SWS provide innovative, practical concepts for advanced freshwater management. SWS are distinct from conventional technical approaches as SWS provide a coupled solution of a natural ecosystem (service) with a technological approach that allows for an enhanced protection and utilization of the freshwater resources in coastal areas. SWS are flexible and adaptive to the environment and changing socio-economic requirements. SWS build on novel well designs and configurations, and sophisticated ICT controlled water management based on enhanced groundwater monitoring and modeling. SWS have been tested in field scale pilots and are near-market ready (Technology Readiness Level 7-8). SWS can be applied at a range of scales, from the agricultural field to the scale of small watersheds, to water well fields of large cities. Typical applications of SWS are:
Freshkeeper, dual zone abstraction against water well salinization. Fresh and brackish groundwater are pumped simultaneously from different depths, providing control over the position of the fresh-brackish interface. The pumped brackish water may serve as an additional water source for high added value freshwater applications after desalination.
Freshmaker, enlarging, protecting and utilizing freshwater lenses with horizontal wells. This technique was initiated by the recent development of horizontal directional drilled wells (HDDWs). HDDWs enable abstraction of deeper saltwater below the freshwater lens over a long transect, while a second, shallow HDDW allows for infiltration and abstraction of large freshwater volumes.
ASR-coastal, temporal storage of freshwater in brackish groundwater. Standard aquifer storage and recovery(ASR) approaches are unsuitable in brackish groundwater environments. ASR-coastal uses multiple partially penetrating wells to enable deep injection and shallow recovery of freshwater, which demonstrated a boost in freshwater recovery from less than 20% to more than 60% of the injected freshwater.
These first SWS applications have all been developed within public-private partnerships of innovators in the water market and they are starting to gain the interest from the market’s early adopters. Freshkeeper has been successfully piloted in a well field that was abandoned in 1993 because of salinization. Water company Vitens now sees opportunities to reopen this well field by applying the Freshkeeper at full scale. A recent feasibility study has shown the potentials of Freshkeeper to abate salinization problems in Florida, USA, and to guarantee the long-term drinking water supply there. ASR-Coastal has been successfully piloted in two greenhouse areas, supplying the horticulture farmers with sufficient water to overcome the dry summer months. Local authorities now consider ASR-Coastal as an important tool serving their regional water governance, increasing the self-supportiveness of greenhouse farmers. Freshmaker is being piloted at an orchard in southwest Netherlands, and has supplied the farmer with additional irrigation water during two consecutive summers already. Recently, his peers in the region have shown interest in the technique and have inquired for a Freshmaker feasibility study.
Despite this growing interest from early adopters, market uptake of SWS is hindered by a number of barriers, including a lack of real-scale demonstration of long term viability, a lack of knowledge of new technologies, and a lack of capabilities upon making investment decisions. Our ambition is to break these innovation barriers and to open the market for subsurface water technologies in coastal areas worldwide.