POWERS, Justice.
The Texas Water Commission granted the application of Colorado River Municipal Water District seeking a permit to construct a dam on the Colorado River approximately 24 miles southeast of Ballinger, Texas. The permit, embodied in the Commission’s final order, licenses the district to impound 554,340 acre feet of water by means of the proposed dam and also licenses the district to use 113,000 acre feet of water per annum, as follows: 88,000 acre feet of water per annum for municipal and domestic purposes; and 25,000 acre feet of water per annum for forced evaporative cooling and power plant operation in a steam electric generating station to be constructed adjacent to the reservoir. The Commission granted the permit following lengthy hearings before it, conducted under various provisions of the Texas Water Code.1
[560]*560Appellants2 appeared in the proceedings before the Commission and opposed the granting of the permit. They obtained, in a district court of Travis County, judicial review of the Commission’s action in issuing the permit. The district court having affirmed the Commission’s final order, appellants have appealed to this Court. We will affirm the district court’s judgment.
Appellants bring numerous points of error, the majority of which depend upon the premise that the Commission’s final order rests upon an erroneous definition of the term “unappropriated water,” as that term is used in § 11.134(b)(2) of the Code. That section provides that the Commission may grant a permit to use State water only if “unappropriated water is available in the source of supply .. .. ” Appellants assign to the term “unappropriated water” the following meaning: It is that quantity or volume of water found in the Colorado River in excess of the sum total of the quantities designated in all certified filings and permits applicable to the river, to the extent such filings and permits have not been cancelled in statutory proceedings brought by the Texas Department of Water Resources, as authorized in §§ 11.171-11.186 of the Code. Relying on the fact that the uncaneelled permits and certified filings exhibit, in total, a quantity or volume of water in excess of the amount of water found in the river, appellants contend that there was no unappropriated water available in the source of supply and that the Commission therefore erred in issuing the permit.
Appellees reply that the correct meaning to be assigned the term “unappropriated water” is this: It is that quantity or volume of water available in the Colorado River from time to time over and above the amount necessary to meet the requirements of downstream holders of valid and subsisting water rights, within the limits of economic necessity, for the purposes authorized in their certified filings and permits or the purposes authorized by law as part of their riparian right. We agree with appellees’ meaning, which was also that applied by the Commission and the trial court.
The Commission having concluded in its order that “unappropriated water” was available in the river, we must assume that it intended the meaning given that statutory term by the Code. Before discussing that meaning, we point out that the record of agency proceedings reveals that the Commission’s conclusion of law, relative to the availability of “unappropriated water,” rests upon a large amount of technical and other evidence showing the historical usage of water taken from the river and the anticipated usage of such water, taking into account numerous variables. Past usage is, of course, an indication of the quantity required in economic necessity by those persons who have taken water from the river over the years under a claim of right; if large quantities have in fact not been used, though their permits entitled them perhaps to a larger quantity, and quantities of water have flowed unused into the Gulf of Mexico, that is strong evidence that its use was not economically necessary. Moreover, the quantities of water reasonably required by those users in the future, for authorized purposes, may validly be based upon estimates supported by evidence adduced in the agency proceedings; such estimates of future circumstances are often made in similar administrative agency proceedings. Based upon such evidence, tending to show past and anticipated usage of water, the Commission found sufficient unappropriated water available to allow the district’s impoundment of 554,340 acre feet of water and its use of a quantity not in excess of 113,000 acre feet of water annually, for the purposes indicated above. The permit was conditioned upon releases of water, when necessary, to meet the needs of downstream [561]*561holders of water rights superior to those of the district, as will be discussed below.3
The meaning appellants assign to the term “unappropriated water” is, in our view, contrary to the very nature of the appropriative right to water evidenced by the certified filings and permits advanced by them as a basis for the argument that they represent rights to a total quantity of water in excess of that found in the river. It is, in particular, contrary to the principle of “beneficial use” of water found throughout the Code, and the important limitation of economic necessity which that principle places upon the quantity of water to which one may acquire a vested appropriative right by three years actual use of State water. Appellants argue in truth for an anomaly — an appropriative right based not upon the use of water but upon its non-use. In contrast, the meaning assigned by appel-lees to the term “unappropriated water” comports with the statutory principle of “beneficial use” and the nature of the ap-propriative right to water which has always been a right created, defined and governed by statutes which presently find expression in the Code. A discussion of the Code provisions will reveal this to be the case.
