Earlier this summer, I found some great information about how surface waters (streams, lakes, etc.) and groundwater (aquifers, etc.) affect one another; I summarized some of that here.
Something I don’t recall was mentioned in my source for that was the broader impact on forests, although obviously, if you cut stream flow through a forest, the trees near that stream will be affected (and so if you had a well that impacted the stream or other surface water, that could draw down the water available to the plants).
So a study in Australia found that disruptions to groundwater can have an impact on trees a significant distance from the immediate area of impact:
Pfautsch found the water use of trees some several kilometres away from mine sites was sensitive to changes in groundwater levels.
“Where the water table had fallen to 19 metres below the surface, water use of trees was much lower compared to trees where the water table remained unchanged at around six metres below ground level,” he said.
“The tight connection between water use and the growth of trees implies that a reduction in water use will lead to a reduction in growth. In extreme cases trees can die of thirst.”
Pfautsch’s study suggests the implications of changing groundwater levels owing to mining can potentially extend beyond the boundaries of mines. Farmers on the Liverpool plains draw down on the groundwater to grow their crops.
He points out that the environmental impact study the mine is required to do needs to take more area into consideration than it has – look at trees farther away, including an area containing endangered trees – as well as do more monitoring of how plants are getting their water, since at this point it hasn’t done enough work to actually understand where plants in the area are getting their water from, and was making assumptions that aren’t necessarilytrue.
“For example, the environmental impact statement for the planned Shenhua Watermark coalmine concludes that because groundwater naturally occurs 20 metres below the surface where plants supposedly cannot reach it, the existing vegetation communities within the project boundary are not depending on groundwater,” he says.
“Hence, it is believed lowering the groundwater table will have no effect on these vegetation communities. But the source of water accessed by the existing vegetation seems to have never been determined, and trees often rely on capillary water in soil that rises up from the water table.”