ON PETITION FOR REHEARING
This opinion supersedes our prior opinion issued January 10, 1984, which is hereby withdrawn.
BURNETT, Judge.This case presents a question of causation. We are asked to decide whether there is substantial evidence to support a jury finding that improper maintenance of a fish screen in an irrigation canal caused a break in the canal wall. This issue is raised by the State of Idaho, Department of Fish and Game, which installed and maintained the screen under a license granted by the Challis Irrigation Company, owner of the canal. The State had a contractual duty, under the terms of the license, to avoid obstructing the flow of water through the fish screen. The canal company and several of its member farmers sued the State, alleging that an obstruction at the fish screen had caused water to back up, breaking the canal bank. Upon verdicts in favor of the canal company and farmers, the State was adjudged liable for the resulting damage.
This case has proven vexatious on appeal. The causation issue, though simple in concept, is complex when viewed against an intricate — and in some respects enigmatic — record. In a prior, unreported opinion, we initially held that the jury’s verdicts were unsupported by substantial evidence of causation. Judgments upon the verdicts were reversed. In response to a petition for rehearing, we have reexamined the entire record and have studied the detailed, supplemental briefs submitted by both sides. The causation issue has been presented exhaustively, and further argument upon rehearing is unnecessary. Upon reconsidering our prior opinion, we now conclude, for reasons set forth below, that the verdicts should be upheld.
In Part I of today’s opinion we broadly outline the rules governing appellate review of the trial record in an appeal from judgments upon jury verdicts. We then set forth the pertinent facts from the record relating to the issue of causation. In Part II we focus upon the legal tests of proximate cause and upon the use of circumstantial evidence to meet those tests in this case.
I
Appellate review of a jury verdict is constrained by several well settled princi*341pies. The general principle, initially articulated by I.C. § 13-219 (now repealed) and perpetuated by case law, is that a jury verdict will not be overturned if it is supported by substantial, although conflicting, evidence. E.g., Quincy v. Joint School Dist. No. 41, 102 Idaho 764, 640 P.2d 304 (1981). From this principle flow a number of closely related corollaries. A question of proximate cause is for the triers of fact to determine, and their determination will not be disturbed on appeal if supported by substantial evidence. Mann v. Gonzales, 100 Idaho 769, 605 P.2d 947 (1980). Where there is conflict as to the meaning of, or reasonable inferences to be drawn from, the evidence, the triers of fact should make the determination. Pierson v. Jones, 102 Idaho 82, 625 P.2d 1085 (1981). On appeal, the evidence in the record, and all reasonable inferences, are viewed in favor of the jury verdict. E.g., Henderson v. Comineo American, Inc., 95 Idaho 690, 518 P.2d 873 (1974).
With these constraints in mind, we turn to the record in the present case, noting the evidence which is undisputed or — if disputed — reasonably could have been viewed in favor of the irrigation company. The company’s canal starts at a headgate on the Salmon River and runs at a slightly declining grade into a farming area. The fish screen is located in the canal roughly two miles below the headgate. The structure includes a trash rack in front of the screen, to catch debris floating down the canal. Approximately fifty feet in front of the trash rack, and along one side of the canal, the State has constructed an opening into a bypass channel which loops around the trash rack and fish screen, rejoining the canal on the downstream side. This bypass opening contains float-activated gates designed to open if clogging in the trash rack impedes the flow in the canal, causing the water to rise.
The canal break in question occurred during the night of June 15 or in the early morning hours of June 16, 1974. During June the Salmon River rose to a record flood level. One of the canal company’s witnesses testified that the river “had been on an increase for approximately five days” before June 16 and had “pretty well stabled out” on the 16th. When the river ran high, the canal headgate became filled with debris; but the river poured over or around the headgate and entered the canal. Although the precise quantity of water flowing in the canal before the break was not measured, it was estimated to be 175 cubic feet per second (cfs) or more — perhaps substantially more. A witness for the canal company later testified that the flow was greater than normal. The canal company could have used “spillboards” below the headgate to divert some of the water back to the river, but it did not do so.
