Feasibility Study of Transbasin Diversion through Alborz Tunnel towards South Hillside of Alborz Mountain

In this report, the transbasin diversion through Alborz tunnel towards southern hillside of Alborz mountain has been studied. Alborz tunnel has been excavated so that the southern portal is located in the southern hillside of Alborz mountain, in the Karaj river basin, while the northern portal is located in the northern hillside, in the Chalous river basin. Alborz tunnel is located in the under construction highway between Tehran and Chalous and so, the main purpose of this tunnel is transportation one. Field observations indicate that some water resources nearby the northern tunnel portal (in Chalous river basin) can be diverted to the Karaj river basin through this tunnel. Water shortage in the southern hillside of Alborz mountain is the reason of this idea. A lot of groundwater is already seeping into the Alborz tunnel and due to the northward slope of tunnel, this water is ended to the Chalous basin. In addition to this seeping water, there are two surface flows nearby the northern tunnel portal which can be diverted to the southern hillside through the tunnel. The scope of this study is the feasibility study of diversion of these three water flows to the southern hillside through Alborz tunnel. The most important achievements of this study can be summarized as follow: - Groundwater seepage into tunnel has the flux about 0.3 m3/sec. - The total available water resource nearby the north Alborz tunnel portal which can be diverted to the south hillside is about 1 m3/sec. - Groundwater basin of tunnel has spread over the Khakak and Sarkhas mountains with the area about 20.3 km2. - The negative effect of tunnel excavation on water resources in north is due to dewatering some springs and decreasing water flux in Kandovan- Lan river, effecting some small scale agricultural activities. - The negative effects of water diversion on the north hillside are due to disturbances in two important projects, means “Overall exploitation of costal rivers in Mazandaran Province” and “Siahbisheh power station project”. - In case of water diversion through the tunnel, water pollution due to Douna river must be considered. - Oil pollutants in exiting water from Alborz tunnel is also an important problem that must be taken into account in case of water diversion. In an overall looking to the idea about water diversion through Alborz it can be said that this water diversion is not reasonable. The most important reason of this negative answer is disruption of this water diversion in the project of “Overall exploitation of costal rivers in Mazandaran Province” and “Siahbisheh power station project”.