Practically the entire drainage system of Afghanistan is enclosed within the country. Only the rivers in the east, which drain an area of 32,000 square miles, reach the sea. The Kabul River, the major eastern stream, flows into the Indus River in Pakistan, which empties into the Arabian Sea of the Indian Ocean. Almost all the other important rivers of the country originate in the Central Highlands region and empty into inland lakes or dry up in sandy deserts. The major drainage systems are those of the Amu, Helmand, Kabul, and HariRoad.
The Amu, a 1,578-mile-long river originating in the glaciers of the Pamirs, drains an area of approximately 93,000 square miles in the northeastern and northern parts of the country. It forms the frontier between Afghanistan and the republics of Tajikistan and Uzbekistan for about 600 miles of its upper course. Two of its major Afghan tributaries, the Kowkcheh and the Qonduz, rise in the mountains of Badakhshan and Konduz provinces. The Amu becomes navigable from its confluence with the Kowkcheh, 60 miles west of the city of Feyzabad. It empties into the Aral Sea in Uzbekistan.
The northwestern drainage system is dominated by the HariRoad River, originating on the western slopes of the Baba Mountains, at an altitude of 9,000 feet. The river flows westward, just south of Herat and across the broad Herat Valley. After irrigating the fertile lands of the valley, the Hari River turns north about 80 miles west of Herat and forms the border between Afghanistan and Iran for a distance of 65 miles. It then crosses into Turkmenistan and disappears in the Kara-Kum Desert.
The principal river in the southwest is the 715-mile-long Helmand, which rises in the Baba Mountains, about 50 miles west of Kabul. With its many tributaries, mainly the Arghandab, it drains more than 100,000 square miles. The river empties into the Saberi, an inland lake. In its course through the southern region of the country, the Helmand flows north of the Rigestan Desert and then crosses the Margow Desert until it reaches a region of seasonal lakes in the Sistan depression.
The largest drainage system in the southeastern region is that of the Kabul River, which flows eastward from the slopes of the Mazar Range to join the Indus River at Attock, Pak. Its major tributary in the south is the Lowgar.
Afghanistan has few lakes of any considerable size. The two most important are Lake Saberi in the southwest and the saline Lake Istadeh-ye Moqor, situated 60 miles south of Ghazni in the southeast. There are five small lakes in the Baba Mountains known as the Amir lakes; they are noted for their unusual shades of colour, from milky white to dark green, caused by the underlying bedrock.