Quite a lot of rain falls, so how can there be a shortage of drinking water?
It's because our drinking water comes from a layer that isn't simply topped up. Rainwater takes decades to reach this layer. This layer is like a very large 'bubble' of water tens of thousands of years old, starting in the Ruhr area and running all the way to Antwerp.
Our drinking water in the Netherlands also comes from this layer, which is also called an aquifer. This large area consists of rock or sediment in which our groundwater collects and flows. Part of this water was once rainwater that seeped through the soil and ended up in this layer after decades. In many places in the Netherlands, rainwater actually doesn't seep down but stays in the top layer — which is why water lies on many meadows. A clay subsoil lets water through even less easily than a loose sand layer.
Replenishing the aquifer is therefore a very slow process: rainwater moves through the soil only very slowly, and it can take decades before it reaches the layer where the water level is measured. That also depends on the permeability of the soil and the amount of rainfall in the area. Those same clay and sand layers do provide natural filtering that we cannot influence.
Excessive use of the clean drinking water from this layer can lead to depletion of our most important water source. The water level in this aquifer has been falling for some time, and demand for drinking water from this layer is currently much greater than what is replenished. Because rainwater takes decades to reach this bubble, an imbalance arises: far more goes out than comes in. In the long term this can lead to wells running dry and damage to the ecology of the area.
Your garden sprinkler, filling a paddling pool, washing the car or showering a little too long? That's not where the big consumption comes from. That is mainly found at factories: at present, factories take in clean (drinking) water, including from this layer, use it in production processes and then discharge it — treated according to the applicable standards, but reuse is not yet standard practice.
European legislation is on its way to protect our waters against pollution and excessive use of our groundwater. That legislation should encourage factories and the agricultural sector to use water more sustainably, so that water use remains sustainable in the long term. Up to 80% of the treated water would then be taken back into the production process instead of being discharged, as often happens now — and that makes the difference. This gives the water level the chance to stabilise again over the coming decades, before an irreversibly low level is reached.
Even though sometimes more rain falls for months than has ever been measured, a shortage of drinking water and a low water level can still arise because we haven't been careful enough with our precious water. Reusing treated water at the end of the production process can ease the pressure on our drinking water sources.