Planet & Ocean Discovery Series: Guam -Inland Waterways
Habitats & Adaptations
Background
Guam’s interior is threaded with a network of rivers, streams, and freshwater reservoirs collectively known as inland waterways. Despite their modest size, these water bodies are vital ecosystems supporting diverse aquatic life. They provide invaluable services to the island, including freshwater supply, irrigation, and recreation. Beyond their practical uses, these waterways enhance Guam’s natural beauty and cultural heritage. Safeguarding and restoring these resources are crucial for preserving the island’s ecological balance, protecting native species, and mitigating the impacts of climate change.
Key Vocabulary
- Agriculture
- Anaerobic
- Brackish
- Concentration
- Conservation
- Ecological Balance
- Drought
- Precipitate
Learning Objectives
- Students will learn how the diverse habitats of Guam’s inland waterways support aquatic species and contribute to ecosystem balance, including adaptations of species such as the freshwater goby to low oxygen levels and high temperatures.
- Students will investigate how species in Guam’s freshwater environments, such as the Indo-Pacific tarpon and walking catfish, adapt their behaviors and physical characteristics to thrive in their unique ecological niches.
- Students will examine how environmental factors such as temperature and water flow dynamics affect the oxygen concentration levels in Guam’s freshwater systems and the survival of species like the freshwater goby.
Next Generation Science Standards Alignment
LS2.C: Ecosystem Dynamics, Functioning, and Resilience: The students will learn how inland waterway dynamics and the adaptations of freshwater organisms contribute to a well-functioning ecosystem.
LS2.D: Social Interactions and Group Behavior: The students will learn how species adapt to their surrounding environment and habitats, developing advantageous traits that benefit them within their specific ecological niche.
Guam’s inland waterways exhibit a diverse range of flow rates, depths, and water quality, providing a mosaic of habitats for a variety of aquatic life. These waters support a rich tapestry of species including fish, amphibians, reptiles, and aquatic plants, each uniquely adapted to its environment. Freshwater organisms in Guam have evolved specialized respiratory systems, streamlined bodies, and exceptional maneuverability to thrive in these dynamic conditions. Some species, such as the resilient freshwater goby, have developed remarkable adaptations to tolerate the island’s often challenging water conditions, including low oxygen levels and elevated temperatures.
Guam’s two major rivers are the Ylig an the Talofofo rivers. The Ylig being the longest flowing from the central highlands to the western coast. Both rivers provide the island with a place to swim, fish and hike. The Talofofo river is known for its scenic beauty and waterfalls which provide a popular destination for locals and tourists. Guam also has smaller rivers that provide habitat for many species of birds, fish and other wildlife. Two significant smaller rivers are the Chalan Pago and the Pago rivers.
Characteristics
Guam’s freshwater resources are primarily dependent on rainfall. Surface water, nourishing the southern half of the island, complements the groundwater found in the Northern Guam Lens Aquifer (NGLA) that sustains the north. These vital water bodies serve as both habitat and nursery for a diverse array of aquatic species. The island’s hydrology is characterized by a gradual transition from saltwater to brackish water and finally to freshwater. This unique arrangement, often described as a freshwater lens, overlays a layer of brackish water which in turn sits atop saltwater. The freshwater lens happens when the island has rain that infiltrates the ground becoming groundwater. The freshwater then sits on top of the saltwater table and provides the island a source of freshwater for drinking, agriculture, and other uses. This complex hydrological system is crucial to the island’s ecology and supports a delicate balance of life.
Species
Oxygen
Oxygen concentration levels within Guam’s inland freshwater waterways are subject to constant fluctuation. Several environmental factors significantly influence these levels. Temperature emerges as a primary determinant, with rising temperatures leading to reduced oxygen solubility in water. Additionally, water flow dynamics play a crucial role. Stagnant or slow-moving waters tend to have lower oxygen concentrations compared to swiftly flowing streams. Over-pumping of the Northern Guam Lens Aquifer (NGLA) exacerbates the issue by causing increased salinity and decreased oxygen levels, further impacting the delicate aquatic ecosystem.
The freshwater goby, a remarkable species found in Guam’s waters, has evolved extraordinary adaptations to survive in these challenging conditions. These fish have developed the ability to tolerate both warming waters and extremely low oxygen levels. Through anaerobic respiration, they can endure prolonged periods in environments where oxygen is scarce, a feat unattainable for most other aquatic organisms. This unique physiological adaptation allows the goby to thrive in habitats that would be inhospitable to many other species, highlighting the remarkable resilience of life in Guam’s inland waterways.
