Nicol-André Berdellé of TS Prototype Creation on a new rainwater management solution for arid regions, which reactivates dry wells for use as cisterns and Aquifer Storage & Recovery units (ASR)
Falling groundwater tables are a worldwide phenomenon, an invisible ebbing of the most elementary fossil resource we use. While the economy is dependent on hydrocarbons that feed its huge energy needs, life in essence depends on water. Plummeting groundwater resources are more than a challenge to the economy, the financial system or high standard of living. They represent the foundation of our achievements, with deep implications on the future of civilisation.
Once a working system of food provisioning becomes established and effective in a civilisation, the additional branches of its economy starts developing. But as fossil water-based agriculture dies down, the Arab region could be looking at a future scenario which makes energy crisis a trivial topic.
Despite the blue revolution, overall water demand is increasing much more rapidly than what all water conservation, re-use and desalination efforts can make up for. Water tables are still falling in the Middle East at the rate of several metres every year.
However, there is a potent and deployable solution, which can stop and even reverse the trend of falling ground water levels. In between rainwater management and aquifer recharge, this option utilises existing wells that have run dry. It was originally designed by TS Prototype Creation as a developmental aid project for Niger, as an engineering challenge to create the most cost-effective solution for rainwater management possible by reactivating dry wells as cisterns and Aquifer Storage & Recovery units (ASR). It relies in the fact that traditional wells at the bottom of watersheds can be filled without any need for pumping. The entire area around the well could be modified and serve as a funnel to collect the short but intense rainfalls that occur in the Middle East, with drainage ditches speeding up the flow.
Simple structures on the surface slow down water and keep back surface sediments, thus helping collect clean water. The excess water is drawn from top of the filled cistern well and introduced back into the natural aquifer. This solution works well because the geological aquifer, in most cases, will lead the water back to the bottom of the well. If the water was introduced from anywhere else, the chances are that it will vanish in subterranean canals.
This solution is a self-sufficient and sustainable reclamation utility, and does not require significant maintenance. It could be compared to a palm oasis because a large surface area receives a rainwater management system, the difference being that water is stored securely underground and the system is fully up and operational from the first rain event on. Furthermore, the Recharge Well (RW) shows a positive Material-Input Per-Service-Unit (MIPS). The RW is not a quick profit solution; it is a stable process to recreate Life Support Systems (LSS). This is the foundation of our economy and a pre-requisite for financial profit.
Injection wells aren’t new, but retrofitting and activating a barren, open well, utilising it as a cistern and filtrating the runoff water for aquifer recharge is. Even the practise of recharging aquifers is hardly found anywhere in the world, barring a few examples being implemented in Bangalore and a strategic water reserve being built in Abu Dhabi.
Injection wells are also used to deposit treated wastewater or hazardous effluent from factories. The US Environmental Protection Agency (EPA) classifies injection wells into five groups, depending on the type of waste to be disposed in them. The same is reproduced below as follows:
- Class 1: Receives industrial, commercial, or municipal waste fluids injected beneath the lowermost formation containing an underground source of drinking water (USDW) within 1/4 mile of where the well was drilled. Class 1 wells are prohibited in Washington State.
- Class 2: Receives fluids that are brought to the surface as part of oil or natural gas exploration, recovery or production.
- Class 3: Used for mineral extraction. 2 basic types: solution mining and in-situ leaching for minerals. Class 3 wells are prohibited in Washington State.
- Class 4: Receives radioactive or hazardous waste injected into or above underground sources of drinking water. Class 4 wells are prohibited in WA State except for Class IV wells used at an approved Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) or Resource Conservation and Recovery Act (RCRA) facility that re-injects treated ground water into the same formation.
- Class 5: All other injection practices not included in the other classes. Class 5 injection wells, the most common injection well in our state, are generally shallow wells used to discharge fluids into or above a ground water aquifer. In many cases, these aquifers are shallow, unconfined or surficial. Large on-site septic systems, serving 20 people or more per day or having a capacity of 3,500 gallons per day, are considered Class 5 wells.
The wider neighbourhood of RW hosts various practices and techniques of groundwater or aquifer recharge through surface percolation or injection . At the seventh International Symposium on Managed Aquifer Recharge in Abu Dhabi last year, the main topic was the costly injection technology. In contrast, the unique advantage of RWs is not recharging or storage but as an option of harvesting huge amounts of rain, otherwise lost. A major difference between recharge by percolation and RWs is the amount of evaporation on the water surface, which is dramatically higher if the rainwater is not directed underground.
Another difference is the quality of water. RWs provide clean drinking water in the cistern after the rain event. Only after the well shaft is full, the excess water will percolate into the aquifer at the sides. Recharge Wells are about drinking water, the most important type of water. The quantity and quality of water in a Recharge Well is layered out for highest security and purity in drinking water utilities.
To cover the drinking water demand for one person for one year in an arid desert environment, a rainwater catchment area of only 14m² suffices (with an annual precipitation of 100-110mm in Riyadh and four litres per day).
The success of RWs rests on finding the right method of converting the desert surface into a funnel to collect the rainwater, in combination with the right location and subsequent resettlement efforts to maintain the unit.
So far, I have discussed reactivating dry wells. The situation in the (new) urban areas close to the Hajar Mountains, with lots of sealed surface, is different. In these areas, new Recharge Wells built in the exact same manner reach payback quicker and with less maintenance, and they could even help in solving the problem of flooding. The Musandam peninsula could receive more rain in the future due to climate change, and it would be a measure of foresight if these simple measures are implemented towards this prospect.
The problem with ASR is that it is been developed by scientists or specialists who want to apply all available data and formulas, engineer hydro geological models and get paid for the most costly planning process possible. But the models frequently turn out to be wrong, particularly in the natural sciences, were models are based on countless assumptions and results are erratically different due to plenty of levers in the calculation and some personal choices.
Understanding climate or geology will always be a partial matter and cannot be controlled like steel-alloys in mechanical engineering or structural analysis. This is a truth that always eludes the investor. The transposition of our trust in technology on to natural sciences could turn out as one of the momentous errors of our time. Probably the best example in modern history has just occurred in Japan: Engineers simply took wrong assumptions about geological events, although they were otherwise fully qualified and able to built a highly complex machines and operate them successfully over a longer period of time.
Another downside of industrial ASR solutions is the ratio of investment to recharged water unit, or retrievable water unit. This ratio can never be as good as recharge into a formerly operational well and its attached, proven aquifer. On top of that RWs can be operated without any machinery, fossil energy, water or lubricants.
The strategic reserve in Abu Dhabi was contracted to be built for $430 million, one cubic meter of the injected water costing $26 only counting the construction. RWs cost seven orders of magnitude less. And like ASR, the amount of water that can be stored through the RW is principally limitless. Both technologies are simply access methods to the vast underground reservoirs that are probably interconnected, throughout vast portions of Arabia, as per studies. In both cases, there are question marks on the issue of recovery, but only the cisterns of RWs are exempt from these insecurities.
The lifespan prospect of a delicate ASR, which is crucially dependent on a certain company to operate it, looks very dim compared to an RW which will be passed on from generation to generation, empowering people to be self-reliant and reclaim their land step by step.
1. Percolating young minds: Case study of recharge wells dug by an educational institute by Shree Padre Dec, 2007
2. The Groundwater Recharge Movement in India, by RAMASWAMY SAKTHIVADIVE
(The author is start-up manager of TS Prototype-Creation. He may be contacted at trueschool (at) fastmail.fm; www.prototype-creation.de)