From Meltina take trail nr. 4 to Vallesina, then trail nr. 4 and 2 to San Giorgio, from there continue the trail to Frassineto. From Frassineto take the trail nr. 4B and 12 A to the water reservoir, then left the trail nr. 10 to Meltina.
Or you can take the public bus from Frassineto to Meltina.