I've gotten water in bags from trickles. If it's moving but hard to get the bag on, throw your spoon in there so the handle cantilevers out. The water will run down the handle and give you a spot to fill up the bag from. Slower than a pump but it works.So next question, areas with limited water sources and or tiny streams of water, how do the bags work? All I've ever have used have been pumps, weight isn't a problem for me, all I care about is the safest drinking water.