When it rains I often hang something from the edge of my tarp to tighten it up and stop water pooling in the fabric.
Providing your tarp is kept reasonably clean, this rainwater can be used for cooking, washing or even drinking if treated properly.
Often what I do is hang a “Millbank” bag on the tarp with a drip line to carry the water into the bag instead of just over the edge.
This little project is for direct collection into a metal bottle and is very easy to make.
It started out as a spare lid from an old aluminium bottle that had seen better days, a small pudding basin, aluminium in this case, and a short length of tubing.
The lid has a loop in it that makes hanging the collector easy and a bit of nylon cord finishes the list.