Dehydration

I am not sure why, but I got dehydrated today. While I did some yard work this afternoon, I drank plenty of fluids. At 6 p.m. this evening, I did a 3-mile road run and got dizzy afterwards. Later, I started losing vision. After drinking a lot of water, I feel okay. Guess I need to start drinking more water before and after and taking some electrolyte capsules.