"Reservoir is needed to meet with the deficit which occurs due to imbalance in the rate of influx and efflux."
Could you be please explain this sentence???

 "Reservoir is needed to meet with the deficit which occurs due to imbalance in the rate of influx and efflux." This means that we need a reservoir of the natural resources to maintain their concentration when the use of resource gets unbalanced. Example: Carbon cycle is the reservoir of carbon in nature which maintains its concentration in the environment similarly the various nitrogen reservoirs maintains its concentration in the encironment.