You have to determine the source of the leak then decide on how to fix it.
water pump
Typically that leak is caused by a leak in the heating system. The heater core is under the dashboard, just above the passenger side.
This probably means that your heater core has sprung a leak ; you will probably find the passenger side damp form the leak itself - check with your mechanic .
You will need to replace the heater core.
Most likely a leak in the heater core, should be on the passenger side under the dash.
cap is off
heatercore leaking! also change thermastat.
You would have a leak, from either the pipes to the heater matrix (radiator), or the matrix itself.
The car will over heat.
check your blower motor, located under the dash board. its on the passenger side. if the leak is on the drivers side, i have no clue. but my hubby's car is leaking water from the blower motor on the passenger side. found out at the car wash...
there might be a leak some where in a coolant line. or maybe you have a leak in your radiator.
Check for a line leak to your heater core or a leak in the heater core it self. Usually it is under the dash on passinger side.