To determine the correct answer for what stream discharge is, we need to understand the definitions and concepts related to this term. Let's analyze each given option in detail:
1. The area of land that drains water to a stream gage:
- This definition refers to the drainage basin or watershed area. This is the land area where precipitation collects and drains off into a common outlet, like a stream gage. This is not the correct definition of stream discharge.
2. The volume of water exiting a watershed:
- This description is close but not entirely accurate. While stream discharge does involve the volume of water, it is specific to the flow at a particular point in time rather than the total volume exiting an entire watershed.
3. The height of the water surface above a reference elevation:
- This definition pertains to stage or gage height, which is the elevation of the water surface above a chosen reference point, usually concerning stream flow monitoring. This is not the definition of stream discharge.
4. The volume of flow passing a specified point in a given amount of time:
- This accurately describes stream discharge. Stream discharge is the volume of water moving through a cross-section of the stream in a specified time period, typically expressed in cubic feet per second (cfs) or cubic meters per second (cms).
Based on the analysis above, the correct answer is:
◇ the volume of flow passing a specified point in a given amount of time.
To summarize, stream discharge is the measurement of the volume of water passing a certain point in the stream over a defined time period. This measurement is crucial in hydrology for understanding the dynamics and health of water bodies.
