Self Guided tour of Tule Ponds at Tyson Lagoon
The Tule Ponds at Tyson Lagoon provides a unique opportunity to see how the needs of humans in an urban setting and other organisms can mutually co-exist. Before humans arrived in what is now Fremont, many organisms like mammals, birds, insects, and fish inhabited the area. As areas become urbanized (populated with people and their buildings) the natural order of things starts to change.
Prior to urbanization, water from rain soaks into the ground and slowly percolates into the layers of the soil and bedrock. If there were more rain than the earth could handle, the water would “run off” causing floods. These flood waters brought nutrients from the nearby hills, and the plants especially benefited. As people built homes and laid down asphalt and cement for cars to use, water flows more quickly. They usually build homes in the flat area near a river, which is referred to as a flood plain. The rains caused flooding and damage to many homes. To prevent floods, engineers developed ways to allow the water to flow quickly through man-made channels that would bring water to the San Francisco Bay edge. It works, but it also causes valuable lost of habitat for other creatures.
The Tule Ponds at Tyson Lagoon acts as a flood area to slow down and contain water on its way out to the bay. After water leaves the lagoon it flows through earth or concrete-lined channels out to the bay. This area helps to prevent floods, but also acts as a natural place for organisms to thrive.
These wetlands also help to remove substances that enter the system from residential, urban, and agricultural runoff. Some of these substances are considered pollutants and may be toxic to different types of organisms. Residential and urban runoff in this area would include garbage, pesticides, oil and grease, organic matter, and heavy metals. Agricultural runoff from nearby small farms would include pesticides and nutrients. The frequency of these substances is intermittent and dependent on winter rains.
As you walk along the trails, you will learn how water is being cleaned before it enters the San Francisco Bay and how it is used to increase habitat for many kinds of organisms. Stormwater enters through a large pipe into Pond A, and then flows into Ponds B and C and then enters into Tyson Lagoon. When the water reaches a certain level, it flows into an outlet that parallels Mowry Ave.
Each of the 6 stations highlights a function of the entire ecosystem. After you go through the different stations you may want to look at the many plants and birds that can be found in this unique area.
WARNING: Please remember to keep on the trails and don’t disturb the wildlife. Throwing rocks is not permitted and chasing wildlife is prohibited.
During a storm event, water will run off from asphalt, cement, and saturated soil Sediments, chemicals, and trash flow with the water. Ponds B and C use logs to help retard the flow of objects that float, like oil and garbage. Motor oil coats fish gills, preventing the fish to use dissolved oxygen in the water. Oil can coat bird wings, making flight difficult and prevents feathers from “fluffing up” to provide insulation against the cold. You can notice that the constrictions between the ponds help to narrow the flow trap these lighter objects. The removal of harmful objects protects the wildlife.
Concentrations of sediments, chemicals, and garbage change during a storm event. The early part of a storm transports the largest amount of larger particles whereas the later stages of storms have a higher percentage of dissolved hydrocarbons and dissolved metals. The velocity of the water also slows as stormwater enters the Tule Pond system. This allows heavy particles to drop out of the system first.
Pond A is designed to slow the flow of water to allow suspended particles to drop out of the water column. This increases the water quality of the water so it is less of a potential hazard when it enters the San Francisco Bay. The suspended particles range from heavy metals, such as copper (Cu), lead (Pb) and zinc (Zn), to simple particles like sediment and soil. The particles increase turbidity and prevent the penetration of sunlight to phytoplankton. Increased nutrients from fertilizers (such as nitrogen (N), phosphorus (P), and Potassium (K) create algal “blooms.” As the plants decompose they cause conditions unfriendly to organisms in the water (eutrophication). Lead comes from paints, wood staining products, and emissions from diesel and gasoline operated vehicles. Zinc is from automobile tires, paints, and wood staining products. Copper comes from plumbing, electroplating processing wasters, brake pads in automobiles, and algaecides. In high dosages these substances can be hazardous to organisms that live or frequent the ponds.
Residential and urban growth in a watershed increases water runoff. When you construct a home, industry or road, water is then prevented from percolating downwards into the ground and flows into a series of connecting pipes. If you look at the beginning of Pond A you will see a large pipe. Water in this pipe comes from a series of storm drains connected by underground pipes.
Water seeks sea level, so drainage in a watershed is determined by topography. Drainage in the Tule Pond is restricted to a watershed that includes the surrounding area. Runoff occurs when the zone of aeration (where plants take up water) is saturated and when excess water cannot percolate into the ground. Runoff contains suspended particles such as silt as well as dissolved substances. Some of the particles are natural, from erosion caused by weathering of the nearby hills. However some substances are added by humans, including heavy metals, garbage, and dissolved chemicals.
Water quality is frequently enhanced as water passes through wetland. Plants help to slow the flow of surface run off and cause sediment to settle out. Living aquatic plants like algae and large emergent plants like tules and cattails, add dissolved oxygen to water during photosynthesis. Wetland plants support much of the life in open water, and plants like cattails and tules provide shelter for larger animals living in the pond.
Wetlands have characteristic vegetation that can tolerate being submerged in water. Wetland plants do not require an elaborate way of capturing water like trees. Certain plants in these vegetated waterways are effective in removing metals from storm water. Metals accumulate near outflow and are not transported very far downstream. Zinc is an exception because it stays in dissolved form.
Butterflies are indicators of the overall health of an ecosystem. Loss of habitat is a major threat to butterflies as open meadows turn into residential areas. Butterflies are beautiful but are important pollinators of many plants. They also provide a food source for many birds, mammals, reptiles and even other insects.
This butterfly meadow will not only help repopulate native butterflies but will be a home of many native plants that serve as a food source for the caterpillars that will change into a chrysalis before the butterfly emerges. The nectar can be also used by other animals like hummingbirds.
Wetlands are among the most productive ecosystems in the world. A fresh
water marsh is as productive as a tropical rain forest. Wetland plants
are specialized because they can withstand water levels that most land
plants cannot. Bacteria, protozoa, and fungi are bountiful as
decomposition of organic matter releases nutrients. These microscopic
critters are eaten by larger invertebrates like arthropods and mollusks,
that in turn are eaten by amphibians, reptiles and fish.