What is an ephemeral stream?
An ephemeral stream is a stream whose bed lies above the water table, so that the stream flows only when the rate at which water enters the stream from rainfall or melt water exceeds the rate at which water infiltrates the ground below.
Ephemeral streams, also known as intermittent streams are seasonal streams, which are channels that provide drainage, holding water after the winter snow melts and during seasonal rainfall periods of autumn and spring. By mid-summer, these ponds almost always dry up completely.
Many factors are involved in the formation and preservation of ephemeral streams. The small depressions are typically the result of glacial sculpting activity. Over years, woodlands formed, creating an isolated environment. The underlying layer of the earth is generally an impermeable layer of silt loam, clay, or bedrock, which prevents fast absorption or drainage. The length of time these streams hold water depends on a variety of factors, including the amount of spring rainfall, depth of the land depression, and the rate of evaporation. Streams with a closed canopy (heavy tree cover) may delay the warming of the stream and slow evaporation. Streams with an open canopy will allow for faster warming which could speed up evaporation. The biology of the pool is controlled by water depth, temperature, pH, pollution, duration of water in stream, and other conditions.
Why does Tynehead have ephemeral streams?
Tynehead has ephemeral streams all over due in part because of the heavy rainy seasons between October and May averaging over 150mm of precipitation each month. This rain when add with the density of the surrounding ground consisting of clay and hard bedrock basin, prevents water saturation in the ground. In the centre of this area of the park is an ephemeral pond/marsh which is at a high point of the area. During rainy periods this is where water accumulates gradually supplying water to the ephemeral streams of the area.
Why are ephemeral streams important?
Ephemeral streams provide a crucial source of water in otherwise dry landscapes and so are of great importance to consumptive, environmental and recreational water users. Although often unnoticed, ephemeral streams support millions of dollars of agricultural and other economic activity, as well as domestic supplies. Ephemeral ‘losing’ streams are critical to the ecological biodiversity of the landscape by preserving certain animal and plant species. Because these ponds dry up in summer, they contain NO FISH! This is especially important for the breeding of amphibians and certain invertebrates who can lay their eggs when the pool contains water in spring without worry of being eaten by fish, and then develop in the dry habitat in summer.
Many species rely on vernal pools as a water or food source. Common wetland plants found at the pool include yellow water crowfoot, mermaid weed, Canada bluejoint grass, floating manna grass, spotted cowbane, smartweeds, orange jewelweed, and sedges. Besides providing a necessary breeding habitat for amphibians, these plants also provide a feeding, resting and breeding habitat for some birds, and a source of food for many mammals.
Earthcache Logging requirements:
In order to log this earthcache you need to email the cache owner the answers to following questions:
The close to the posted coordinates is a mock ephemeral stream display the posted coordinates will take you to the actual stream, and around the park is the network of tributaries that feed into this main stream. I challenge you to comment on the ephemeral stream nearby and around the perimeter trail of the park. From this location you are near the ephemeral story station from this you will be able to answer the following two questions:
1) Name three bodies of water that this ephemeral stream drains into?
2) Name three species that live in and around the ephemeral streams?
3) Count the number X's that you see on the bridge and give me the count?
Supply the following information in your log post:
3) In your log describe (photo optional) the ephemeral stream and the type of plants it has.
4) Include in your log if the stream dry or wet during your visit?
The earth cache has been approved by the Metro Vancouver Parks and is located on the new Tynehead Perimeter Trail which features several "story stations", that will reveal the ecological history of the park through interpretive kiosks and public art. This cache is one of the "Story Stations" called "Ephemeral Stream"
Parking is located on the south side of the park adjacent to 96th Avenue. A parking waypoint has been provided.