Water Resources and Rivers

Water Resources and Rivers

Overview of Content

  • Readings: Interlude F and Chapter 14

  • Outline of Topics:

    • Landscapes Terminology

    • Introduction to Water

    • Origin of Running Water

    • Stream Flow Dynamics

    • Stream Erosion

    • Stream Types and Deposits

    • Flooding

    • Lecture Review

Landscapes

  • Definition: Character and shape of land surface in a region.

  • Landforms: Individual shapes like valleys, cliffs, beaches that compose landscapes.

Topography

  • Definition: Variation in land surface elevation.

  • Representation: Shown on topographic or shaded relief maps.

  • Erosion Resistance: The resistance of substrate to erosion determines topography.

Erosion and Deposition

  • Erosion: Removal of the Earth’s surface due to agents such as water, ice, and air.

  • Deposition: Accumulation of sediment transported by erosional agents.

  • Factors Influencing Landscape Development:

    • Agents of erosion

    • Topographic relief

    • Climate

    • Substrate composition

    • Biological activity

    • Time

Introduction to Water

  • Primary Source:

    • 90% from the Colorado River; originates from Rocky Mountains, flows to Lake Mead.

    • 40% of water is used indoors and then returned.

  • Groundwater: Comprises 10% of water resources.

Drainage Systems

  • Surface Runoff: Water flowing on Earth's surface including rain and melting snow.

  • Channel Formation: Resulting from water interaction with substrate, leading to differentiation into various channels.

  • Drainage Basin: A network that collects water draining into a trunk stream, separated by drainage divides.

Stream Types and Dynamics

  • Stream Flow Definition: The volume of water passing a point, varying with time and weather (ft3/sft^3/s or m3/sm^3/s).

  • Gradient: Slope of stream channel (elevation change over distance).

  • Velocity: Varies across channels with highest at the center (v=racdtv = rac{d}{t}).

  • Load Types:

    • Dissolved Load: Ions from weathering

    • Suspended Load: Fine particles (silt, clay)

    • Bed Load: Coarse particles that move along the bottom (saltation).

Stream Erosion

  • Mechanism: Flowing water converts potential to kinetic energy; higher energy during floods leads to increased erosion.

  • Erosion Techniques: Streams break, lift, remove, and dissolve materials.

  • Stream Piracy: The phenomenon where a stream captures another by headward erosion.

Meandering vs. Braided Streams

  • Meandering Streams: Flow in winding patterns; erosion on outer banks and deposition on inner banks.

  • Braided Streams: Multiple channels with interlaced flows, common in high sediment conditions or in front of glaciers.

Alluvium and Flooding

  • Alluvial Fans: Formed at the base of mountains due to rapid sediment dropping as streams lose energy.

  • Floods: Occur when discharge rises beyond bank capacity, causing scouring of surrounding areas, influenced by heavy rains or dam failures.

Key Terminology

  • Erosional Landforms: Features resulting from material removal.

  • Floodplain: Area that typically experiences flooding when rivers swell, defined by river stages: normal, bankfull, and flood stage.

  • Natural Levees: Elevated areas parallel to stream channels that help contain floods.

Conclusion and Review Questions

  • Key concepts to focus on:

    • Hydrologic cycle

    • Different drainage basin types

    • Stream dynamics and flow terminology

    • Flooding implications

  • Suggested readings and review materials to solidify understanding of the water resources and river systems.