More than 30% of all of Earth’s freshwater is underground. This may not sound like much, but when you consider that just 0.3% of all freshwater is found on Earth’s surface – in the form of rivers, lakes, swamps and wetlands then is begins to look like a huge amount (the rest of Earths freshwater is locked up in icecaps and glaciers, and in the atmosphere – incredibly, all of this combined only adds up to 2.8% of all of Earth’s water as the rest (97.2%) is saltwater in the oceans). The good news is that these underground reserves of water are really important and undergo some interesting processes while it’s down there. A small percentage of this groundwater returns to the surface as springs. The natural movement of water around different parts of the planet is known as the hydrologic cycle.
As the name suggests, spring creeks are formed from groundwater bubbling to the surface with enough volume to form flowing water, or, a creek. These can be very small and travel just a small distance before the water evaporates or returns to the ground, or they can go on to be the tributaries that help to form larger rivers downstream.
Spring creeks are important for many reasons, and fly anglers love them for their unique qualities. For one, water that forms spring creeks is generally crystal clear – perfect for sight fishing when you need to see the movements of trout and what hey are eating. The reason the water is so clear is that the rock and sediment where the groundwater has been slowly moving through (sometimes for thousands of years) acts like a big filter, or water purifier. The amount of filtering that occurs has to do with the porosity and permeability of the rock and sediment the water travels through. In this way, any pollutants or cloudy sediments that have made it into the groundwater from when it arrived from the surface has been slowly filtered out to produce super-clean water in many cases. Not surprisingly, some of this water gets used for drinking water for us humans.
Sometimes, the water that bubbles out into springs has picked up important minerals from the rock that it travels through. These minerals can help to promote a healthy creek environment allowing healthy water plants and riparian vegetation to grow, which are fertilized by these minerals. This in turn attracts fauna such as insects, which attracts birds and fish etc. to make a healthy self-sustaining ecosystem within the creek. Another quality that water can pick up as it bubbles to the surface is acidity or alkalinity, which depends on the amount, and type of ions in the water. The famous chalk streams of southern England produce alkaline water, and this quality helps to promote plant and animal growth in the rich waters too.
Another important quality of the water in spring creeks is the stable water temperature. The water entering these creeks from the ground has been cooled (or heated – if it runs close to geothermal sources) from its time spent underground. The actual temperature will vary, depending largely on the depth of the underground aquifer the water has been buried in. To us fly anglers the spring creeks of interest to us come out at the perfect temperature for trout to live in. This has helped spring creeks being described as ‘climate change proof’ and drought proof (due to the regular supply of water).
Spring creek fisheries are sometimes known to be highly ‘technical’ – which means the trout living there can be really picky eaters and easily spooked. This makes them a great challenge for experienced anglers who travel great distances to experience the unique fishing opportunities that spring creeks offer.
See below video for an example of the magic that spring creek fly fishing offers.
Video Credit: Catch Magazine
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