The increased flow in the canal was accompanied by floating debris from the river. The debris began to accumulate against the trash rack in front of the fish screen. On June 14, a work crew from the State was dispatched to the scene. Four men worked all morning, and two men worked that afternoon, to clear the debris. On June 15, a crew of two men arrived. They noticed that debris had accumulated back to the bypass gates and was coming in about as fast as they could remove it. They also noticed that the water level in front of the trash rack was a few inches higher than the level below the fish screen. After clearing debris from about half the width of the channel, they quit and went to work elsewhere for the rest of the day.
That same afternoon a farmer, whose property was located down the canal from the fish screen, measured the water flow against a peg device on his property. He testified at trial that he found the flow to be normal. He also testified that late at night, he rechecked the peg, finding the water level to be somewhat below normal. The following morning, June 16, farmers in the area noticed that their irrigation systems were not working. Upon investigation they found that the canal had broken upstream, nearly a mile above the fish screen. A witness later testified that the break occurred at a “low point” in the canal — that is, at a place where the canal *342had the least distance between a normal water level and the top of its banks.
One observer who viewed the canal above the break point noted that “quite a lot of water” was flowing in the canal between the river and the break point on June 16; but he added, “I have seen more water than that in that canal.” On the downstream side of the break point, farmers discovered a large amount of debris spread upon the bottom of the empty canal, directly in front of the trash rack. The debris occupied the full width of the canal and extended back to the bypass gates. An observer later testified that he saw silt accumulation along the canal banks just upstream from the trash rack twenty-one inches, or about 1.7 feet, higher than the normal water level. Because the normal depth was approximately 3.6 feet, this testimony suggested that the water in the canal had reached a depth of about 5.3 feet near the trash rack before the break occurred upstream. The same observer said he also saw a silt line near the break point “a good fifteen inches” above the normal water level.
At the bypass, one of the float-activated gates was found partially open. The others were found shut. The record does not indicate the exact water levels at which the floats were designed to open these gates; but the gates themselves were only 4.3 feet high. Presumably they were designed to open at a somewhat lower water level. An obvious anomaly, never explained at trial, was how the water could have reached a depth of 5.3 feet near the trash rack without tripping all of the bypass gates. There was no evidence that the gates had malfunctioned. On the other hand, although the gates had been visually checked, they had not been tested on or immediately before June 15. One of the State’s witnesses explained that the gates were not routinely tested because any such test would cause a loss of fish into the bypass channel.
Upon this circumstantial evidence, the canal company and the State asked the jury to draw competing inferences. The canal company asserted that during the night of June 15-16, the trash rack had become so clogged that the water in the canal backed up; and that the increased depth attributable to clogging, when added to the existing flow, caused a canal bank to fail at the “low point” where the washout later was discovered. In contrast, the State contended that debris at the trash rack added little, if at all, to the water depth at the break point. Rather, the State urged that an abnormally high quantity of water entering the canal from the river caused the water level to rise until the canal bank failed.
To aid the jury in evaluating the evidence, the parties presented opinion testimony by two expert witnesses. The canal company’s expert exhibited a diagram showing that if the water near the trash rack had increased to the level of 5.3 feet, and if the water flow at that time had been approximately 175 cfs, the water upstream would have reached a depth approximately equal to the height of the canal bank at the point of the break. The expert did not purport to know, in fact, why or whether the water had reached 5.3 feet near the trash rack; he simply assumed that it had. He acknowledged that if this depth was attained, the primary reason likely would have been the quantity of water entering the canal from the river. But he stated that if the trash rack had been clogged, such clogging could have contributed approximately two to three inches to the depth of the water at the break point upstream. The State’s expert opined that virtually all of the increased depth at the break point would have been due to the high intake of water from the river, and no significant amount would have been caused by the alleged clogging downstream.
