This title offers more than 100 papers originating in 20 countries, covering research on a widening range of methods for recharge enhancement and groundwater quality protection and improvement. These include: bank filtration; aquifer storage and recovery; and soil aquifer treatment, as well as rainwater harvesting and pond infiltration.  The emphasis is on understanding subsurface process to improve siting, design and operation and to facilitate use of stormwater and reclaimed water, particularly in water-scarce areas.