Rachael Marques, Watershed Specialist

 

This year, we’ve delved into how our region’s geology influences various water resources. Previously, we examined groundwater interactions; this month, we turn our focus to surface waters.

 

As the Watershed Specialist here, I talk a lot about watersheds. But what are they? Shown in the image below, they are essentially common drainage areas, or areas where all precipitation and water drains to a common point. These are dependent largely upon geology and the rock formations in the landscape. These formations, such as mountains and valleys, were created long ago mainly through the action of tectonic plate movement. The divides, or boundaries, in a watershed are often high points, such as a mountain. In a rain event, the water will go to one watershed or another, depending on where it falls. In the example of a mountain, one side may be draining to one watershed while the other side could be draining to another watershed entirely. The shape of the landscape and its formations have a direct influence on the size and shape of our watersheds!

 

 

The geology of the area doesn’t just affect the shape and size of a watershed, it can also affect the quality of the water bodies within it. Here at PCCD, we frequently talk about erosion, the process by which soil and rock can be gradually washed away by water. A large part of what our Resource Conservationists do is help prevent excess erosion due to human activities by assisting in the implementation of erosion and sediment control best management practices. Different types of rocks and soils can be more or less prone to being dissolved by rain, high water, and other weather. For example, many areas in Pennsylvania have “Karst” geology, meaning that is made up mainly of rocks such as limestone. Limestone is considered a “soluble rock” or a rock that is easily dissolved in acidic water. The rock gets dissolved and washed away potentially forming things such as sinkholes and caves, greatly affecting the overall hydrology of an area as well. The erosion of these soluble rocks can lead to higher calcium and manganese concentrations in waterbodies nearby as the material is dissolved and then carried down the watershed.

 

Understanding the interactions between geology and surface water quality is essential for effective water resource management. By recognizing how geological features influence water chemistry and ecosystem health, we can better protect and preserve Pennsylvania’s valuable water resources.

 

https://www.usgs.gov/mission-areas/water-resources/science/karst-aquifers#overview

https://www.ngwa.org/what-is-groundwater/About-groundwater/dissolved-mineral-sources-and-significance

Stream Connections: Benthic Macroinvertebrates, Native Fish and PA Geology