Upon this evidence, the jury returned verdicts for the canal company and farmers against the State of Idaho. The jury implicitly inferred that the trash rack had become clogged, obstructing the flow of water in the canal. This is a reasonable inference, supported by substantial evidence. The jury further inferred, implicitly, that the clogging caused the canal bank *343to fail. The latter inference is the point of controversy in this appeal.
The State argues that the trial court should have granted a directed verdict or post-verdict relief, and that in any event the verdicts should be set aside on appeal. The State’s arguments embrace a common question — whether there is substantial evidence to support the inference that the State’s failure to prevent obstruction to water flow at the trash rack caused the damage to the canal. We now focus upon that question.
II
As noted above, the State’s failure to prevent an obstruction represented a breach of a contractual obligation imposed by the license for the fish screen. In order to recover damages for a breach of contract, the aggrieved party must show that his loss actually resulted from the breach. Kg., Graham v. Asbury, 112 Ariz. 184, 540 P.2d 656 (Ariz.1975). In this case the trial court chose to frame the causation issue in terms of “proximate cause.” The concept of proximate cause contains two components — cause in fact, and scope of legal responsibility. W. PROSSER, HANDBOOK OF THE LAW OF TORTS §§ 41-42 (4th ed. 1971). Here, our focus is upon cause in fact.
Proximate cause, in the sense of cause in fact, has been defined as a cause “which in natural and continuous sequence, unbroken by any efficient intervening cause, produces the result complained of and without which the result would not have occurred.” Smith v. Sharp, 82 Idaho 420, 426, 354 P.2d 172,175 (1960). See also Chatterton v. Pocatello Post, 70 Idaho 480, 223 P.2d 389 (1950); Pilmer v. Boise Traction Co., 14 Idaho 327, 94 P. 432 (1908). This component of proximate cause embraces two closely related elements. First, an event is the cause in fact of a succeeding event only if the succeeding event would not have occurred “but for” the prior event. Thus, an act or omission is not the cause in fact of ensuing damage if the damage likely would have occurred anyway. The second element is a requirement that the first event be a “substantial factor” in producing the succeeding event. Munson v. State Department of Highways, 96 Idaho 529, 531 P.2d 1174 (1975). Thus, a defendant’s conduct is the cause in fact of an event only if it was a material element and a substantial factor in bringing it about. W. PROSSER, supra, at 240; RESTATEMENT (SECOND) OF TORTS § 431 (1965).
In the present case, the jury was given an instruction on proximate cause corresponding to Idaho Jury Instructions (IDJI) No. 230. This instruction focuses upon cause in fact, but it does not expressly set forth either the “but for” element or the “substantial factor” element. Rather, the instruction simply explains “proximate cause” as:
a cause which, in natural or probable sequence, produced the damage complained of. It need not be the only cause. It is sufficient if it concurs with some other cause acting at the same time, which in combination with it, causes damage.
This instruction does not completely explain the elements of cause in fact. Moreover, the instruction does not make it entirely clear that in order for a concurring cause to give rise to liability, it must be a proximate cause in its own right. See Miller v. Northern Pacific Railway Co., 24 Idaho 567, 135 P. 845 (1913), and cases cited in 57 AM.JUR.2D Negligence §§ 176-82 (1971). However, this instruction was given without objection by either party. No issue concerning any of the jury instructions has been raised in this appeal. Consequently, we will confine our analysis to causation as the jury was instructed. The question put to the jury was whether the increased water depth in the canal, attributable to clogging at the trash rack, “produced” the damage “in natural and probable sequence ... in combination with” the increased flow of water entering the canal from the river.
