This is extremely simple. Place a large, white, absorbant piece of paper under your car at night. If it is wet, that's a sign that your water pump may be leaking. It is definitely coolant if it is green.
What if my water pump is leaking?
With the engine turned off, open the hood of your vehicle. There is a pullet connected to the pump. If you find all of the belts in the vehicle, there is more than just one pulley. Other parts of the vehicle use a pulley to operate like the alternator and maybe the air conditioner. Power steering and a smog pump will also have pulleys. A mechanic can show you the right one.
When you find the right one, see if it's loose. Grabbing it from both ends, check if you can rock it back and forth. If the pulley does have play you will be hearing the bearing that is bad. A low pitch grinding when the engine is running will be that.
The water pump is situated in back of the pulley and you can look for a coolant leak. The pump may be working but may need something as simple as a gasket to prevent the leaking. Unless you just replaced it, you may want a new water pump. Other components: The heat of the summer means that your coolant system needs to be working optimally. Preform routine flushes of the radiator. The coolant in the vehicle was not intended to stay in there forever. Repairing damaged radiators is way more expensive than flushing it once a year.