Groundwater is a very useful resource. If handled properly -

- it'll deliver clean and sustainable water for irrigation as well as drinking.

But there are many threats to the groundwater.

Pollution and climate change are the more important ones.

Climate change comes in different forms.

But a typical picture is that dry zones get dryer, and wet zones get wetter.

In terms of groundwater, the most severe problem is the lack of precipitation.

This is something we've seen in many regions of the world -

where dry periods became longer and more extreme over the last couple of decades.

On top of that, the rains are heavier and more extreme.

The extended dry periods will cause the groundwater table to decline.

Any additional groundwater extraction, for drinking water or irrigation - will only accelerate this natural depletion.

On top of the general drought problem, the rain events are also more extreme - which poses a problem for the groundwater recharge.

The reason is that when we have these extreme events - a lot of the water runs off directly from the surface into streams and rivers - without having time to infiltrate to form new groundwater.

Other areas, like Denmark, see a different effect of climate change.

The picture we see here is that we get more rain throughout the year.

The immediate effect is a rising groundwater table.

In parts of Denmark - the water table has risen to less than a meter below the surface.

The immediate consequence is that in the event of heavy rain - we'll likely see flooding.

The reason is that the buffer capacity of the ground to hold water - is very limited.

The last big effect from climate change is salt water intrusion.

As the general sea level rises - salt water will penetrate deeper into the coastal-near aquifers - and thereby displace the freshwater resources.

The consequences may be mitigated - by moving the groundwater resource extraction points further inland.

On the other hand, a lot of people live in these coastal-near areas - and depend on the freshwater resources.

Climate change is affecting our groundwater resources in many ways.

However we look at it, the processes are ongoing - and we've only started seeing the full consequence.

Next to climate change, pollution is a serious threat to groundwater.

Pollution comes in many forms such as leakage from unprotected landfills - or pesticides from farming.

Groundwater is often quite old, which means it may take several decades - before we see the full extent of pollution.

In Denmark, the average age of the groundwater is about 50 years.

This means we'll likely see pollution coming into our groundwater - even though the sites that polluted the groundwater are not active anymore.

Solving or mitigating the consequences of climate change or pollution - requires knowledge.

Knowledge about where the water is. Is the aquifer small or big?

Do we have salt water underneath? Where is the water being replenished from?

And is there a polluting source nearby?

Many of these issues are being addressed when designing new well fields.

We try to gather as much information as possible.

We map the layers of the underground.

We identify the recharge zones to see if there are possible contaminant sources.

Then we also model the flow of water to establish a sustainable extraction rate.