SCHWAB, C.J.
In this declaratory judgment proceeding, which is equitable in nature, plaintiffs are three Washington County farmers who hold water permits entitling them to appropriate a set amount of water for irrigation. Defendants are the State Engineer and District Watermaster who issue such permits and regulate their use. Defendants have demanded that plaintiffs repair or reconstruct a dam in order to continue to appropriate water under their permits. Plaintiffs, arguing they have no obligation to do so, appeal from an adverse judgment in the circuit court.
In order to discuss the merits of this dispute, it is first necessary to describe the topography involved. The diagram on the following page may facilitate this description.
In the area here involved West Dairy Creek flows generally west to east, i.e., originating west of point A and terminating east of point E where it [28]*28empties into the Tualatin Biver. The parties agree that: (1) for about the first 20 or 30 years of this century the creek flowed from A to B to C to D to E; (2) now the creek follows its old course between points A and B, and between points D and E; and (3) now at point B the water in the creek divides, with most of it following the route of B to Gr to D, and the rest following the part of its original course of B to C to D.
Plaintiffs refer to the stretch from B to Gr to D as an unnamed channel that forks from West Dairy Creek at point B and rejoins it at point D. As best we understand them, defendants refer to the stretch from F to G- to D as an unnamed channel, and the stretch between B and Gr as a diversion ditch. For purposes of discussion, however, these different characterizations are easy to resolve, since all parties seem to agree that the stretch between F and Gr is almost always a dry bed. Thus, as far as actually tracing the usual flow of the water, we believe plaintiffs’ description is more accurate, and will use their terminology, i.e., refer to the B-Gr-D stretch as the unnamed channel.
There are two dams on the unnamed channel; Dam #1 is located generally east of point B and Dam #2 is located generally west of point D.
Dam #2 was constructed and is maintained by plaintiffs under water permits that enable them to create a reservoir north of that dam. The plaintiffs draw water from this reservoir to use for irrigation. Plaintiffs’ property lies on both sides of the unnamed channel, with most of it being north thereof. Persons other than plaintiffs also own property along the unnamed channel. The channel flows through these persons’ property before reaching plaintiffs’ property.
Dam #1 was constructed by persons not parties [30]*30to this litigation. From the record before ns it is impossible to determine exactly why it was constructed. Dam #1 is on the property of a farmer who is not a party in this case.
[29]*29
[30]*30Plaintiffs have two types of water permits. Their original permits, with priority dates of October and December 1949, entitle them to appropriate set amounts of water from West Dairy Creek.
Both the 1949 permits and the 1954-55 permits designate the same “diversion point,” which as we understand it, is at point B.②
It is the position of defendants that plaintiffs [31]*31must repair or replace—apparently the latter would be more economical—Dam #1 and maintain it in such a way that no more water passes it than the aggregate they are entitled to appropriate under their 1949 water permits. Defendants wish to have this done so that a larger percentage of the water reaching point B will follow the old West Dairy Creek channel to point D, thus being available for use by riparian owners on the part of the old channel between B and C and D. See, n 3, infra.
What now happens is the surplus of water flowing through the unnamed channel, i.e., the amount over and above that to which plaintiffs are entitled under their 1949 permits, flows past Dam #2, rejoining West Dairy Creek at point D. Therefore, this amount of water bypasses the riparian owners on the old channel (B-C-D) and is not available for their nse.
While the defendants’ goal may be a laudable one, whether they can require plaintiffs to replace Dam #1 presents a question of defendants’ statutory authority. The relevant statutes provide:
“The owners of any ditch or canal shall maintain to the satisfaction of the State Engineer a substantial headgate at the point where the water is diverted. It shall be of such construction that it can be locked and kept closed by the watermaster.” ORS 540.310 (1).
“If any owner of irrigation works refuses or neglects to construct and put in headgates, flumes or measuring devices, - as required under ORS 540.310, after 10 days’ notice, the watermaster may close the ditch, and it shall not be opened or any water diverted from the source of supply, under the penalties prescribed by law for the opening of headgates lawfully closed, until the requirements of the State Engineer as to such headgates, flumes [32]*32or measuring devices have been complied with.” ORS 540.320.
