Because of the great importance of coriander (Coriandrum sativum L.) plants as natural sources for producing the volatile oil which has several uses in pharmaceutical and food industries, more investigations for improving the growth and productivity of this plant are still needed. Irrigation is a very important factor affecting the growth and yield of medicinal and aromatic plants. Irrigation also may affect the volatile oil composition. From another point of view, water is characterized as such no alternative source can substitute it and it is not a commercial resource or commodity. It is known that Egypt is a downstream country of the Nile River. Based on this fact, the great challenge for the coming decades will be the task of increasing the productivity of water units ( Abdin and Salem, 2009). Irrigation as an environmental factor has an important role in plant growth and is essential to increase yield and quality of plants ( Singh and Goswamy, 2000). Deficit irrigation, one of the environmental stresses, is the most significant factor restricting plant growth and crop productivity in the majority of agricultural fields of the world ( Abedi and Pakniyat, 2010). Identifying growth stages of a particular cultivar under local conditions of climate and soil fertility allows irrigation scheduling to maximize crop yield and most efficient use of scarce water resources ( Mahal and Sidhu, 2006).