"Store drinking water for circumstances in which the water supply may be polluted or disrupted. If water comes directly from a good, pretreated source then no additional purification is needed; otherwise, pretreat water before use. Store water in sturdy, leak-proof, breakage-resistant containers. Consider using plastic bottles commonly used for juices and soda. Keep water containers away from heat sources and direct sunlight."
Depending upon your circumstances, you may or may not be able to collect water using these emergency methods. Having water already stored is a sure bet. If you want to plan on utilizing these alternate methods, great! But I would recommend that you get your basic water storage first.