STOCK RESOURCES VERSUS FLOW RESOURCES

Stock resources are resources that can be permanently expended, and are therefore non-renewable, and whose quantity is usually expressed in absolute amounts rather than in rates. Examples are coal and petroleum deposits. Flow resources are not permanently expendable, i.e., they are renewable, under usual circumstances; they are resources that are replaced. They are commonly expressed in annual rates at which they are regenerated. Examples are fresh-water runoff and timber.