Tajikistan has the highest average annual precipitation in its region, along with numerous rivers, natural lakes (such as Lake Karakul), and glaciers. Most of the outdated Dushanbe water system was built during the Soviet era in 1932 and not significantly expanded afterwards even with a rising population. The Big Gissar Canal was constructed in 1942 and irrigates much of southern Tajikistan and goes from the Kofarnihon river to the Surxondaryo. As of 2004, the length of the city's water supply network was 476 km and mainly got its water from the Varzob, Kofarnikhon and the South-West. Water is supplied through two ground and two surface water treatment plants. As of 2018, 40% of the city's population did not have access to sewage systems.