Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Soil Processes
- Part IV Hydrometeorology
- 11 Water balance
- 12 Watershed hydrology
- 13 Surface energy fluxes
- 14 Turbulent fluxes
- 15 Soil moisture and the atmospheric boundary layer
- Part V Biometeorology
- Part VI Terrestrial Plant Ecology
- Part VII Terrestrial Forcings and Feedbacks
- Index
- Plate section
- References
11 - Water balance
from Part IV - Hydrometeorology
- Frontmatter
- Contents
- Preface
- 1 Introduction
- Part I The Earth System
- Part II Global Physical Climatology
- Part III Soil Processes
- Part IV Hydrometeorology
- 11 Water balance
- 12 Watershed hydrology
- 13 Surface energy fluxes
- 14 Turbulent fluxes
- 15 Soil moisture and the atmospheric boundary layer
- Part V Biometeorology
- Part VI Terrestrial Plant Ecology
- Part VII Terrestrial Forcings and Feedbacks
- Index
- Plate section
- References
Summary
Chapter summary
The cycling of water between Earth's surface and the atmosphere involves an exchange of mass (water) and energy. Energy exchange occurs because considerable amounts of energy are needed to evaporate water. This energy is released when water vapor in the air condenses to liquid. This chapter is an introduction to the hydrologic cycle on land. The overall hydrologic cycle is reviewed and simplified into an expression where the change in soil moisture is the balance between precipitation input and losses from evapotranspiration and runoff. The various terms in this equation are discussed in detail. Not all precipitation reaches the ground. Some precipitation is intercepted in the plant canopy and evaporates back to the atmosphere. Evaporation is the physical process by which liquid water is changed to vapor. Transpiration is the evaporation of water held internal to plants as water moves from the soil through plants into the atmosphere along a continuum of decreasing water potential. The basic meteorological and biological processes controlling evapotranspiration are introduced, but a more in-depth discussion of meteorological processes is found in Chapters 13 and 14, and the biological control of transpiration by leaves and plant canopies is reviewed in Chapters 17 and 18, respectively. Runoff is discussed in separate sections on infiltration and overland flow. The Green–Ampt equation and Philip's equation illustrate the physics of infiltration and show the dependence of infiltration rate on soil texture and antecedent soil moisture.
- Type
- Chapter
- Information
- Ecological ClimatologyConcepts and Applications, pp. 155 - 169Publisher: Cambridge University PressPrint publication year: 2008