It’s raining again – are all the drought-related problems now solved?
It’s raining again and it’s not as hot, so less water is evaporating. But does this mean the drought is now over and can we return to ‘normal’? Unfortunately not; we are currently some 300 mm short of the required rainfall, so the 70 mm of rain expected on average over the next two weeks is not enough. What will happen in the coming period to the Rhine and Meuse, and to the groundwater beneath our feet?
What does the recent rain mean for Dutch rivers and water distribution?
The lowest discharge levels of the Rhine at Lobith were recorded on Monday 17 August and Tuesday 18 August, at around 560 m³/s.
As a result of the rain falling upstream – particularly in the Alps – the flow rate at Lobith will rise over the next two weeks, possibly reaching as high as 700 m³/s (Rijkswaterstaat flow forecast of 17 August). That is a significant increase, but the flow remains well below the National Water Distribution Coordination Committee’s (LCW) criterion for this month of 1,100 m³/s. This means that the drought problems have not yet been resolved by the current rainfall.
What does this mean for shipping?
The main bottleneck for shipping bound for Switzerland is currently Kaub in Germany, where water levels were too low for vessels to pass through. With this modest increase in discharge, the problems have not yet been resolved. It is likely, however, that from the weekend onwards, many vessels will once again be able to sail past Kaub with reduced loads. The situation further downstream will not improve until a few days later.
What is the outlook for Europe?
Over the next two weeks, around 70 to 100 mm of rainfall is forecast for the Alpine region within the Rhine catchment area (source: KNMI); this is above the long-term average for the month of August and will contribute to the aforementioned rise in Rhine discharge. Rainfall is also expected in Germany, with amounts of 50–70 mm. Both in the Rhine catchment area and in the Netherlands, this means that the rainfall deficit is still far from being made up.
The Rhine as a rain-fed river
In September 1998, our colleague Frans Klein wrote the report The Rhine in the Long Term. The study focused on the question of how the Rhine basin can adapt in the long term to developments such as higher river flows, sea-level rise, land subsidence and increasing pressure on land use. A resilient Rhine is better able to cope with unexpected changes and extremes such as high and low water levels.
It is now clear that the Rhine is developing into a rain-fed river. Due to rising temperatures, a greater proportion of winter precipitation will fall as rain rather than being stored as snow. This will cause winter discharge to increase, whilst the contribution of meltwater to summer discharge will decrease. As a result, discharge during the summer months will be lower.
Glaciers are still melting now and in the coming years, but they are steadily decreasing in area and volume. In a few decades, this contribution to late-summer flow will become very small.
Frederiek Sperna-Weiland, water availability expert at Deltares
Download the publication on the Rhine
What are the forecasts for the Meuse?
The flow in the Meuse is also low for this time of year. We have now been below the LCW criterion for several days (3-day average flow <25 m³/s). As a result of the rain currently falling and the rain forecast, the flow will also rise this coming week, and 3-day average values of 25 or 30 m³/s will come back into the picture (RWS flow forecast, 17 August 2026).
What does the current rainfall mean for groundwater levels?
Firstly, the rain must replenish soil moisture. If we also want to see an improvement in the groundwater level, much more rain is needed. The fact that soil moisture is replenished first is beneficial for the crops growing in the fields and for people’s gardens, where the grass will look a bit greener again after this week’s rain. However, the recovery of the groundwater supply takes longer, and there are also significant regional differences across the Netherlands. In the polders, groundwater levels will recover more quickly than on the higher-lying sandy soils, where groundwater levels have fallen more deeply. The flow in streams will only return to normal once groundwater levels have risen.
Download publication on sandy areas in the Netherlands (dutch)
What is the effect of drought on groundwater?
During a drought, there is little water available, yet there is high demand for both surface water and groundwater. Farmers then resort to irrigating their crops, which is sometimes at the expense of nature. You will therefore see that almost every water board has imposed bans on abstracting water from surface water bodies. This makes sense because if there is too little water in a stream or ditch, it has a direct impact on life in the watercourse, such as fish. What is less well known is that the extraction of groundwater also affects the flow in ditches and streams. Furthermore, groundwater levels fall as a result of extraction, with consequences for wildlife that depends on groundwater. However, bans on groundwater extraction are only introduced sparingly and often later than is actually necessary.The buffer provided by our groundwater could be used more wisely. Research is needed to determine how we can do this more wisely, whilst taking both agriculture and nature into account.
Perry de Louw, groundwater and drought specialist at Deltares
In any case, it seems necessary to set extraction limits, both in terms of area and time, for each region, depending on the condition of the (groundwater) system (dutch) This would prevent damage to nature whilst still allowing for irrigation. Building up an additional groundwater reserve during periods when there is sufficient water provides a buffer. Farmers who create such a buffer could be permitted to extract groundwater for a longer period.
Our water system of ditches and watercourses is still designed to drain water away as quickly as possible. This developed historically to serve agriculture, which needs to work the land as early as February and March. But as a result, our landscape can be seen as a colander through which water flows away easily.
Restore the landscape’s natural sponge-like function
If we can retain groundwater for as long as possible, we will benefit during the summer months. This helps to mitigate the effects of drought. That ‘colander’ mentioned earlier should, in fact, become a sponge that absorbs the water and releases it gradually. This also leads to higher groundwater levels and stronger seepage flows, which help to restore the structurally parched natural environment.
This does, however, entail a structural change to the water system – one that must be implemented comprehensively and on a large scale across the entire landscape if it is to be effective. The result will be a structural rise in groundwater levels and stronger seepage flows towards nature reserves. The downside is a greater risk of flooding; after all, a sponge will eventually become saturated. Where this leads to problems, we must take additional measures. To preserve nature reserves for the time being, it is already highly effective to focus on areas surrounding wetland nature reserves and stream valleys. This is an important step in combating the structural drying out of nature reserves.
Download the publication 'The Sponge Effect of Landscapes in the Netherlands
