Monday October 24, 2022

University of California, Santa Barbara

Scientists at UC Santa Barbara (UCSB) have recently determined that heavy reliance on groundwater is increasing the risk of contamination in our drinking water. 

In an average year, groundwater makes up about 40 percent of California’s total water supply. During severe droughts, which have increased in intensity and frequency due to climate change, some regions of California get up to 60 percent of their water supply from groundwater wells. Because we rely so heavily on groundwater, it is important to understand the potential risks of relying on this source to such an extent.

So what exactly is groundwater? Just like digging a hole at the beach, when people drill deep enough into the ground, water begins to fill in. The water table is the level at which the ground becomes saturated with water. 

There are many other materials, however, that make up the ground and can affect the quality of groundwater. Some, like sandstone, are porous and precipitation is easily able to percolate (filter) through. Others, like clay or granite, are not as permeable, and water takes a long time to filter through. This means that the water table is not at the same level everywhere — it depends on the soil and rock that the ground consists of. As precipitation seeps deeper into the ground, a process that can take thousands of years, the contaminants from the surface are filtered out and broken down. Today, we use complex drills to dig deep wells into the ground, surpassing the layers of less permeable elements in order to find a consistent source of groundwater. This can disrupt the natural filtration process in the ground, increasing the risk of contamination in the water. 

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