To apply' these statutes to the facts at bar, it is first necessary to define certain terms: (1) natural watercourse; (2) irrigation ditch or canal; and (3) diversion point. There do not appear to be any statutory definitions of these- terms, but they have settled meanings in the cases.
(1) A “natural watercourse” has been defined as a current of water in a channel, and as a living stream with reasonably defined banks. See, Fitzstephens v. Watson et al, 218 Or 185, 344 P2d 221 (1959); Levene et ux v. City of Salem, 191 Or 182, 229 P2d 255 (1951). A natural, watercourse has a definite and at least periodic source of water supply, but there need not necessarily be a flow of water in its channel at all times. See, Wellman et ux v. Kelley and Harrison, 197 Or 553, 252 P2d 816 (1953).
(2) A “ditch or canal,” ORS 540.310, or “irrigation works,” ORS 540.320, are artificial man-made water conduits. They are made by excavation or other means of construction, and are designed to divert a flow of water to areas where it would otherwise not flow because of the configurations of the land. Mancini v. DeLillis, 1 NJ Super 490, 65 A2d 90 (1948); cf., Appleton et al v. Oregon Iron & Steel Co., 229 Or 81, 358 P2d 260, 366 P2d 174 (1961). Unlike some natural watercourses, all ditches and canals are capable of being owned, of., Washburn v. Inter-Mountain Mining Co., 56 Or 578, 109 P 382, 12C Ann Cas 357 (1910), as witnessed by the use of the term “owner” in ORS 540.310 and 540.320.
(3) Water is “diverted” when its flow is turned from the course it would otherwise follow. Thus, [33]*33water can be diverted from one natural watercourse to another natural watercourse, see, Brattain v. Conn., 50 Or 156, 91 P 458 (1907), or from one artificial water conduit to another artificial water conduit. The most common use of the term, however, is when water is diverted from a natural watercourse to an artificial conduit. See, Boyce v. Killip, 184 Or 424, 198 P2d 613 (1948); State ex rel Johnson v. Stewart, 163 Or 585, 96 P2d 220 (1940); In Re North Powder River, 75 Or 83, 144 P 485, 146 P 475 (1915). We believe the term “diverted” in ORS 540.310 and 540.320 is used in this latter sense, as indicated by the phrase, “diverted into the ditch from the stream,” in ORS 540.310 (2). Thus, for purposes of applying those statutes, a person’s “diversion point” is the point at which he causes water that would otherwise flow in a natural watercourse to instead enter an artificial conduit.
When these definitions are incorporated into the statutes in question, ORS 540.310 (1) and 540.320, the rule those statutes express can be paraphrased as follows: A person can be required to construct a head-gate at his diversion point, that is, at the point where he diverts water from a natural watercourse into some artificial conduit. Plaintiffs argue their diversion point is at Dam #2 where they divert water from the unnamed channel (B-Gr-D), which they consider to be a natural watercourse, into their reservoir. Defendants argue plaintiffs’ diversion point is where the unnamed channel, which they consider to be an artificial conduit, forks from West Dairy Creek, i.e., point B.
Eesolution of this dispute as to the location of plaintiffs’ diversion point turns on the ultimate question of whether the unnamed channel is a natural [34]*34watercourse or an artificial conduit. If the unnamed channel is a natural watercourse, then plaintiffs’ diversion point, as we have defined that term, is necessarily at Dam #2, On the other hand, if the unnamed channel is an artificial conduit,, them it would follow that plaintiffs’ diversion point is at point B.
The evidence establishes' that the unnamed channel (B-Gr-D) is a natural watercourse. Some time in the 1920’s or 1930’s, winter flood waters in West Dairy Creek caused a washout of the creek bank at point B, creating the unnamed channel that rejoined West Dairy Creek at point D. Several witnesses suggested the possible reason for the washout was that the old channel (B-C-D) had become clogged with fallen trees and other debris.
