Managed Aquifer Recharge for Irrigation in Saline Environments

Water for agriculture
Bangladesh

Agriculture in the coastal plains of Bangladesh faces serious challenges from seawater intrusion. During dry season, ponded monsoon rainwater is insufficient to sustain irrigation throughout the crop cycle, while near-coastal surface water becomes unsuitable for irrigation due to salinity intrusion. Farmers of rainfed crops are therefore limited to just 1 or 2 harvests per year. Managed Aquifer Recharge for Agriculture (AgriMAR) offers a low-key low-cost method to store freshwater underground for later use. Economic assessments show profitable business cases for bitter gourd and watermelon with the AgriMAR system.

Manual drilling of the injection and recovery well of the AgriMAR system.

Key Takeaways

  • Storing seasonally abundant freshwater from rivers and monsoon rains underground protects it from salinization, evaporation, and contamination, ensuring availability during the dry season for irrigation.
  • AgriMAR provides the additional freshwater needed to stabilize fluctuating salinity levels in coastal rivers, ensuring reliable irrigation for salt-tolerant crops during germination and throughout the dry season, enabling higher yields and more resilient crop production.
  • AgriMAR enables farmers to grow high-value crops such as watermelon and bitter gourd in the dry season, adding additional harvests and improving climate resilience.
  • Positive benefit-cost ratios demonstrate potential for higher farmer incomes: 1.13 for bitter gourd and 1.97 for watermelon, with watermelon being particularly profitable due to higher yields and lower input costs.
  • AgriMAR is a low-energy, low-tech system built with locally available materials and labor, making it affordable, easy to maintain, and adaptable for widespread use under local ownership.

Project Details

Started: 2018 – Completed: 2019
Ref: 170752 | Status: Completed
Project title: The Salt Solution Project – piloting and business case development of AgriMAR

Background

The AgriMAR Bangladesh project was initiated to address the worsening water scarcity and salinity challenges in the country’s coastal plains. In these areas, seawater intrusion and brackish surface water make irrigation nearly impossible during the dry season, leaving farmers restricted to one or two rainfed harvests per year, usually rice during the monsoon season.

Meanwhile, climate change is intensifying the problem through sea-level rise, erratic rainfall, and soil salinization, threatening food security and livelihoods. To break this cycle, AgriMAR introduces a low-cost, climate-smart solution: storing abundant monsoon rainwater and seasonally available fresh surface water underground through Managed Aquifer Recharge (MAR), enabling safe recovery for irrigation when needed.

This approach creates opportunities for off-season cultivation of high-value crops, strengthening resilience to climate shocks, and supports sustainable agricultural development in one of Bangladesh’s most vulnerable regions.

Activities

The MAR system was designed and piloted as MAR scheme adapted specifically for irrigation. The design drew on lessons learned from 95 MAR systems developed for drinking water under a previous MAR project in Bangladesh for UNICEF.

A saline test location was selected, and a recharge system was built where monsoon rainwater and seasonally abundant fresh surface water was collected in shallow ponds, filtered through a jute-lined sand filter, and infiltrated into a confined aquifer via recharge wells. This stored freshwater displaced brackish groundwater, forming a usable freshwater lens.

The AgriMAR system was developed with low-energy, low-tech designs by selecting and adapting locally available materials and mobilizing local labor, ensuring community ownership and long-term sustainability.

Irrigation trials with salt-tolerant crops were conducted. The recovered freshwater was used to irrigate crops, sometimes blended with brackish surface water to reach optimal salinity levels. The trials demonstrated that off-season cultivation was feasible, creating opportunities for higher farmer incomes.

Groundwater quality and system performance were closely monitored with piezometers to track groundwater levels, changes in salinity and recovery efficiency.

Farmers, local stakeholders, Dhaka University, and international partners collaborated in design, implementation, and training.

Findings

The project demonstrated that storing freshwater underground for dry-season irrigation is technically feasible, economically viable, and environmentally sustainable in the coastal regions of Bangladesh.

The AgriMAR system infiltrated about 5,400 m³ (190,000 ft³) of freshwater annually, with a recovery efficiency of ~ 50%, an improvement over the recovery efficiency (~33%) of earlier drinking water MAR systems in similar conditions.

The recovered freshwater enabled off-season irrigation of high-value crops such. Mixing recovered freshwater and brackish surface water provided irrigation water of constant salinity, suitable for salt-tolerant crops.

Cost-benefit analyses showed a positive business case:

  • Watermelon: Benefit-cost ratio of 1.97, with net returns of ~ €1,527/year.
  • Bitter gourd: Benefit-cost ratio of 1.13, with net returns of ~ €221/year.

Watermelon proved most profitable due to higher yields and lower input costs. However, growing demand for bitter gourd, both nationally and internationally, may improve its profitability.

AgriMAR can mitigate salinization impacts, which are projected to reduce rice, and wheat yields by 8% and 32% respectively by 2050 in Bangladesh’s coastal areas.

Low-cost design using local materials and unskilled labor proved practical and scalable, making the system accessible for rural settings. Farmers indicated willingness to invest 12–20% of turnover in irrigation water, but access to affordable financing (loans, grants, or subsidies) remains a barrier. Therefore, upscaling requires strategic partnerships with seed companies, government agencies, and microfinance institutions.

Project Areas

The project was implemented in Bagerhat District, in the coastal plain south of Khulna. This region lies within the vast Ganges–Brahmaputra–Meghna delta, an area that is highly fertile but extremely vulnerable to salinization and climate change impacts. During the dry season, most of the rivers and canals in the delta become brackish or saline, making the water unsuitable for irrigation or drinking.

The pilot site, Rampal Agri Farm, lies in a saline zone where electrical conductivity (EC) of groundwater ranges between 6–12 mS/cm, indicating brackish conditions. The aquifer consists mainly of fine sands, suitable for infiltration and storage of water. Annual rainfall averages 1,900 mm, concentrated in the monsoon (June–October), providing abundant freshwater otherwise lost to runoff and evaporation.

This geographic setting illustrates both the challenge and the opportunity for the AgriMAR project: while seawater intrusion and soil salinity undermine agricultural productivity, heavy monsoon rains provide a renewable freshwater source that can be safely stored underground for climate-resilient irrigation.

Geographic scope: Local

Downloads and Links

AgriMAR Bangladesh Project Overview ‘Managed Aquifer Recharge to Provide Irrigation Water for Agriculture in a Saline Environment’ (2019).

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AgriMAR Bangladesh Technical Report ‘Agricultural Managed Aquifer Recharge to Provide Irrigation Water for Saline Agriculture in Bagerhat District, Bangladesh’ (2019).

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In Cooperation With

Commissioned by:

Salt Farm Texel

Funded by:

International Cocoa Organization (ICCO)

Project partners:

Salt Farm Texel Lal Teer Acacia Water Dhaka University Department for Public Health Engineering (DPHE)

Contact

Harmen van den Berg

Hydrogeologist

+31 6 11 45 35 87
harmen.vandenberg@acaciawater.com
harmenvandenberg1

Related topics:

Borehole drilling, Climate resilience, MAR, Managed aquifer recharge, Salinization, Underground water storage, Water harvesting

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