Tajikistan is a mountainous country; the Tian Shan, Gissar-Alay and Pamir mountain systems cover about 93% of the country with half of it lying above 3 000 m. Lowland areas are confined to river valleys in the southwest and to the Ferghana Valley in the north.
Tajikistan is rich in water resources. It has about 1 300 lakes, most of which are located above 3 000 m in the eastern Pamir region. The largest one is the saltwater Lake Karakul (380 km²), at an elevation of 3 914 m. The deepest freshwater lake is the 490m-deep Lake Sarez (3 239 m above sea level, 86.5 km²), which was formed after an earthquake in 1911 triggered a landslide that formed a natural dam blocking the Murghab River.[This river called Murghab is not to be confused with another river named Murghab that is shared between Afghanistan and Turkmenistan in the Harirud/Murghab Basin.] Experts fear that the natural dam might breach or that landslides could cause a tidal wave over the dam in case of an earthquake, which could result in a catastrophic flooding along the Panj and Amu Darya. Glaciers cover 6% to 8% of the state, and 90% of them lie in the Amu Darya Basin.
More than 25 000 rivers flow in the country. Tajikistan forms part of both the Syr Darya and the Amu Darya Basins, which cover practically the entire country. The rivers Vakhsh, Kafirnigan and the Panj, the border river with Afghanistan, are the main tributaries to the Amu Darya, fed by glacier and snowmelt from the high ranges of the Pamir mountains and draining more than 75% of the country. In the northern Ferghana Valley, the Syr Darya crosses 195 km through Tajikistan. Another important transboundary river is the Zarafshan, which runs through central Tajikistan into Uzbekistan.Tajikistan has nine operating reservoirs, most of them along the Vakhsh River, which feeds the Amu Darya.
Even though only 5% of Tajikistan's land area is arable, irrigation agriculture plays an important economic role and produces 90% of the agricultural output. More than 60% of the land depends at least partly on pumped irrigation, which makes it more expensive than in other Central Asian countries. Cotton constitutes 43% of all planted crops. Though the share of agriculture in GDP declined from 37% in 1991 to 22% in 2009, cotton still yields 11% of all exports, which makes it the most important export after aluminium and electricity. As for the workforce, about 31% (2004) is officially engaged in agriculture.
Tajikistan's main water usage is hydropower production. After Russia, Tajikistan is the second largest producer of hydropower in the CIS; on a per capita basis it is the biggest worldwide, despite the fact that at present only about 5% of the hydropower potential is exploited. The biggest hydropower plants are: Nurek (3 000 MW), Sangtuda 1 (670 MW), Sangtuda 2 (220 MW), Baipazan (600 MW), Golovnaya (240 MW) and Kairakum (126 MW).
But this production is not enough to meet the energy demands of the country. Like Kyrgyzstan, Tajikistan used to receive coal and gas in the Soviet unified system and faces a severe energy crisis today. In winter, rural areas usually have power for only a few hours a day. In the winter 2010/11, even in the capital the electricity supply was restricted. The problem is aggravated by the fact that much of the energy that is produced is consumed by the big aluminium plant TALCO or gets lost in inefficient transmission systems. In this respect, the government strives to make more use of its rich hydropower potential. In addition to about 250 small hydropower plants, several new large one have been constructed since independence, such as the Sangtuda 1 and 2 on the Vakhsh River, supported by Russian and Iranian investments.
The Tajik government has also revived old plans to build the highest dam in the world at Roghun, with a planned height of 335 m and a power plant designed to produce 3 600 MW of electricity. The construction of this dam was started in the 1980s, but construction stopped and it was damaged by a flood in the early 1990s. In October 2004, the Tajik government entered into an agreement with the Russian company RusAl to construct the first stage of Roghun, but due to disagreements about the height of the dam, it was cancelled by Tajikistan in August 2007. In 2009, Tajikistan decided to finance the dam itself. In January 2010, it introduced shares of Roghun with a massive campaign urging the population to buy them. In the following months, shares worth $ 185 million were sold. After concerns were raised by downstream countries, Tajikistan agreed to carry out an independent assessment of the technical feasibility and the social and environmental impacts of the project by international experts financed by the World Bank. Until the results are released in mid-2012 at the earliest, Tajikistan is committed not to resume construction.[AsiaPlus 2011, BIC 2011, Sehring 2009, UNDP 2003, UNECE 2004, WDI, WRI.]