## Muhammad Al-Karaji: A Mathematician Engineer from the Early 11th Century

Abu Bakr Muhammed Al-Karaji is a Muslim mathematician and engineer from the late 10th century-early 11th century. Of Persian origin, he spent an important part of his scientific life in Baghdad where he composed ground breaking mathematical books. Al-Karaji is also the author of Inbat al-miyah al-khafiya (The Extraction of Hidden Waters), a technical treatise that reveals such a profound knowledge of hydrology that it should be celebrated as the oldest text of its kind in this field. The book provides an outstanding study on the different kinds of waters, the methods to find the water level, the description of instruments for surveying, the construction of the conduits, their lining, protection against decay, and their cleaning and maintenance. In this article the scientific work of Al-Karaji is characterized, details of his biography are surveyed and a special attention is paid to expound the contents of his treatise of hydology.