Current and prior property owners in the area testified that for many years the unnamed channel has had a well-defined channel and banks. When it was originally formed, water flowed in the uiinamed channel only during periods of high water. As the old channel of West Dairy Creek (B-C-D) became increasingly obstructed, a higher percentage of the water entered the unnamed channel and the flow therein became more permanent. At the time of trial (July 1971), water was flowing through the unnamed channel, but little if any through the old West Dairy Creek channel (B-C-D).
Under the authorities defining a natural watercourse, cited above, we conclude the unnamed channel (B-G--D) is a natural watercourse. Although defendants have consistently referred to the unnamed channel as a man-made diversion ditch, we find nothing in the record that supports their characterization.
It follows that under ORS 540.310 and 540.320 [35]*35plaintiffs cannot be required to replace Dam #1, because it is not located at their diversion point.
As best we understand them, defendants claim additional statutory authority to require the replacement of Dam #1. They rely on:
“Each application for a permit to appropriate water shall set forth * * * the source of water supply * * ORS 537.140 (1)(a).
“An application may be approved * * * upon terms, limitations and conditions necessary for the protection of the public interest * # ORS 537.190 (1).
Defendants rely on ORS 537.140 (1) (a) because plaintiffs’ applications for water permits and water permits themselves all designate point B as their point of diversion. See, n 2, supra. Defendants apparently argue we should regard this designation in the applications and permits as conclusive for purposes of applying ORS 540.310 and 540.320.
We decline to do so. “Diverted” is a term of art in water law, and in the absence of any indication to the contrary we must assume the legislature used it in its technical sense in ORS 540.310 and 540.320. And as stated above, plaintiffs’ point of diversion, as that term is properly defined, is at Dam #2. Nothing to the contrary in plaintiffs’ applications or permits can change that conclusion, which is based on the legal definition of “diverted.” The designation of plaintiffs’ diversion point in their applications and permits must be regarded as something akin to either a unilateral or mutual mistake of law.
Furthermore, the record establishes that plaintiffs never filled in the technical description of their diversion point, see, n 2, supra, on their water permit [36]*36applications. Instead, plaintiffs testified they relied on and deferred to various state and federal engineers to handle these details, being unfamiliar with snch technical matters themselves. This makes it inappropriate to give any conclusive effect to the language of the applications or permits.
Defendants rely on ORS 537.190 (1) because one of the three plaintiffs, a Mr. Spiering, has a water permit subject to the following condition:
“That the diversion works shall include an in-line flow meter, a weir, or other suitable device for measuring the water to which the applicant is entitled.
“That the type and place of the measuring device be approved by the watermaster before the beginning of construction work and that the weir or measuring device be installed under the general supervision of said watermaster.”
Even assuming the reference to a “measuring device” is broad enough to require Mr. Spiering to construct a dam, we nevertheless believe defendants’ reliance on ORS 537.190 (1) is misplaced for two reasons. First, we seriously doubt that the general language of ORS 537.190 (1) authorizes the State Engineer to condition a water permit on the construction of a dam in a natural watercourse, which is what we have concluded the unnamed channel to be. Second, we believe conditions to protect the public interest means conditions designed to, as much as possible, preserve the natural status quo as far as the flow of water so that the rights of lower riparian owners will be protected. But defendants’ demands in this case go much further than that; instead of seeking to preserve the natural status quo, defendants are attempting to make the plaintiffs restore the status quo [37]*37ante so that water flows in the way it did before the cutting action of flood waters created the unnamed channel.③ We do not believe the language of ORS 537.190 (1) or the condition imposed on Mr. Spiering’s permit enables them to do this.
Reversed and remanded for entry of a decree in accordance with this opinion.
More specifically, the permits provide: (1) plaintiff Vanderzanden has a right to use the waters of “West Fork of Dairy Creek and an unnamed lake”; (2) plaintiff Vandehey has a right to use the waters of “West Dairy Creek”; and (3) plaintiff Spiering has a right to use the waters of “West Fork of Dairy Creek.”
