or of water-resource management, so those topics need other books.
• Prerequisites not stated by the publisher. The publisher's page does not list required background; the quantitative treatment points to calculus, introductory physics and basic statistics, and readers without them will find the early chapters demanding.

Where It Fits in the Course

Within the course's reading list, this is the detailed, quantitative treatment of hydrology. Hendriks's Introduction to Physical Hydrology is a compact introduction for geography and earth-science students that takes atmospheric water, groundwater, soil water and surface water in turn with worked examples; it is the sensible first book, and Dingman is the book to move to for derivations, measurement methods and modelling.

The geomorphology books cover the landforms that water shapes. Huggett's Fundamentals of Geomorphology and Bierman and Montgomery's Key Concepts in Geomorphology are broad introductions, and Goudie and Viles's Landscapes and Geomorphology: A Very Short Introduction is a brief overview; Anderson and Anderson's Geomorphology: The Mechanics and Chemistry of Landscapes is the closest in method, since it builds landscape processes from conservation laws. Dingman's Chapters 9–10 on groundwater and streamflow pair naturally with the fluvial chapters of these texts.

How to Use This Book

The book suits upper-level undergraduates, graduate students and practitioners in geography, earth science and engineering who need a quantitative grounding in hydrology. Calculus, introductory physics and some statistics are the sensible preparation.

A practical plan for a one-semester course:

• Core: Chapter 1 and the sections of Chapter 2 on the hydrologic cycle, then Chapters 4, 6, 8 and 10, which together follow water from precipitation to streamflow.
• Add as needed: Chapter 3 for the physics of evaporation, Chapter 5 for snow-dominated regions, Chapter 7 before Chapters 8–9, and Chapter 9 for groundwater.
• Reference: the appendices, especially C on statistics, E on stream gauging and F on simulation modelling, as projects require them.

Work the example boxes before attempting the exercises, and use the spreadsheets and data-set exercises to practise with real data. A reader new to the subject can read Hendriks first and return to Dingman by chapter.