An innovative seawater irrigation system without filtration or desalination for agriculture and gardening

The planet is facing an unprecedented water crisis: 98% of available water is saline (only 2% is fresh), and 70% of that is used in agriculture. With the growing demand for food and the worsening effects of climate change, the agricultural sector is facing a major challenge. According to forecasts, by 2025 two-thirds of the world’s population will suffer from water scarcity. In this context, it is urgent to innovate in efficient and sustainable irrigation systems that reduce dependence on fresh water and take advantage of abundant resources such as seawater.

In this context, the Agua de mar project has emerged. It is an innovative system that allows irrigation with seawater without the need for filtration, desalination, or chemical treatment. The system is based on capillary irrigation (i.e., watering from below the soil), through the construction of a controlled artificial water table located beneath the ground. This structure supplies the upper substrate layers with the necessary moisture to maintain, for example, a garden of ornamental plants in optimal condition.

This structure mimics the behavior of a natural water table, which is a subterranean water reserve formed when rainwater or other sources infiltrate the ground and accumulate at depth.

To operate the system, a seawater intake point and a return point are needed. Seawater is extracted from the marine aquifer through the construction of a lined well. This greatly reduces the risk of clogging and high maintenance costs. The extracted seawater is channeled to the base of the garden or the artificial water table. The water flows from one end to the other, enabling constant renewal and avoiding the generation of brine (highly saline wastewater).

Using a natural filter in contact with the seawater and leveraging its capillary properties, water and moisture are delivered to the upper soil layers. This filter helps reduce seawater conductivity, thus preventing soil oversalinisation. Its most remarkable feature is its self-regeneration capacity. At any time, without altering the garden’s composition, the filter can be restored to its original state, removing all accumulated salts without losing its properties.

Impact

The system has been tested both in gardening and agriculture. As a pilot project, a garden at the Joan Maragall Center in Badalona has been in operation for six years. It is located about 650 meters from the shoreline. The saline water comes from a 25-meter-deep well, with strong marine intrusion and a concentration of about 24–26 grams of salt per liter.

In the agricultural field, tests have been carried out with crops such as potatoes, lettuce, cherry tomatoes, and especially chard. The trials have shown that irrigating with seawater can shorten crop cycles—as in the case of chard, which can be harvested in 28 days instead of 42—and that the resulting vegetables can have up to three times the nutritional content of those irrigated with fresh water. In some cases, a naturally more intense flavor has also been observed, as with cherry tomatoes.

Expert chefs from the Alícia Foundation have highly praised these qualities in cooking, confirming that this system can produce superfoods and be a realistic and sustainable alternative in times of drought, reducing reliance on fresh water and improving food quality.

Budget and Funding

The project, with a duration of nine years (2009–2017), is the result of a collaboration between the Aqua Maris Foundation, the CRESCA of the UPC, and the ISMET training center. It began with the installation of a pilot garden at the Foundation’s headquarters in Badalona; later, detailed trials and monitoring were conducted at CRESCA’s laboratories and greenhouses, culminating in the creation of Seawater Irrigation Systems, S.L.

To make this journey possible, a total investment of between € 500,000 and € 700,000 has been mobilised. This range includes, on the one hand, in-kind contributions from research staff and use of equipment at CRESCA-UPC; and on the other hand, direct costs and R&D activities covered by the Aqua Maris Foundation (construction and maintenance of pilot sites, acquisition of sensors and materials, periodic analyses, and technology transfer efforts).

The combination of public and private resources has enabled the achievement of TRL 6–7 in gardening and TRL 4 in agriculture, with a relatively modest investment—demonstrating the economic and environmental feasibility of the technology and paving the way for new funding to scale it commercially.