Drain less for more water

At present, the groundwater level is low to very low at 51% of the measurement points. Even in my nearly empty rainwater tank, I see we’re experiencing another dry spring. This is not good news for agriculture and nature in Flanders. In most places, plants here evaporate more water on an annual basis than it does precipitation. Thus, the cumulative deficit in precipitation increases systematically over the years in almost every location. Too much rainwater cannot replenish the groundwater supply. After all, it pretty much evaporates before it finds its way back underground. Moreover, we do not have many large rivers to provide fresh water. Therefore, groundwater is an important source of water for many users, including agriculture. But this source is now under pressure.

You may have already noticed: in Flanders there are canals and drainpipes everywhere. These ensure that groundwater that approaches the surface can flow away. Thus the drainage alters the movement of groundwater. On agricultural land, it must be ensured that the roots of our crops receive adequate oxygen. Drainage is also important for the cultivation of the land. After all, if agricultural machinery has to work on very wet soil, it destroys the soil. Thus, drainage changes not only the groundwater table, but also how plants grow and how much they produce.

All this drainage affects the water system in the surrounding landscape. This is because the canal and tube system slowly but surely moves water from wetter areas to larger streams and eventually to the sea. Existing large-scale Flemish groundwater models estimate that drainage discharge is between 10 and 30% of the groundwater supply. That water then disappears from the area rather than replenishing groundwater supplies or feeding natural rivers. This is also necessary when the weather is dry for a longer period. Since agricultural land occupies nearly half of the area of ​​Flanders, it is likely that significant gains could be made here by increasing groundwater recharge and thus water availability.

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It is not possible to simply stop draining. In many cases, problems may arise again with the workability of the land, crop yields and disease stress. But what we can do in many places is put the clog back in the drain every now and then so the water doesn’t run out constantly all year round. With a number of adjustments, the farmer can adjust the groundwater level. It pulls the stopper for plowing and sowing, but when it’s done, the stopper can be pushed back inside. The Belgian Soil Science Service has proven that water level control in the Kempen and Maasland regions can bring in additional yields of between €100 and €450 per hectare per year.

More and more researchers and governments are studying level-controlled or adjustable drainage and local farm dams in Flanders along with the sector. Although the idea is not new, many questions are still being applied. I will try to answer these questions together with my colleagues from almost all Flemish practice centers and other research institutes in the coming years. In what locations are the soil and water system suitable for precise regulation of the groundwater level? Can we even pump more water into those systems, say from a river or from a purification plant? How can farmers optimally control the water level to increase the yield of their crops as well as help replenish groundwater? How can farmers and water managers work together to reconcile all water system functions as closely as possible? In particular, the question of how all users will move towards a democratic and sustainable management of our water together is a huge challenge!

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