Environmental Importance
Background
Guam’s inland waterways are ecological lifelines, nurturing biodiversity and contributing to overall environmental health. As critical breeding and feeding grounds for a diverse range of species, these water bodies support both resident and migratory wildlife. Beyond their ecological roles, these waterways act as natural filters, improving water quality by trapping sediments and pollutants. Their influence extends to climate regulation through participation in the local hydrologic cycle. Moreover, inland waterways enrich Guam’s cultural heritage and provide recreational opportunities, underscoring their immense value to the island and its people.
Key Vocabulary
- Contaminant
- Erosion
- Evaporation
- Filtration
- Groundwater
- Hydrologic cycle
- Precipitation
- Purification
- Riparian zone
Learning Objectives
- Students will describe how riparian zones, including vegetation and soil, contribute to the filtration of water by preventing erosion and absorbing excess nutrients and contaminants.
- Students will define the hydrologic cycle and describe the processes of evaporation, condensation, precipitation, and infiltration.
- Students will assess how water moves through different stages of the hydrologic cycle, considering the unique role of groundwater and coastal aquifers on Guam.
Next Generation Science Standards Alignment
ESS2.C: The Roles of Water in Earth’s Surface Processes: The students will learn that inland waterways contribute to water filtration and the hydrologic cycle.
Water Filtration
Guam’s freshwater resources, primarily sourced from reservoirs and groundwater, are limited in quantity. Nevertheless, the island’s inland waterways, though relatively small, play a crucial role in water filtration. Like other regions, these waterways undergo a natural purification process. Vegetation thriving along the riverbanks, known as riparian zones, acts as a living filter, preventing soil erosion and capturing sediments. The intricate root systems of these plants effectively absorb excess nutrients and harmful contaminants, enhancing water quality. Additionally, the underlying geology, composed of rocks, gravel, and sand, contributes to the filtration process by trapping impurities and allowing cleaner water to seep through.
Guam, like other nations, has a water filtration system for drinking water. The filtration system mainly focuses on treating groundwater due to the islands geology and the limited availability of surface water sources. The Guam Waterworks Authority (GWA) is responsible for managing and distributing water to the island’s residents.
Image: Hydrologic Cycle in all areas of an ecosystem
Hydrologic Cycle
The hydrologic cycle is the natural process that shows continuous movement of water on, above, or below the Earth’s surface. Also known as the water cycle, it follows the movement of water around the earth. Water evaporates from bodies of water and into the atmosphere. The water vapor condenses in clouds and falls back to the earth as precipitation, or rain. The precipitation then enters the bodies of water directly or is soaked into the ground where it becomes groundwater. The water that enters the bodies of water is called surface water and is the place where evaporation starts the cycle over again. Inland waterways, like lakes, rivers and streams, are the key starting point for the hydrologic cycle.
Since Guam is a tropical island, it experiences high levels of precipitation throughout the year and particularly during rainy seasons. With its lack of surface waters Guam’s hydrologic cycle is a bit different than that of nations with an abundance of lakes, streams, and rivers. A majority of freshwater is found underground in aquifers and water is released into coastal aquifers. Once the water reaches the ocean the hydrological cycle follows the same pattern as the rest of the world.
Summary
Guam’s inland waterways are crucial to the island’s ecological health, biodiversity, and water quality. These waterways serve as vital habitats for wildlife, act as natural filters by trapping sediments and pollutants, and support the island’s hydrologic cycle by replenishing groundwater and surface water supplies. The riparian zones and underlying geology play key roles in improving water quality, while the hydrologic cycle helps regulate Guam’s freshwater resources, which are primarily sourced from groundwater due to the limited availability of surface water. Understanding these natural systems is essential for effective water resource management, as demonstrated by the efforts of the Guam Waterworks Authority to ensure a sustainable water supply for the island’s residents.
The Changing Climate
Background
Climate change poses significant threats to Guam’s inland waterways. Altering precipitation patterns, characterized by more intense rainfall events and extended dry periods, directly impact freshwater availability and river flow. Rising temperatures exacerbate these challenges, accelerating evaporation and reducing water levels. Consequently, water quality deteriorates as warmer waters hold less oxygen, creating unfavorable conditions for aquatic life. Extreme weather events, such as droughts and typhoons, further disrupt the delicate balance of these ecosystems, leading to habitat loss, erosion, and changes in species distribution. These cumulative impacts jeopardize the health and integrity of Guam’s inland waterways and the biodiversity they support.
Key Vocabulary
- Agriculture
- Conservation
- Drought
- Precipitation
Learning Objectives
- Students will learn how intense rainfall events impact ecosystems through flooding, habitat loss, and erosion, and how these changes affect the biodiversity and water quality of Guam’s inland waterways.
- Students will examine how prolonged periods of drought, worsened by climate change, reduce water availability and affect agriculture, water supply, and aquatic ecosystems on Guam.