A jury is entitled, when making a finding of causation, to draw an inference *344from circumstantial evidence. Henderson v. Comineo American, Inc., 95 Idaho 690, 518 P.2d 873 (1974). In general, a court should not substitute its determination of cause in fact for that of a jury, unless the evidence points only to one reasonable conclusion. Munson v. State Department of Highways, supra. Our Supreme Court has carefully defined the limits of reasonableness within which a jury can draw inferences from circumstantial evidence. In Splinter v. City of Nampa, 74 Idaho 1, 11, 256 P.2d 215, 221 (1953) — a case quoted with approval in Henderson — the Court said:
The underlying principle applicable here is that a verdict cannot rest on conjecture; that where a party seeks to establish a liability by circumstantial evidence, he must establish circumstances of such nature and so related to each other that his theory of liability is the more reasonable conclusion to be drawn therefrom; and that where the proven facts are equally consistent with the absence, as with the existence, of negligence on the part of the defendant, the plaintiff has not carried the burden of proof and cannot recover.
As noted previously, this case was presented to the jury not upon a theory of negligence but upon the State’s violation of a contractual duty to avoid obstructions to the flow of water in the canal. However, the admonition in Splinter, relating to proof of negligence, is applicable to proof of any factual requisite of liability, by use of circumstantial evidence. Thus, in Dent v. Hardware Mutual Casualty Co., 86 Idaho 427, 435, 388 P.2d 89, 93 (1964), our Supreme Court — quoting with approval from Searles v. Manhattan Railway Co., 101 N.Y. 661, 5 N.E. 66 (1886) — stated:
When the fact is that the damages claimed in an action were occasioned by one of two causes, for one of which the defendant is responsible, and for the other of which it is not responsible, the plaintiff must fail if his evidence does not show that the damages were produced by the former cause, and he must fail, also, if it is just as probable that they were caused by the one as by the other, as the plaintiff is bound to make out his case by the preponderance of evidence. The jury must not be left to mere conjecture, and a bare possibility ... is not sufficient.
Dent does not stand on all fours with the instant case because the issue here is one of concurring causes rather than of independent causes. However, the fundamental lesson of Dent — that a plaintiff relying upon circumstantial evidence must show his inference of causation to be more probable than any opposing inference — is applicable here. Thus, the question on appeal is whether the jury, following the instructions given in this case, reasonably could have inferred that the canal failure more probably resulted from clogging at the trash rack, in combination with the increased flow from the river, than from such increased flow alone.
The jury was entitled to believe, and therefore we accept, the opinion of the canal company’s expert that clogging of the trash rack could have contributed as much as three inches to the abnormal depth of water in the canal at the break point. These three inches represented a significant fraction (twenty percent) of the fifteen inches — over the normal water level in the canal — necessary to reach the top of the banks. The jury also was entitled to believe, and we similarly accept, other testimony that the rising river had “stabilized” by June 16 and that water then entering the canal was less than the quantities observed on other occasions. From this evidence we believe a jury permissibly could have inferred that the flow entering the canal from the river during the night of June 15-16 remained at a level within the canal’s capacity; but that when this level was augmented by water backing up from the clogged trash rack, the canal failure followed in natural, probable sequence. We further believe a jury reasonably could have found this scenario more probable than the State’s theory that the canal failed solely because of high water intake from the river.
*345The question admittedly is a close one. As our colleague notes in his dissenting opinion, the canal company’s own expert testified that high water intake was the “primary” cause of the washout. However, such testimony did not shield the State from liability under the jury instruction on proximate cause given by the district court. We also acknowledge that the expert referred to the canal company’s theory as “speculation.” However, when examined in context of the expert’s full testimony, this comment need not have been interpreted by the jury as an expression of disbelief in the company’s claim. The same witness declared that “[t]he trash in the canal undoubtedly aggravated the situation.” Finally, the expert conceded that when he calculated the increased depth due to clogging, he had not been informed of the elevation difference between the tops of the bypass gates and the water level reportedly reached at the trash rack. However, his testimony — again, taken as a whole — plainly indicated that his calculations were postulated upon an impedance of water flow at the trash rack, not upon a complete blockage. The fact that some water would have escaped into the bypass channel was not fatal to the expert’s analysis.
We conclude that the jury’s inference of causation was supported by substantial, though conflicting, evidence. The verdicts will not be set aside. Judgments upon the verdicts are affirmed. Costs to the canal company and farmers. No attorney fees on appeal.
WALTERS, C.J., concurs.