Lake Tharthar (also Therthar), and known in Iraq as Buhayrat ath-Tharthar (Arabic: بحيرة الثرثار‎), is a lake situated 120 kilometers north of Baghdad between the Tigris and the Euphrates rivers. It is the largest lake in Iraq. The construction of several dams has made it an important source for irrigation. Its size shrinks and expands dramatically with the seasons. The lake is deep and nutrient poor; there is very little vegetation except for sparse shrubs, some dense patches of growth and scattered Ziziphus trees. The area is farmed thanks to the use of tube-wells. A few sheep also graze in the area. The lake is threatened due to overfishing.