April 22, 1965 438+04
By Russell Stiklow
Climate change, groundwater, sustainable agriculture, water storage
Groundwater can be said to be the most important aspect of our collective water security in 2 1 century. When the rainy season comes, or the ground water supply is insufficient, farmers regard it as a water insurance policy. But we take this for granted, partly because-historically-until recently, the groundwater under our feet was basically invisible.
With the emergence of satellite-based remote sensing technology, we are now more and more aware that this vital water resource is in serious danger, and in many parts of the world, the speed of pumping water far exceeds the speed of its replenishment. In order to improve our adaptability to the changing climate and prolong our growing season, we must seriously consider not only pumping groundwater to the surface as we have always done, but also storing today's surface water underground to ensure our water safety tomorrow.
An empty groundwater recharge pool outside Tucson, Arizona, USA.
Photo: Bill Morrow on Flickr
It is an intervention measure that has been discussed for a long time but rarely implemented, which may be of great help to enhance the elasticity of water supply in arid and semi-arid areas-groundwater storage.
How does it work?
Groundwater storage-also known as managed aquifer recharge-is a process of purposefully reinjecting surface water into aquifers in order to manage water supply more effectively. This can be achieved by directly injecting surface water into the aquifer through the well, or by filling the recharge pool (as shown in the above figure) to make the surface water slowly penetrate into the groundwater level.
In Arizona, southwestern United States, aquifer recharge has become an important tool to combat long-term water shortage. For example, in 2006, the Tonopa Desert Recharge Project in this state began to operate, with the goal of storing water10.85 billion cubic meters per year. Using the 19 recharge basin distributed on 83 hectares of land, the project allows surface water to slowly refill the aquifer below, and the progress is measured by monitoring wells.
In three years, the operation successfully stored 600 million cubic meters of water underground, exceeding expectations, and improved the water security in this area. When surface irrigation or municipal water needs water again, wells and pipelines are used to extract supplementary groundwater as needed. These supplies can be transferred to other parts of the area through nearby canals.
Pilot studies are currently exploring the applicability of groundwater storage in other drought-prone areas of the world. Up to now, experts and development practitioners believe that this technology has the potential to be popularized on a large scale in many areas, although the effectiveness of underground storage varies with soil composition and aquifer types in specific areas.
For Karen Wilholt, an expert in groundwater management at IWMI in South Africa, groundwater storage "can play an important role in semi-arid and arid areas of Africa, such as Botswana and South Africa, where it rains occasionally and the options for surface water storage and transfer have been exhausted."
At the same time, many research plans and pilot projects are also expanding the scope of underground storage technology and exploring its potential applicability in small island countries such as India, the United States, Thailand, Australia, Central Asia and even Maldives.
"In principle, in many geological environments, it is possible to increase the underground water storage capacity," said Vladimir Smakhtin, the project leader of IWMI on water availability and access. "The degree will of course be different."
Climate change and the need for better water storage
With climate change making seasonal precipitation and surface water flow more and more unstable, the need for improved storage technology is more urgent than ever. Experts agree that storing water underground is far more effective than storing it in surface reservoirs. This is because storing water underground can minimize evaporation, which is the main reason for water loss in surface reservoirs in arid and semi-arid climates.
Underground storage can adapt to greater changes in farmers' needs, especially in drought or dry season, when irrigation water may be most needed. Paul Pavelic, a hydrogeologist and groundwater expert at IWMI, said: "By helping to better match the availability and demand of water, it can greatly help to improve the water use efficiency in rain-fed and irrigated areas."
Pavelic said that by making groundwater available "where and when it is needed", replenishing the aquifer with rainwater in rainy season provides "protection against climate change", thus enhancing water security, so rural livelihoods will be improved in dry season. The surface water and groundwater expert from IWMI Laos office added that by providing additional groundwater for irrigation, the replenished aquifer means that "farmers can increase the number of planting seasons".
What other policy measures or infrastructure investment can be combined with underground storage to make more effective use of groundwater in a sustainable way and improve our climate flexibility?
Does this count?