4-1    Hydrologic cycle:

1. Circulation of water among atmosphere, hydrosphere, and solid earth.

2. Infiltration: downward movement of water in soil.

3. Runoff: running water at the surface due to gravitational forces.

4. Evaporation: liquid water changes into water vapor.

5. Transpiration: release of water by plants to atmosphere. Fig. 4.2.

4-2    Running water:

1. Water flows under hydraulic gradient, which is (h₁-h₂)/L. thus, the higher the gradient, the higher the velocity.

2. Discharge: amount of water flowing per unit time.

3. Longitudinal profile of a stream. Fig. 4.5.

4-3    Work of stream: transportation along path:

1. Near the head: erosion. Gradient high, flow faster, water has higher energy, thus, able to undercut the channel.

2. Near the mouth: deposition. Gradient low, flow slower, energy low, previously carried particles too heavy to be carried anymore, thus, deposit.

3. Transportation: three ways of carrying load:

   • by dissolution

   • by suspension

   • by rolling

   Competence vs. capacity: the former refers to the maximum size of particles, controlled by speed. While the latter refers to the maximum load of carry, determined by discharge. Weh speed increase by 2, the competence increases by 4.

4. Base level of a stream: the lowest level of a stream can erode. Upper stream erosion: Fig 4.6. Erosion of river channel in upstream direction until base level is reached.

5. Deposition:

   1. Sorting: a process to separate particels based on size.

      • Well sorted: uniform particle size distribution.

      • Poorly sorted.

   2. Alluvium: well sorted channel deposits.

   3. Delta: deposits at the mouth to an open water body, e.g. sea.

   4. Formation of delta: sudden reduce in speed caused massive deposits.

   5. Distributaries: small river channel derived from main channel.

   6. Natural levees: caused by flood period deposit. When flow over bank, speed reduced, particles deposit.

   7. Back swamp: results due to poor drainage. Fig 4.11.

   8. Flood plains:

4-4    Stream Valley:

1. V-shape: narrow, indicating downcutting as represented by rapids and water falls. Where? Near the head of the stream

2. Wide valley: 

   

   • Side erosion

   • Meanders: rivers that have wider curves on their flow path. Where? Near the end of the stream.

3. Floodplains: Fig. 4.11. Due to side-to-side cutting, the river channel creates a wider area, where there is a flood during peak time.

   • Could be erosional or depositional.

4. Oxbow lakes: as meander gets curvy, eventually river erodes the neck and creaste a new short cut - called cutoff, and the abandoned channel - oxbow lake.

4-5    Stages of valley development:

1. Youth: characterized by V-shape valleys, down-cutting, rapids, waterfalls predominant.

2. maturity: down-cutting power decreases, lateral erosion increases, stream gets curvy.

3. Old age: wider meander belt, extensive oxbow lakes and natural levees.

4. Rejuvenated: meanders become deeper- called entrenched meander, e.g. Grand Canyon.

Terraces: flat surface produced from previous flood plains.

Entrenched meanders and terraces indicate upward movement of the Earth.

4-6    Drainage patterns:

1. Drainage basin: the area t\where water drains to stream.

2. Divide: imaginary line, high in elevation, separate drainage basins. Fig 4.19.

3. Drainage patterns: Fig. 4.20.

   1. Dendritic: treelike

   2. Radial: flow from center.

   3. Rectangular:

   4. Trellis:

Controlled by rock types and structure of the bedrock.

4-7    Groundwater:

Water existing beneath the surface. Fig 4.22.

1. Saturated: solid & liquid coexist.

2. Unsaturated: solid + liquid + air.

3. Water table: where soil become saturated.

4. Aquifer: soil or rock that can store and transmit water.

5. Aquicludes: store water but not transmit water.

6. Permeability: tells how well the rock or soil can transmit water. Thus, aquifer has high permeability while aquicludes have low permeability.

7. Porosity: ratio of void space to total volume.

8. High porosity does not mean high permeability. Clay has high porosity but low permeability. That is why clay can store water but not transmit water.

9. Spring: water flow out from ground laterally. Why? Ground surface intercept water table. Fig. 4.23.

10. Hot spring: due to higher geothermal gradient. Normally, T increases 2 degrees per 100 m.

11. Geysers: intermittent hot springs. Fig. 4.25. As depth increase, boiling T increases, as water heated, it expands, when portion of the expanded water flow out, pressure gets reduced. As P decreases and T remains the same, water boils, causing geyser eruption.

4-8    Wells:

1. Cone of depression:

2. If extensive pumping, cone of depression gets bigger, may cause some wells to dry out.

3. Flowing artesian well: water flow out automatically. Why? water under pressure but sealed on top due to overlying aquiclude, which create pressure surface. If the pressure surface is higher than the ground surface, a flowing artesian condition forms. Fig. 4.27. 

4-9    Problems with groundwater:

1. Renewable vs. nonrenewable: depending on the rate of recharge and the rate of withdrawal. If the latter is greater than the former, water table will decline. So we need groundwater conservation.

2. Land subsidence: when water removed, pore claps, cause volume reduction. Fig. 4.29.

3. Groundwater contamination: due to 

• leachate from landfill.

• leak from UST (underground storage tank).

• fertilizer and pesticide application.

4-10    Water in carbonate terrain.

• Caverns: carbonate dissolved by water underground. At surface water is saturated with CO₂, thus, the water is a little acidic and has dissolving power. As T changes in caverns, precipitation happens.

• Stalactite vs. stalagmite, column forms when they joint together.

• Karst topography: characterized by sinkhole created by dissolution of carbonate rocks. Bedrock: carbonate, climate: plenty of rain, underground connection.

Homework:

• Read chapter summary on p.119.

• Use your own word to explain the key terms on page 120.

• Answer the review questions.