On average, there is about 31 inches of precipitation per year. This leaves 12 inches that can be used for ecological purposes and sustain the human population's water needs. Of this, 6.2 bgd is taken in by plants and evaporates. This leaves 6.2 bgd available to flow into streams and rivers, to seep into ground water, and to retard salt water from moving into estuaries and aquifers. Mr. Kecskes described the impact of human activities.
Human activities can lead to nondepletive or depletive water use.
One municipality where nondepletive use occurs is Trenton. Water that has been used is cleaned by sewage utilities and then is restored to the system because it is discharged to rivers and streams. Ocean County' s use is depletive because it takes the water that has been used and cleaned and discharges it into the ocean. The water is no longer available to the system. The water taken out is ground water that would otherwise go into streams and rivers.