Next Generation Science Standards Alignment
ESS2.C: The Roles of Water in Earth’s Surface Processes: The students will learn that heavy rainfall impacts ecosystems through flooding and habitat loss.
ESS2.D: Weather and Climate: The students will learn that climate patterns affect the water cycle and can lead to extreme weather events such as floods and droughts.
Effects of Precipitation
Intensified precipitation patterns due to climate change pose significant threats to Guam’s inland waterways and the surrounding communities. Heavy rainfall events, characterized by higher intensity and frequency, can overwhelm the capacity of these waterways, leading to severe flooding. This excess water can cause rapid erosion, destabilizing riverbanks and increasing sedimentation in the water bodies. Such conditions can disrupt aquatic ecosystems, destroying habitats and altering fish populations. Moreover, flooding can inundate agricultural lands, causing substantial crop damage and economic losses to farmers. The infrastructure in flood-prone areas is also at risk, with roads, bridges, and buildings susceptible to damage or destruction. Beyond the immediate impacts, excessive rainfall can contribute to long-term changes in water quality by increasing nutrient and sediment loads, affecting aquatic life and drinking water sources
Droughts
Droughts, characterized by prolonged periods of deficient precipitation, pose significant challenges to Guam’s water resources, agriculture, and ecosystems. Climate change, including the influence of El Niño and La Niña weather patterns, has contributed to increased frequency and severity of droughts. Reduced rainfall diminishes water levels in rivers, streams, and reservoirs, straining water supplies for both human consumption and ecological needs. Agricultural productivity declines as crops wither under the relentless sun and lack of moisture. Moreover, droughts can lead to increased wildfires, soil erosion, and the decline of aquatic ecosystems. To mitigate the impacts of these water shortages, implementing water conservation measures, such as efficient irrigation practices, rainwater harvesting, and public awareness campaigns, becomes crucial for ensuring the sustainability of Guam’s water resources.
Shipping & Navigation
Key Vocabulary
- Mandate
- Pollution
- Safeguard
- Seaworthy
Learning Objectives
- Students will learn about the local significance of Guam’s inland waterways, including their role in recreation, small-scale boating, and their connection to the broader marine ecosystem.
- Students will understand the importance of pollution prevention for protecting Guam’s freshwater resources, with a focus on the role of the Guam Environmental Protection Agency and local mandates like the Clean Water Act.
- Students will explore the regulations set by the Port Authority of Guam for recreational boating, focusing on safety, responsible boating practices, and the importance of minimizing environmental impact.
Next Generation Science Standards Alignment
ETS1.B: Developing Possible Solutions: The students will learn that the Port Authority of Guam has regulations in place to prevent potential pollution issues caused by recreational vessels.
ETS2.A: Interdependence of Science, Engineering, and Technology: The students will learn that collaborations between scientific research, engineering design, and addressing environmental challenges in inland waterways underscore the importance of integrating all three to sustainably manage and protect freshwater ecosystems.
Recreation Crafts
The Port Authority of Guam holds primary responsibility for regulating recreational boating activities within its territorial waters. To ensure safe and responsible boating practices, all recreational vessels must comply with specific standards within Guam’s harbors. These regulations encompass a range of essential requirements, including maintaining vessel seaworthiness, exercising caution when passing larger vessels, and utilizing navigation equipment to accurately determine and maintain vessel position. Adherence to these rules is paramount for safeguarding both human life and the marine environment. By enforcing these standards, the Port Authority aims to prevent accidents, minimize pollution, and promote the sustainable enjoyment of Guam’s waterways.
Pollution Prevention
Guam has a Water Pollution Control Program dedicated to protecting freshwater on Guam from pollution. Local mandates like The Water Pollution and Control Commission (1960’s) were established to manage and protect Guam’s freshwater. In 1973 the commission’s duties were passed to the Guam Environmental Protection Agency, who followed the mandates outlined by the Clean Water Act. The EPA’s Control Program is divided into two sections, The Community Wastewater Section, and the Individual Wastewater Section. Federal and Local mandates are crucial to the environment and its livelihood. Controlling point and non-point sources of pollution is the only way to protect fresh inland water.
PowerPoint: Inland Waterways
Summary
Guam’s inland waterways differ significantly from the vast expanses of the open ocean, as they do not serve as major shipping or navigation channels. Nonetheless, these water bodies hold substantial local importance. They provide recreational opportunities, such as fishing, and are utilized by small vessels. It is imperative to recognize the interconnectedness of these waterways with the larger marine ecosystem. To safeguard the delicate balance of aquatic life, pollution prevention and responsible boating practices are essential. Minimizing disturbances to these habitats is crucial for preserving their ecological integrity and ensuring the long-term health of Guam’s aquatic resources.
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