Start of Westland pilot
Fresh water lenses in saline groundwater
Michiel van Haersma Buma, chairman of the Water Buffer Foundation, starts up the aquifer storage and recovery installation at the tomato grower Prominent in ’s-Gravenzande. In attendance are numerous representatives of the horticultural sector, the business community and the water sector. The installation is part of a pilot involving KWR, B-E De Lier and Prominent, and is partly financed by the Knowledge for Climate research programme and by the Horticultural Product Board. “The research contributes to enlargement of the possibilities to use the salty subsurface for the storage and recovery of fresh water,” says KWR researcher Marcel Paalman.
The permanent availability of good quality irrigation water is essential for the operational continuity of greenhouse horticulturalists. Rain-water is the sector’s main source of irrigation water. The water is collected in surface basins and then used as irrigation water in the greenhouses. The problem is that in the summer the demand for water exceeds its supply. The greenhouse horticultural companies in Westland therefore commonly use brackish/saline groundwater, which first has to be desalinated, as their alternative water source. Another supplementary option is to make use of the autumn and winter precipitation surplus by storing it temporarily underground.
Fresh water is stored in a brackish groundwater system
Fresh water lenses increase fresh water available for horticulturalists
By resorting to underground storage, the horticulturalists can enlarge their fresh water storage capacity without occupying any extra surface space. The technique of using the subsurface to store and then recover water has long been used and is known as Aquifer Storage and Recovery (ASR). What is new about this pilot is that the storage takes place in a brackish/saline groundwater system. An important research question is then how to create a viable fresh water lens that produces good quality water. A small-scale pilot at a grower’s in Nootdorp earlier produced good results. Now the technique is being applied in a greenhouse area covering 27 hectares, where water is being collected and injected at different depths in an aquifer sand layer.
New research into supplementary techniques and sources
Over the course of the year, researchers Koen Zuurbier and Marcel Paalman carefully monitor the pilot’s results. Zuurbier regularly posts reports on his weblog. There is a lot of precipitation in the autumn of 2013. As a result, in early 2014, 65,000 m3 of fresh water is injected in the aquifer. Because the tomato growers need even more water, Zuurbier and Paalman also look into the possibilities of using reverse osmosis to desalinate rain-water that is mixed with saline groundwater. This research is conducted within the framework of the European project DESSIN. They are also examining whether a connection can be made with research into effluent reuse (Delft Blue Water, part of TKI Water Technology), and in this way increase the volume of the fresh water lens.
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Senior scientific researcher