How to keep scallions fresh?

I bought a lot of scallions before Ied, hoping that they would stay fresh till the rest of the week. The traffic must be crazy out there and I don't want to stuck in the street. So, I goggled and found a tip about keeping my scallion. The page says that I should put my scallions in water as deep as the white part of the spice. I need to change the water every day. 

However, after the 3rd day, I spot some dry leaves. And the scallions turn smelly. Hmm, it doesn't work, people. So, I put the rest of scallion to a jar and keep it in refrigerator. It's already a week and I still have it green.