Hydrology

Hydrology of Creek System

General Overview

  • Transect three represents a creek system connecting freshwater drainage and the lagoon hydrology of Aqua Hedionda.

  • Key observations include:

    • Fast-moving section of the creek.

    • Main bed material consisting of mud.

    • Gentle slope observed in the creek.

Physical Measurements

  • Width: 240 centimeters.

  • Depth: 64 centimeters.

  • Slope: Gentle, indicating a stable flow regime.

Erosion and Human Impact

  • Erosion: Moderate erosion noted, indicating active interaction between flowing runoff and channel walls.

  • Human Impact: Evidence of human disturbance was observed, such as:

    • A plastic chair located farther downstream in the creek bed.

Biological Activity

  • Various forms of biological life observed, indicating ecosystem health:

    • Vegetation: Presence of pickleweed plants.

    • Fauna:

    • Frog larva identified, serving as indicators of aquatic ecosystem health.

    • Sightings of an egret, indicating the availability of habitat and feeding opportunities.

  • The presence of these life forms suggests that despite runoff influence, the creek supports biological productivity.

Water Quality Measurements

  • Temperature: 23 degrees Celsius, suitable for most aquatic organisms.

  • Turbidity: Measured at approximately 20-30 JTU, typical for a fast-flowing creek, indicating some suspended particles but not detrimental to the ecosystem.

  • Dissolved Oxygen (DO): Initially low at about 2 parts per million (ppm); readings ranged from 0-5 ppm.

    • Low DO levels can signify stress for aquatic life since most species require higher oxygen concentrations.

Nutrient Measurements

  • Nitrate: Data from colleagues indicated a mean level of 5 ppm, with initial tests failing to yield results.

  • Phosphate: Measured at 2 ppm.

  • pH Level: Determined to be 8, slightly alkaline, yet within a survivable range for aquatic species.

  • Nutrient Pollution Assessment:

    • The low concentrations of nitrates and phosphates suggest low levels of nutrient pollution, which is favorable since high nutrient loads are typically a concern in urban runoff.

Ecological Assessment

  • The overall assessment of the creek indicates a relatively healthy aquatic system:

    • Despite low dissolved oxygen, the presence of frog larva, pickleweed, and egrets reflects moderate ecological function and sustainability.

    • The flowing nature of the creek likely supports oxygen exchange and minimizes bacterial buildup.

Potential Impacts and Implications

  • Oxygen Levels: Low dissolved oxygen may become a concern during warmer temperatures or reduced flow periods, leading to potential stress on aquatic species.

  • Ecological Resilience: The creek shows signs of resilience, supporting aquatic life that can tolerate lower oxygen levels and offering essential habitat resources. This indicates a functioning ecosystem despite some human influence and environmental stressors.

Conclusion

  • The hydrology of Transect three suggests a vital freshwater contribution to the overall health of the Aqua Hedionda lagoon system, integrating both ecological and chemical parameters that highlight the creek's role in the local hydrological network.

  • While the observations point to a relatively clean ecosystem, ongoing monitoring and management may be necessary to ensure it remains resilient against anthropogenic impacts and natural fluctuations.