Definition
The head of a stream is the uppermost point of origin of a watercourse — the farthest upstream location from which the stream flows. Where a stream has multiple branches or forks converging to form the main channel, the head is identified by reference to the branch that contributes the greatest volume of water, making it the principal or dominant fork rather than any secondary tributary.
This definition carries practical weight in property law, water rights, and boundary disputes, where the precise location of a stream's head may determine the extent of a riparian owner's land, the scope of a water appropriation, or the terminal point of a described boundary line.
Common Language
Modern common usage (Wiktionary): The "head" of a river or stream refers informally to its source or origin — the place where it begins, often a spring, lake, or confluence of smaller waters.
Historical common usage (Webster's 1913): Webster's defines "head" in a geographical sense as the source of a stream or river; the place where it rises.
Common usage and legal usage largely align on the basic concept of origin. The legal definition adds a specific rule of determination that everyday usage does not: when a stream branches, the head is not simply whichever fork is most remote or most prominent on a map, but the fork that supplies the greatest volume of water. This volume-based test is a legal resolution to an ambiguity that ordinary language leaves unaddressed.
Core Elements
Where a stream has a single, unambiguous source, the head is that source. Where branches exist, courts have applied the following test:
1. Identify all forks or branches that may constitute a candidate for the main channel.
2. Assess the relative volume of water furnished by each branch.
3. The branch supplying the dominant volume is treated as the main fork, and the head of that branch is the head of the stream.
This volume-based standard resolves the most common boundary and water-rights disputes involving multi-branched watercourses.
Why It Matters in Research
The practical significance of this term is concentrated in two research contexts: riparian boundary descriptions and prior appropriation water rights.
In boundary law, deeds and government surveys frequently describe land as running "to the head of" a named stream. When the stream has multiple forks, identifying the correct head controls the outer limit of the grant. Researchers working with historical land patents, federal survey records, or state boundary instruments must understand that the legal answer to which fork is the "head" may differ from what appears on a topographic map — the legally controlling fork is determined by water volume, not by geographic remoteness or cartographic convention.
In western water law, the point of diversion and the extent of an appropriation can hinge on where a stream legally begins. Historical filings and adjudication records may describe rights by reference to the head of a stream without specifying the volume-based analysis that would be needed to locate that point when branches exist.
Researchers should also note that this is an area where documentary evidence (historical survey notes, stream gauge records, hydrological reports) may be as important as legal authority. The factual question of which branch carries the greater volume was and remains a matter of proof, not legal presumption.
Historical Dictionary Support
Bouvier's Law Dictionary provides a terse but useful entry, citing a single decision for the proposition that the main fork is whichever branch furnishes the main volume of water. Bouvier does not elaborate on evidentiary standards, seasonal variation in volume, or what happens when flows are substantially equal across branches — gaps that limit the entry's utility for complex disputes. The single southwestern reporter citation (64 S.W. 501) reflects the term's primary practical importance in arid and semi-arid jurisdictions where precise stream identification governs scarce water allocation. Researchers should not treat Bouvier's silence on edge cases as indicating settled law on those points.
Jurisdictional Note
The volume-based test for identifying the main fork appears most prominently in western states operating under prior appropriation systems, where precise stream identification has economic significance. Eastern riparian jurisdictions have encountered the issue less frequently in reported decisions. Researchers working in any jurisdiction should check whether state water codes or survey statutes supply their own definition before relying on the common-law volume test.