**Dr. Ahmed Albahnasawi, Dr. Ercan Gürbulak and Dr. Mesut Tekbaş**

Department of Environmental Engineering, Gebze Technical University, Kocaeli, Turkey

**1**

a possible arid climate [3].

**Chapter 1**

**1. Introduction**

drought.

**2. Aridity**

Environment

Introductory Chapter: Arid

Arid environments cover more than one-third of the world's land area and represent the most common habitat on Earth after the oceans. Aridity poses a threat to the environment, as well as the economy, security, development, food security, and social life around the world. The causes of increased aridity are complex and are thought to be both natural and man-made. Factors such as climate change, population growth, soil erosion, inappropriate irrigation, wrong farming, soil, water, and groundwater contamination, urbanization, deforestation, improper water management, desertification of arid and semiarid zones appear as causes of

This book covers a wide range of scientific research studies, from water management to groundwater management, from land rehabilitation to soil reclamation, which will help prevent and minimize man-made aridity. In addition, many studies related to aridities such as environmental education, environmental awareness, sustainable development, and management policies and plans are also welcome.

Aridity is the imbalance between the long-term average water supply and the long-term average water demand [1]. Unlike drought, which is defined as a period of abnormally dry air long enough to cause a serious hydrological imbalance, aridity is permanent, not temporary. Aridity is a condition in which the amount of usable water in an area is reduced to such an extent that it hinders or prevents the growth and development of plants and animals. Regions with arid climates lose or tend to lose their vegetation. These regions, which are generally located close to the equator, are called xeric, arid, or desert according to their aridity levels. In the more extreme areas, called extreme arid deserts, the average annual precipitation is below 25 mm, under which conditions microorganisms must cope with not only by water scarcity but also by deadly UV radiation, high and low temperatures, high evaporation rates, prolonged drying times, oligotrophic conditions, and high salinity levels. Aridity is often evaluated with the aridity index (**Table 1**) and aids in determining whether there is a water shortage in the region and deciding the measures to be taken in case of

*Murat Eyvaz and Ahmed Albahnasawi*
