Thirty-two miles downstream from Lees Ferry, the Colorado River cuts into the Redwall Formation, exposing ancient groundwater passages. Just beyond the great bend at the mouth of South Canyon, a gushet of whitewater cascades down the limestone cliff on the right side of the river through a jumble of greenery and into the main stream of the Colorado River. On his historic 1869 expedition through Grand Canyon, Major John Wesley Powell named this springs ecosystem in honor of his associate and noted botanist, Dr. George Vasey. The Vaseys Paradise groundwater channel is a lengthy karst system, one of many in this section of Grand Canyon, and delivers water from the North Rim into the Colorado River. Like all karst systems, groundwater flows through conduits and fractures. This conduit system has been mapped for more than 2 miles from its emergence in Grand Canyon. Vaseys flows are highly variable in response to precipitation and snowmelt: years with high snowpack have much greater spring flow between April and June compared with drier winters. As summer progresses, the flow decreases, although summer monsoons occasionally prompt brief spikes in flow. In very dry years, such as 1977, Vaseys Paradise goes nearly dry. In 2014, although some reported that the springs had gone dry, NPS hydrologists found some flow. From 1950 through 1997, flow averaged 10 gallons per second, varying nearly 6-fold from fall and winter to the May/June snowmelt. During cold winters, Vaseys becomes an enormous fountain of ice. Flow from the three sources has shifted since 1969, with most discharge now issuing from the downstream pourouts. Vaseys water is dolomitic, its carbonate-rich discharge having approximately equal calcium and magnesium concentrations, but relatively little sulfate, chloride, silica, or sodium. The water is fairly dilute in comparison with most Grand Canyon springs, due to its short groundwater residence time. Vaseys water is chemically similar to Bright Angel, Shinumo, Tapeats and Deer Creeks, which also are dolomitic, although Vaseys may have a higher concentration of nitrogen. Vaseys water temperature is nearly constant, averaging 16.1°C (61°F) but ranging from winter lows of 14.4°C (58°F) to August highs of 19°C (66°F) from 1994-1997.
Consistently warm water mitigates variability in air temperature at the springs. The site receives summer sunlight only in the morning hours, and therefore is more hospitable to cool-temperature plant and animal species. Vaseys Paradise is a good example of a gushet springs ecosystem, one in which water pours out of a steep cliff face and glides in a white cascade that aquatic ecologists call “madicolous” habitat. Madicolous habitat supports an unusual array of species that are adapted to living in shallow, torrential flow. Although poorly inventoried, the madicolous species found at Vaseys include mosses, rare aquatic beetles, a small moth whose larvae are aquatic, and, during winter, American Dippers. Many more species live in the far less stressful hanging gardens and steep wetlands surrounding the cascades. Vegetation there includes a profusion of poison ivy (one of only three populations along the river in Grand Canyon), helleborine orchid, Emery’s sedge, western redbud, narrowleaf bricklebush, coyote and Goodding’s willows, water-cress, a rare-in-Grand- Canyon population of water smartweed, and both a red and a unique yellow variety of cardinal monkeyflower. Vaseys habitat supports vivid dancer damselflies, caddisflies, a unique midge (Metriocnemis stevensi), and the second highest concentration of land snails known from Grand Canyon springs. Nine snail species have been documented at Vaseys Paradise, including the species once known as the Kanab ambersnail (Oxyloma hayendi kanabensis) that has subsequently been taxonomically redescribed as the Niobrara ambersnail (O. h. haydeni).
The Vaseys Paradise Niobrara ambersnail population was discovered in 1990 living in the monkeyflowers and sedges on the upstream side of the channel. Originally identified as Kanab ambersnail, Niobrara ambersnails were listed as endangered due to habitat loss in Utah. Ambersnails are widespread across the United States in wetland habitats, but the 14 species are difficult to distinguish. Along with subsequently discovered Niobrara ambersnail populations at -9 Mile Spring in Glen Canyon and at Indian Gardens in Grand Canyon, these are the only three naturally occurring ambersnail populations known in Arizona. The ambersnail feeds on bacteria and algae on dead, decaying stems of monkeyflower, sedges and other wetland plants, and on non-native watercress. Hermaphroditic, it grows to maturity in August, mates and produces several gelatinous egg masses, each with dozens of eggs, and then it dies. The eggs hatch soon after and the young snails mature until mid-October. They then find sites to seal their shells with a mucous gasket for winter dormancy. Unfortunately, their choice of overwintering sites is often poor: many settle on dead poison ivy leaves or twigs that are easily blown away. Those that settle on rocks and out of the flood zone may survive the winter, emerging about halfgrown in April to complete their life cycle. However, the ambersnails at Vaseys face additional challenges. Among their enemies is a native flatworm, Leuchochloridium cyanocittae.
The complex life cycle of this internal parasite begins in the intestines of a songbird, where mature flatworm parasites release eggs. The eggs are defecated onto wetland vegetation, hatch into miricidia, and are consumed by unwitting snails. The miricidium grows in the digestive tract of the snail, eventually occupying as much as half the body volume of its host. When mature, it produces sporocysts—acid pink and green, worm-like lozenges that contain hundreds of cyst-like cercaria (the next life stage of the parasite). At that point the parasite controls the snail’s behavior, “driving” it from the protective vegetation into the open and rapidly flashing the pink and green sporocysts from the snail’s eyestalks. Potential host songbirds are attracted to the movement and color, attack the vulnerable snail, whereupon the sporocysts are ejected out the snail’s eyestalks and consumed by the bird. The cercaria then completes their parasite life cycle in the bird’s digestive tract. Unfortunately for the snail it does not die at this point: the micidium lives on inside the now blinded snail, producing additional pairs of sporocysts, repeating its avian advertisement antics until the snail finally dies in late summer. Vaseys is the only locality known for this flatworm species in Arizona and one of the few sites known in the western US. About 10% of the Vaseys ambersnails are infested with the flatworm, making the parasite much rarer than the endangered snail.
Vaseys Paradise is a remarkably rich site for interpretation about strange, unique features, creatures, and aquifer connections in Grand Canyon. Threats to this large springs complex are primarily external to Grand Canyon—groundwater pumping, climate change, and forest management on the rims. However, much of Vaseys’ watershed is protected, and with research and monitoring attention, the supporting aquifer can be protected to ensure the springs continue to flow in their unique and wild way.