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The North-South Carrier (NSC) is a pipeline in Botswana that carries raw water south for a distance of to the capital city of Gaborone. Phase 1 was completed in 2000. Phase 2 of the NSC, under construction, will duplicate the pipeline to carry water from the Dikgatlhong Dam, which was completed in 2012. A proposed extension to deliver water from the Zambezi would add another to the total pipeline length. The NSC is the largest engineering project ever undertaken in Botswana. ==Climate== Botswana has an arid climate, with little in the way of surface water supplies. Until recently, groundwater wells were used to meet about 80% of demand for water. Some of the groundwater accumulated long ago when the climate was wetter. "Groundwater mining" is not sustainable in areas where the water is not being renewed from the surface. The more populous eastern portion of Botswana lies in the Limpopo River basin, which is considered "closed". In the South African portion of the basin, water usage exceeds the potential water yield from the basin by 800,000,000 cubic metres (2.8×1010 cu ft) annually. Water has to be imported from the Vaal River to make up the shortfall. Almost all rainfall occurs in the summer months of October through April, at a time when temperatures over cause high levels of evaporation. Rainfall is undependable. A drought period may last for several years. Precipitation is highest in the northeast, at about annually, and lowest in the southwest, at about annually. Annual average potential evaporation is about annually. Botswana has flat terrain that is mostly unsuitable for reservoirs. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「North-South Carrier」の詳細全文を読む スポンサード リンク
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