Explanation: The established definition of water level concerns the elevation of the water's free surface relative to a vertical datum, not its flow rate. Flow rate is a distinct hydrological parameter.

Explanation: The terms 'gauge height' and 'stage' are commonly used synonyms or closely related terms for water level, referring to the elevation of the water surface relative to a datum.

Explanation: A vertical datum serves as a reference point for measuring vertical elevations, including water levels, not for determining the horizontal dimensions of a water body.

Explanation: A 'Water level (device)' is described as an instrument used to establish a local horizontal reference, distinct from the 'water level' concept itself, which is the measured elevation.

Explanation: A reference water level is established as a consistent baseline or benchmark against which other water level measurements are made or compared.

Explanation: In hydrology, 'Stage' is synonymous with water level or gauge height, referring to the elevation of the water surface relative to a datum, not the speed of flow.

Explanation: The term 'gauge height' specifically implies that the measurement is taken using a gauge or instrument, indicating a practical, instrument-based measurement.

Explanation: The definition of water level applies broadly to various water bodies, including seas, streams, lakes, and reservoirs, encompassing both natural and artificial containment.

Explanation: Water level is fundamentally defined as the elevation of the free surface of a body of water (such as a sea, stream, lake, or reservoir) measured with respect to a specific vertical datum.

Explanation: The terms 'gauge height' and 'stage' are explicitly identified as synonyms or closely related terms for 'water level' within the provided context.

Explanation: A vertical datum serves as a standardized baseline or reference point used to measure elevations, including the elevation of the water surface.

Explanation: A reference water level is crucial as it provides a consistent and stable benchmark for all subsequent measurements and comparisons of water elevation.

Explanation: In hydrology, 'stage' is a technical term that denotes the elevation of the water surface relative to a specified datum, essentially synonymous with water level or gauge height.

Explanation: The 'free surface' denotes the boundary of a body of liquid that is exposed to the atmosphere or another non-liquid medium, and it is this surface whose elevation is measured as water level.

Explanation: The definition of water level is applicable to a range of water bodies, including seas, streams, lakes, and reservoirs, as indicated in the source material.

Explanation: The term 'flood stage' denotes the specific water level at which a river or stream commences to overflow its natural confines onto adjacent land.

Explanation: Hydraulic head is indeed a concept in fluid mechanics that quantifies the total mechanical energy of water per unit weight, often expressed as an equivalent height or pressure.

Explanation: 'Liquid level' is a general term applicable to any liquid, whereas 'water level' is specific to water. The definition of water level applies to various bodies of water, not just rivers.

Explanation: Sea level refers to the average height of the ocean's surface relative to a vertical datum, serving as a reference point for elevation, not its average depth.

Explanation: 'Flood stage' signifies the specific water level at which a river or stream begins to overflow its banks, marking the onset of flooding.

Explanation: Hydraulic head is a concept in fluid mechanics that represents the total mechanical energy of water per unit weight, frequently expressed as a height, and is directly related to water level.

Explanation: 'Water level' is a specific term denoting the elevation of water, whereas 'liquid level' is a more general term applicable to any liquid substance.

Explanation: Sea level is significant globally as a fundamental reference point for measuring land elevations and is also a key indicator for monitoring climate change impacts.

Explanation: Water level, representing the elevation of the water surface, is a key factor used in the calculation and understanding of hydraulic head, which quantifies the energy of the water.

Explanation: ISO 772:1996 provides general definitions and symbols for hydrometric determinations, not specific measurement protocols for individual rivers like the Nile.

Explanation: The primary function of a stream gauge is to measure the water level or flow rate of a stream or river, not its temperature.

Explanation: A tide gauge is specifically designed to measure the rise and fall of sea level due to tides, typically at coastal marine locations.

Explanation: A level sensor is a general term for devices that detect or measure the level of various substances, most commonly liquids, and is not limited to atmospheric pressure measurement.

Explanation: The ISO 772:1996 standard is dedicated to providing definitions and symbols pertinent to hydrometric determinations, which is the measurement of water.

Explanation: A stream gauge is an instrument primarily designed to measure and record the water level (stage) or flow rate of a stream or river.

Explanation: A tide gauge is specifically designed to measure the variations in sea level caused by tides, typically deployed at coastal marine locations.

Explanation: Level sensors constitute a broad category of devices designed to detect or measure the level of various substances, including liquids like water, across diverse applications.

Explanation: While both measure water levels, tide gauges are specialized for recording sea level fluctuations from tides, whereas stream gauges monitor water levels in rivers and streams, influenced by factors like flow and precipitation.

Explanation: In the absence of external forces like wind, the free surface of large water bodies naturally conforms to an equigeopotential surface, which is a surface of constant gravitational potential.

Explanation: An equigeopotential surface is characterized by having the same gravitational potential energy at every point, not necessarily the point of maximum gravitational pull.

Explanation: The provided text explicitly mentions wind as an external force that can affect water levels over long distances.

Explanation: The cited Merriam Webster definition indicates that 'level' in this context means conforming to the curvature of the Earth's liquid surfaces, not a flat plane.

Explanation: Conforming to an equigeopotential surface means the water level follows the Earth's curvature and gravitational field, not that it forms a perfectly flat plane.

Explanation: The Merriam Webster definition cited implies that a water level surface conforms to the Earth's curvature, not that it must be a perfectly flat plane.

Explanation: When external influences are absent, water levels over long distances naturally align with an equigeopotential surface, reflecting the influence of Earth's gravity and curvature.

Explanation: Wind is explicitly cited as an external force that can influence water levels over extended distances.

Explanation: The Merriam Webster definition indicates that 'level' in this context means conforming to the curvature of the Earth's liquid surfaces, rather than being a flat plane.

Explanation: This statement implies that water naturally seeks a level surface that is influenced by the Earth's gravitational field and its overall shape, rather than being a simple flat plane.

Explanation: The 'See also' section typically includes both related devices and related concepts to aid reader navigation and understanding.

Explanation: Authority control sections link to standardized identifiers in various databases, ensuring consistent identification and retrieval of the subject 'Water level' across different information systems.

Explanation: The GND (Gemeinsame Normdatei) is the German National Library's standard authority file, not originating from the United States.

Explanation: The input data does not specify the update date for the single-source template; it only indicates the template's existence and purpose.

Explanation: A stub notice indicates that an article is brief and requires expansion, encouraging further contributions rather than signifying completeness.

Explanation: The stub notice identifies the 'Water level' article as belonging to the field of hydrology, not geology.

Explanation: The article distinguishes between the concept of 'water level,' which is the measured elevation of the water surface relative to a datum, and a 'water level (device),' which is an instrument used to establish a local horizontal reference line.

Explanation: The provided source material lists authority control links for the Library of Congress (United States), the National Diet Library (Japan), and the Israel National Library, but not the Bibliothèque nationale de France.

Explanation: Authority control databases provide standardized identifiers and names, ensuring consistency and aiding in the accurate retrieval and cataloging of the subject 'Water level' across various systems.