How to Survive Without a Visible Source of Water
Conserve any water you do have by avoiding exertion, rest in a shady spot when it is hot and try to keep cool. If you are sweating, your body is losing water. Try to eat less food as it takes more of the bodies fluids to digest food. Avoiding talking and breathing through your mouth. Most of all don't drink alcohol as it will dehydrate you. Be careful of drinking dirty or contaminated water as it can cause diarrhea or vomiting which will cause further dehydration.
Sterilize all water found by distilling or boiling which will take out all bacteria and make it safe. If you don't have a filtered water bottle along like the Lifesaver 4000 than using one of these methods is your best bet for safe water.
Best places to find water are areas where water would naturally drain if there was a rain storm. Water always likes to seek the lowest point so look at the bottom of gullies and dry stream beds. Water in the summer time often will be just under the surface of dry riverbeds or creeks. Dig down and see it the soil is damp. Look for lush vegetation as often there may be a small spring coming out of the side of a cliff or ground.
Look for or keep a plastic trash bag in your backpack as you can collect water from dew or rain. Set up your plastic to create a funnel to run it off into a water bottle or cup. You can even walk trough wet grass or other vegetation and wring out your clothes to get water. Salt water can be boiled and drinking water can be distilled. Be sure to have some tubing in your pack as this will be required to build a still. Keep salt with you as the body will naturally lose salt through urine and sweat. If you are experiencing dizziness, tiredness or muscle cramps this can be a sign you are salt deficient.
Building a solar still is easy and one of the best ways to guarantee a clean and pure source of water. Begin by digging a small hole with a diameter of about 3 feet and 18" deep. Take a piece of plastic trash bag and use a stone to roughen the underneath part to make sure the water droplets will run down to the bottom. Put it over the hole so it funnels down and is indented in the middle. Hold it in place with large rocks so it can't slip. At the very center place a small rock to hold it down in the hole. Underneath this plastic inside the hole you want to place a small cup or anything else that will hold water. When the sun comes up and warms the earth, water vapor will condense under the plastic and run down to the lowest point and drip into the cup. If you have dirty water or salt water, you can use this method distill water into pure drinking water even without a visible source of water.