In 1990, a tunnel was built to conduct 90% of the Visočica's water back into the Lake Zavoj. That left Temštica itself without 70% of the water, leaving only the "biological minimum" to overspill from the dam. However, that is the so-called "dead water", which comes from the depth of and has the temperature of only few Celsius degrees. Without any research being conducted, in 1992 the construction of the tunnel which would conduct the waters from Temštica itself into the Lake Zavoj began. As the area of Stara Planina was protected in the meantime the project was halted.