What does a watershed water budget account for?

What does a watershed water budget account for?

• A. The balance of water inputs (precipitation, inflow) and outputs (evapotranspiration, runoff, discharge) and changes in storage within a drainage basin.
• B. Only rainfall and evaporation.
• C. Only runoff and discharge.
• D. Only evaporation.

Answer: (A)

A watershed water budget tracks water as a simple balance inside a drainage basin over a period of time. It includes three pieces: inputs, outputs, and changes in storage. Inputs are what bring water into the basin—precipitation that falls within the watershed and inflow from upstream areas. Outputs are what take water out—evapotranspiration from land and water surfaces, runoff that moves across the surface within the basin, and discharge leaving the basin at its outlet. The storage term accounts for water stored or released from within the basin, such as soil moisture, groundwater, and surface water in lakes or reservoirs, which can increase or decrease over time. So the budget is essentially water in equals water out plus any change in storage (or, equivalently, inputs minus outputs equals the change in storage). This is why the option that includes all these components is the correct one. The other choices only consider a subset of components and miss either inputs, either outputs, or storage changes.

A watershed water budget tracks water as a simple balance inside a drainage basin over a period of time. It includes three pieces: inputs, outputs, and changes in storage.

Inputs are what bring water into the basin—precipitation that falls within the watershed and inflow from upstream areas. Outputs are what take water out—evapotranspiration from land and water surfaces, runoff that moves across the surface within the basin, and discharge leaving the basin at its outlet. The storage term accounts for water stored or released from within the basin, such as soil moisture, groundwater, and surface water in lakes or reservoirs, which can increase or decrease over time.

So the budget is essentially water in equals water out plus any change in storage (or, equivalently, inputs minus outputs equals the change in storage). This is why the option that includes all these components is the correct one. The other choices only consider a subset of components and miss either inputs, either outputs, or storage changes.