According to Icelandic news there is little water in small streams that come from Hekla volcano. This lack of water in streams from Hekla volcano is often looked as indicators that a eruption is going to happen in coming months. This phenomenon has happened before a eruption took place in Hekla volcano, the last one that took place in the year 2000. But according to old news article (in Icelandic, pdf) (from the year 1995) this phenomenon was also observed before the big eruption in the year 1755. But I do not know if this happens always (it seems to do so. But I don’t have it confirmed) or just before some eruptions.
There has been drought in the area. But that might explain in part this lack of water in streams coming from Hekla volcano. But the rest of this lack of water might be related to changes in the area before Hekla volcano starts erupting. Far as I know there has not been any study into this phenomenon and why this happens to Hekla streams months before eruption takes place.
Hekla volcano does not give many long term signals on when it might start erupting. But far as this one goes, this might be the best signals we can get on the impending eruption in Hekla volcano. When the eruption might take place is impossible to know at current time.
Vatn er lítið í ám og lækjum nærri Heklu (Vísir.is, Icelandic)
Low Water Levels Indication of New Iceland Eruption? (English, Iceland Review) – Thanks to Erik at Eruption blog for this link!
Blog post updated at 04:19 UTC. A english news added.