ABSTRACT
This chapter addresses the concepts and potential roles of supplemental irrigation and water harvesting in improving water productivity and coping with increased scarcity, drought, and climate change in the dry areas. Supplemental irrigation aims to overcome the effects of drought periods as soil moisture drops and halts crop growth and development. The adoption of deficit irrigation implies appropriate knowledge of crop water use and responses to water deficits, including the identification of critical crop growth periods, and of the economic impacts of yield reduction strategies. An increase in crop production per unit of land or per unit of water does not necessarily increase farm profit because of the nonlinearity of crop yield with production inputs. Land productivity and water productivity are indicators for assessing the performance of supplemental irrigation. Water harvesting techniques may be classified into two major types, based on the size of the catchment: microcatchment systems and macrocatchment systems.
