Mark Tonkin : dRHS Irrigation System

  • United Kingdom

Subsurface Vapor Transfer Irrigation

A subsurface irrigation technology that enables agriculture to use water efficiently and also make use of brackish or saline water without the need for either expensive purification, desalination, fine filtering or pressurizing.

Two billion people worldwide experience intermittent food insecurity and 1.1 billion lack clean drinking water. At the same time, changing weather patterns, desertification, over-irrigation, and over-farming are resulting in diminished arable land, less available clean water, and reduced agricultural productivity in some parts of the world. DTI-r has a subsurface irrigation technology that enables agriculture to use water efficiently and also make use of brackish or saline water without the need for either expensive purification, desalination, fine filtering or pressurizing.


Of the 332 million cubic miles of liquid water on Earth, over 97.5 percent is unsuitable for agriculture due to high salinity. Because irrigation with untreated saltwater can result in plant dehydration, poor growth, and eventually death due to salt poisoning, there are vast land areas around the world that are non-productive because the only available ground or surface water is high in salt. The ability of farmers to use saltwater to grow their crops could help alleviate current and future food scarcity problems, as well as improve the availability and efficient distribution of limited freshwater resources.


The dRHS™ irrigation technology provides an opportunity for land that currently cannot be cultivated due to scarcity of clean water to be brought into productive use using little or no-value water. Developed by DTI-r, this innovation utilizes a network of subsurface pipes that can be filled with almost any type of unpurified water—brackish, salted, polluted, industrial wastewater, agricultural run-off. The pipes are lined with a unique hydrophilic DuPont material that allows water vapor—which cannot carry salts—to diffuse through the pipe walls, while the contaminants are retained within the pipes. This process, known as pervaporation, is a combination of membrane permeation and evaporation. It works at ambient temperature and pressure, and is controlled by the humidity gradient between the inside and outside of the pipe.

“Pervaporation is a well-known phenomenon, but it hasn’t been applied to this type of application before. In most cases, pervaporation is used with hydrophilic membranes to remove water from a chemical of interest. The water is discarded and the substance remains. We’ve completely turned this concept it on its head. The part we want to use—the clean water—pervaporates out, and the part that we don’t want—the salt—stays in the pipe”  – Mark Tonkin, Design Technology & Innovation (dTI-r)
Plants take more water from the pipes as the soil dries out, less if the surrounding soil becomes wetter. As a result, plants do not become over watered and there is virtually no loss to evaporation or run-off. Unlike more traditional irrigation systems, the dRHS™ requires very little in the way of infrastructure and consequently very little in the way of maintenance and operations costs.


The ability of farmers to grow crops on previously non-arable land, and in a manner that uses little to no scarce freshwater has the potential to transform food production, increase water availability, reduce polluted run-off, improve soil quality, halt desertification, and address climate change issues. In addition, the ability of impoverished people to grow their own food could reduce their dependence on imports, gain economic independence, and improve their own health and well-being.

“We want lots of pipe in the ground. We see this as something that can do a huge amount of good for a lot of people in lots of places around the world. It means that people who currently need to scratch a living can grow their own food using whatever dirty water they’ve got. This system is completely different from everything else that exists today” – Mark Tonkin, Design Technology & Innovation (dTI-r)
DTI-r has an active program to test the dRHS™ in both lab and field settings. However, DTI-r is a small company and currently almost everything it does has to be linear. The next step is to develop the ability to scale up and pursue multiple opportunities simultaneously in order to reach more people, reduce costs, and further challenge the capabilities of the system. The more diverse the trialing and the more experience that can be gained with the technology, the faster the benefits can be honed to focus the product rollout where it will be best applied and most valued by the users.