The term ‘water harvesting’ is used to describe the process by which water is collected from an area that may have been modified or treated to increase precipitation runoff and is stored for later use. This chapter describes some of the methods and materials used to induce runoff in agricultural systems. Some general ideas and concepts are presented on runoff inducement techniques (such as surface modification, cover sheets, and soil surface treatment) that are feasible for use in arid and semi-arid regions of the world. The advantages and disadvantages, cost, and conditions favoring each method are discussed.