It is said in Adi-purana that one who takes bath in Sankarshan-kund is freed from the sin of killing the cow. If you speak with the pujaris they will tell you that the lake has power to cure any diseases. All you need to do is take bath every day for one month in the lake.
When Krsna was holding the hill aloft, He was concerned about the waters rising all around. Krsna was personally taking care of the water coming down on the hill using His Sudarshana disc as a fiery shield, so even Govardhana was not being affected by the torrential rains, but there was still some water rising from the rest of the area around. So He asked His elder brother Balarama to take care of the remainder. Douji in the form of Ananta Sesa then collected the rest of the waters thereby forming Sankarshan kund.