During outdoor activities, water is a vital resource for survival. When your drinking water runs out and natural water sources are not safe to drink directly, you need to learn the following methods to filter water.
1. Sedimentation Method
After collecting the water you’ve found, you can add a small amount of alum or mashed kapok leaves, cactus, or walnut kernels, stir well, and let it settle for 30 minutes. This way, you’ll get relatively clean water.
2. Improving Saline-Alkaline Water
In the desert and Gobi areas of Northwest China, most of the water available is saline-alkaline and not drinkable. You can dig a sand pit with a diameter of 1.5 meters and a depth of 1 meter in areas with moist sand or brackish water, cover it with a layer of transparent plastic film, secure the edges with stones, and place a small stone in the center so that the plastic film forms an inverted cone. Make sure to place a water-catching container beneath the cone in advance. Sunlight passing through the plastic film causes the moisture in the sand pit to evaporate, and the water vapor condenses on the plastic film into water droplets, which then drip into the container from the tip of the cone. This method can yield about 1.5 liters of distilled fresh water per day.
3. Filtration Method
When the water source you find is muddy with floating debris, microorganisms, worms, or leech larvae, and the surrounding environment is unsuitable for digging a pit, you can use a high-quality, durable plastic bag. Poke small holes in the bottom, or use a cotton glove, handkerchief, sleeve, or pant leg. Alternatively, you can use a cola bottle—first remove the bottom, then poke several small holes in the cap. Next, fill it from the bottom up with 5 to 7 layers of clean fine sand, each layer 2–4 cm thick. Press the layers down firmly. Slowly pour the unclean water into this makeshift filter. Once filtered water begins to drip out from the bottom, you can collect the clean water using a basin or kettle.
4. Seawater Desalination Method
At the seaside, you can desalinate seawater by boiling it to collect distilled water. When boiling seawater, place a towel inside the lid of the pot to absorb the distilled water droplets, then wring the water into a large shell or other container. Repeat this process to obtain the desired amount of drinkable fresh water. In winter, you can also freeze seawater in a container—the resulting ice can be used as drinking water.
The above methods can help in emergencies, but they are not suitable for long-term consumption. Therefore, it’s best to bring enough drinking water when heading outdoors.
