AgriMAR Bangladesh

In large parts of Bangladesh’s rural coastal region the population has limited access to safe drinking water due to salinity in both shallow and deep groundwater. During the dry season, many of the delta’s rivers and canals turn saline. The abundant monsoon rains provide large amounts of freshwater and applying ASR has proven to be a suitable solution for bridging the water availability-demand gap: available freshwater from the rainy season can be stored in brackish aquifers to be used during the dry season. The rainwater is captured in ponds, filtered, and pumped into a surface reservoir from where it can infiltrate into the aquifer via one or multiple recharge wells. The water is stored in the underground, safe from contamination and evaporation. During the dry season, when the demand is high, it can be pumped to the surface.

Together with Dhaka University, UNICEF, and the Department for Public Health Engineering (DPHE) Acacia Water designed and piloted a MAR system for the provision of drinking water to rural communities in 2009. In several stages 95 MAR systems had been implemented by 2017, with the design being optimized throughout the project. Infiltration water is collected in a pond, pre-filtered in a sand filter and infiltrated in the shallow confined sand aquifer via four to six infiltration wells that are placed around a central abstraction well. The drinking water MAR systems have provided important knowledge on the technical functioning and – more importantly – on the socio-economic sustainability of MAR systems in the coastal zone of Bangladesh. It became apparent that operation and maintenance of the systems require considerable resources that make a robust financing scheme necessary. Upscaling of the technology, dissemination of knowledge, and general oversight should lie in the hands of a governmental body.

Drawing on the experience of implementing the drinking water MAR systems, the concept was adapted for irrigation water. In 2017, Acacia Water was approached by the Netherlands-based organization Saline Farming, partnering with the Bangladeshi seed company Lal Teer, to design a sustainable system for providing freshwater at a pilot site for salt-tolerant crops. The project is funded by the Dutch Postcode Lottery with the Dutch NGO ICCO as lead partner and is implemented by Acacia Water together with Dhaka University.

At the pilot site, rainwater is collected in shallow ponds. The developed AgriMAR system features a horizontal drain that is installed parallel to a pond over a length of 50 ft. For filtration, water flows from the pond to the horizontal drain through a jute-lined chamber with filter sand that can be removed for cleaning. The infiltrated freshwater displaces the brackish groundwater and forms a lens at the top of the aquifer. EC values of the ambient groundwater of 6.7 mS/cm and 12.2 mS/cm were measured in the shallow and deep filter respectively. As a considerable amount of infiltrated freshwater is lost to mixing at the boundary of the lens, only the shallow filter is used for recovery. The simple, low-cost AgriMAR system was constructed with locally available materials and unskilled labour (with the exception of the borehole which was drilled by a local contractor using a low-tech straight-flush manual rotary drilling technique). At the pilot site the recovered freshwater is mixed with brackish surface water to irrigate salt tolerant crops with water of constant low salinity. The AgriMAR system shows great potential for improving off-season irrigation agriculture in Bangladesh by allowing for an extra harvest of high-value crops during the dry season.

For more information on the project, contact our colleague Tine te Winkel (mailto:Tine.tewinkel@acaciawater.com) or read the brochure: