Summary of Lecture on Drainage Basin Hydrology
This lecture covered the basic concepts of drainage basin hydrology, focusing on the hydrological cycle within a drainage basin, which is described as an open system with defined inputs, flows, storages, and outputs. Emphasis was placed on understanding the pathways and processes involved in moving and storing water within a drainage basin, including precipitation, interception, infiltration, percolation, and channel storage. The discussion highlighted how these components interact to affect the hydrology of the basin.
Key Points from the Lecture
Drainage Basin Hydrology
- Definition: A drainage basin is an area where water from rain and other sources accumulates and drains off into a common outlet, such as a river.
- Open System: It interacts continuously with the environment and includes inputs and outputs.
Components of Drainage Basin Hydrology
- Inputs: The primary input is precipitation which can be in various forms like rain, snow, dew, etc.
- Outputs: Mainly river runoff and evapotranspiration.
- Flows or Pathways: Includes processes like interception loss, infiltration, percolation, true flow, and base flow.
- Storages: Various forms of water storage within the basin, including interception, soil moisture, groundwater, and channel storage.
Detailed Processes and Terms
- Interception Loss: Water caught by vegetation; not all the intercepted water reaches the ground.
- Infiltration: The process by which water on the ground surface enters the soil.
- Infiltration Capacity: Maximum rate at which soil can absorb water.
- Factors Affecting Infiltration: Includes soil permeability, vegetation cover, and rainfall intensity.
- Percolation: Movement of water through soil and rock layers beneath the ground surface.
- Overland Flow: Water that flows over the land surface.
- Hortonian Overland Flow: Occurs when rainfall intensity exceeds the infiltration rate.
- Saturated Overland Flow: Happens when the soil is completely saturated and additional rainfall cannot infiltrate.
Types of Water Storage
- Interception Storage: Water stored on leaves and stems of plants.
- Soil Moisture Storage: Water held in the soil in the unsaturated zone.
- Groundwater Storage: Water stored in the saturated zones below the soil surface.
Outputs
- River Runoff: Water that flows into rivers and eventually into seas.
- Evapotranspiration: Combined effect of evaporation and transpiration from the Earth’s surface and plant leaves.
Exam Requirements
- Understand the interactions of the various parts that make up the drainage basin hydrology.
- Topics often included in essay questions and data response exercises.
This lecture gives a foundation for understanding how water is managed in a drainage basin and the importance of different hydrological processes in determining the movement and storage of water. Knowing these processes is crucial to understanding broader ecological, environmental, and geographical concepts.