Drought

An Interdisciplinary Perspective

Ben Cook

• Publisher: Columbia University Press
• Year: 2019
• ISBN:
  9780231548908
• Topic: Physical Sciences
• Subtopic: Hydrology

Water is fundamental to all life. From the Dust Bowl of the 1930s, to the extreme water shortages that have struck California in recent years, modern societies often take its abundance for granted until it unexpectedly becomes scarce. Drought is one of the many problems anthropogenic climate change may exacerbate, but it is also a complex phenomenon at the intersection of a range of scientific disciplines and public-policy issues. In this innovative text, Benjamin I. Cook brings together climate science, hydrology, and ecology to provide a synthetic overview of drought and its environmental and social consequences.

Cook introduces readers to the hydroclimate and its components, explaining the global water cycle, the earth's climate system, and the distribution of water resources. He discusses drought dynamics and variability over time, the climatological context and ecological effects, and environmental issues such as desertification, land degradation, and groundwater depletion. He also considers the socioeconomic impacts of drought and the role of drought risk management policy, especially in light of how climate change is expected to affect drought risk and severity. Cook gives special attention to paleoclimate and the role of drought in the crises of ancient civilizations. A scientifically comprehensive and approachable overview of water issues throughout the world, Drought is a critical interdisciplinary text that will be essential reading for a broad range of students in earth science and environmental and sustainability studies.

ONE

Introduction to the Hydrologic Cycle and Drought

Water is an integral component of nearly every human and natural system on Earth, a planet unique in our solar system for its abundance of water at the surface in all three phases (liquid water, gaseous water vapor, and solid ice). Water facilitates the movement of energy and materials, provides the basis for all biological life, and serves as a critical resource for most human activities. Water is not, however, evenly distributed, and various processes affect the availability of water for people and ecosystems across seasons, regions, and time periods. Here, we review some of the most important and fundamental concepts related to the hydrologic cycle and distribution of water on Earth. How much water is there, and where is it located? What processes are responsible for moving this water around the Earth system? How much of this water is available for, and used by, people? And, finally, how do we define and measure drought?

The Global Hydrologic Cycle

The global hydrologic (water) cycle (figure 1.1) describes the continuous movement of water between and through reservoirs in the Earth system. A reservoir is any physical subdivision that contains an amount of water we can measure, whether globally (e.g., the global atmosphere or ocean) or locally (e.g., any individual aquifer or lake). Water moves between these reservoirs as fluxes that may involve transformations of water from one phase to another. For example, liquid water evaporates from the surface, becoming water vapor in the atmosphere. This water vapor, in turn, eventually condenses to ice and liquid water, forming clouds and finally returning to the surface as precipitation (e.g., rain and snow). All phase transformations of water involve exchanges of energy with the environment, making water critically important for modulating the movement of energy through the Earth system. Estimates of the global volumes of water in the m...