Decide what type of project you want to do. There are two basic types of science projects. Projects where you learn about a topic, summarize information and answer a question are sometimes called literature projects. Then there are experimental projects where you actually perform an experiment to test a theory you have. Experimental projects are usually more challenging at the elementary level but can also be fun. Even if you do an experimental project, you will still have to do some research to prepare for it and interpret your results.
Decide on a topic for your project. If you want to do a literature project, think of a question connected to drinking water that you would like to know the answer to. It might be something you have always wondered about, or it could be connected to the school curriculum. An example question might be "Where does the drinking water in our city come from?" For an experimental project, think of a theory or idea that you could test. For instance, "Which type of bottled water tastes best?"
Perform an Internet search looking for web sites connected to your topic. There are many sites dedicated to the topic of drinking water that you can use. Sources that provide a large amount of information are often those run by government agencies or international committees. Examples of appropriate resources are the United States Environmental Protection Agency (EPA), the World Health Organization (WHO), the Centers for Disease Control (CDC) and the World Water Council. The EPA has a resource called the Water Sourcebooks, which provide information and activity ideas for each grade level. Another source of research information is West Virginia University's National Environmental Services Center.
Take notes on the information you get from the websites you visit. Remember to note which site you used to get each piece of information. Try to concentrate on interesting facts and figures that people might not already know.
Put all the information together in a way that make sense, is easy to understand and answers your project question or helps you plan out your experiment.