Effect of Shahid Kalantari Causeway on Urmia Lake Depth Decrease

In Holoccene, Urmia Lake has never been a playa sedimentary environment. It was a saline lacustrine sedimentary environment. Therefore, problem solution of Urmia Lake is different from other lakes. Historical backgrounds indicate that this lake has had a depth more than 13m up to 1992. In dry seasons, the lake did not indicate playa sedimentary environment. But, Urmia Lake has been converted into playa sedimentary environment in current conditions. Hence, to restore Urmia Lake, the procedure should convert the playa sedimentary conditions to saline lacustrine sedimentary environment (≥350gr/lit salt concentration) which has been produced in a period of several thousand years. Sedimentation rate of evaporative minerals which are dominantly halite or salt increases by minerals concentration. Based on hydro geochemistry of brine and geochemistry of Lake floor sediments, it should be very essential to consider the water supply method of the lake. In the past, Urmia Lake was a lake having its maximum depth in the central part, but today its environment has converted into a playa and a salt pan. Therefore, a fundamental procedure must be applied. Considering that high concentration of brine can produce thick evaporative minerals (salt) in the lake floor, water re-supply by water having dissolved minerals can solve deposited salts in the lake floor, and then it will produce high concentration saline waters again. This brine re-deposit with more precipitation rate. Therefore, Urmia Lake problem will not be fundamentally solved. Decrement of the lake area with regard to its available volume of water, salt removal from every region before fresh water inputting process will be the best method to save the lake and prevention from freshwater waste in the region. Shahid Kalantari Causeway Bridge restricted water flows by making only one bridge and imposed a relative calmness to the lake. On the other hand, Urmia Lake sedimentary environment is dual sedimentary environment having dominant chemical deposits. These sediments were dominantly carbonates but at present evaporative sediments are more significant. In a carbonate sedimentary environment which carbonate mud, particularly aragonite is precipitating a kind of relative calmness is visible and significantly increase the sedimentary rate up to hundreds of normal conditions. Sedimentary rate of Urmia Lake is between 0.15 to 1mm and the average of 0.5mm per year. It seems that making Shahid Kalantari Causeway Bridge increased sedimentary rate and as a result carbonate sediments quickly deposited in the lake floor. Therefore, the relatively deep floor of the lake converted into a relatively unsmooth floor.If it is proved that making Shahid Kalantari Causeway Bridge increases the sedimentary rate from 0.5mm to 50cm, it means that sedimentary rate has increased up to 100times). In fact, 100-year changes of the lake have been done only in a year.