Scope of hydrology as a discipline Hydrology is best described as the science dealing with which category of water on and below the Earth’s surface?

Introduction / Context:
Hydrology investigates the occurrence, distribution, movement, and quality of water throughout the hydrologic cycle. It encompasses meteorological inputs, surface processes, subsurface storage and flow, as well as interactions with landforms and ecosystems.

Given Data / Assumptions:

• The term “hydrology” is used in the standard engineering sense (surface-water and groundwater hydrology).
• Oceanography is treated as a related but distinct discipline focusing on ocean waters.

Concept / Approach:

Hydrology spans precipitation, interception, infiltration, runoff generation, streamflow, lake and reservoir processes, vadose-zone flow, groundwater recharge, aquifer flow, and discharge to springs or streams. Floods and droughts are special regimes within this broad field, not the entirety of it.

Step-by-Step Solution:

Verification / Alternative check:

Standard engineering hydrology texts define the discipline as the study of water over and beneath the Earth’s surface, inclusive of rainfall-runoff transformation and groundwater mechanics.

Why Other Options Are Wrong:

• Rain water only / river water only / flood water only: Each is a subset of hydrologic phenomena.
• Sea water only: Oceanography domain, not the primary scope of engineering hydrology.

Common Pitfalls:

• Equating hydrology solely with streamflow measurement; groundwater and near-surface processes are equally essential.

Final Answer:

Surface water and underground (ground) water.