If you had been running your A/C, and the leak was coming from the back of the engine compartment on the right side, and the water was clear. Then the problem could possibly be nothing more than condensation running off of your A/C condenser coil mounted inside your car under the dash. It normally has a drain hose exiting from the bottom of you firewall outside your car. If you haven't been running your A/C, then check your coolant lines and possibly your heater core. If this leak was from the back toward the rear wheels, then check your brake lines for wear and tear. Steel lines rust out, and can fail at the worst possible times. And rubber brake hoses deteriorate as well, and are cheaper, and easier, to replace than the steel lines.