Generally speaking, the ownership of most of the water in the State is claimed by the State and is not subject to private ownership. § 11.021. Historically, the legal right to use the State’s water consisted in [562]*562two categories: (1) the right of use belonging to riparian owners, which formerly extended to reasonable quantities of water taken from the watercourse upon which their lands lay; and (2) the right of other persons, irrespective of land ownership, to acquire a right to take and use water found in a watercourse. W. Hutchins, The Texas Law of Water Rights, 101-2 (1961). The rights of riparian owners are derived from the common law and were first recognized in Texas in 1856. Haas v. Choussard, 17 Tex. 588 (1856). The right of other persons to take and use water, which is called an “appropriative right,” has always been a creature of statute, originating in the statutes of Western states where water scarcity made the common law rule imprudent and dictated the more practical public policy decision that the available supply of water be devoted to the highest and best use for the benefit of the maximum number of persons, hence the term “beneficial use.” E. Clark, Waters and Water Rights § 4.1 (1967). Texas first promulgated in 1889 the statutes embodying this doctrine. 1889 Tex.Gen.Laws, ch. 88, at 100. The common law doctrine of riparian rights was never repudiated, however, and our law currently recognizes both doctrines, though the riparian rights doctrine has been severely circumscribed by statute. See e.g., §§ 11.001, 11.-303 -11.324; Hutchins, supra at 101-62. Section 11.303 of the Code now applies to riparian rights the appropriative rights principle of “beneficial use without waste.”
The State’s ownership of State water is a public trust and the State is under a constitutional duty to conserve the water as a precious resource. Tex.Const., art. XVI, § 59(a); Motl v. Boyd, 116 Tex. 82, 286 S.W. 458 (1926); Texas Water Rights Commission v. Wright, 464 S.W.2d 642 (Tex.1971). This duty permeates and governs the State’s administration of the whole fabric of rights and obligations relative to water rights and water usage in our State.
The inherent elements, aspects, or characteristics of the appropriative right to use the State’s water bear most importantly upon the present case, for the term “unappropriated water” finds its correct legal meaning therein. The first characteristic of the appropriative right, whether evidenced by a certified filing or by a permit,4 is that the holder possesses merely a usu-fructuary right, that is, a right to use a particular part of State water. Texas Water Rights Commission v. Wright, supra. The right may be granted only by the State, pursuant to statutory authorization, and the right is limited to using the water for one or more of the specific purposes authorized by statute. See e.g., § 11.023. Moreover, among the authorized purposes, there is a statutory order of preference reflecting the legislature’s evaluation of the relative importance of the various authorized purposes to which State water may be put. See § 11.024.
Unlike the reasonable use limitation which formerly inhered in the riparian owner’s right to use water from an adjoining stream, the holder of an appropriative right is limited to the exact quantity or volume of water stated in his permit or certified filing. But the holder of an appropriative right, within this specific quantitative limit, [563]*563is limited in another way as well, with respect to the quantity or volume of water which he may take and use. That is, the holder of the right is limited to that quantity or volume which can be “beneficially used for the purposes specified” in his permit. § 11.025 (emphasis added). Indeed, the principle of beneficial use prevails throughout that part of the Code which creates, limits and governs the appropria-tive right to use State water.
“ ‘Beneficial use’ means use of the amount of water which is economically necessary for a purpose authorized by [Chapter 11 of the Code], when reasonable intelligence and reasonable diligence are used in applying the water to that purpose.” § 11.002(5) (emphasis added). Hence, any quantity of water the use of which exceeds the quantity which may be beneficially used is “considered not appropriated.” § 11.025 (emphasis added). That is to say, the excess over and above what is economically necessary was never appropriated at all but was taken and, if not returned, used unlawfully. This interpretation is given further force by the statutory provision that one who takes water under a permit is an “appropriator” only to the extent that he may, in fact, use the water for a beneficial use, that is, the quantity dictated by economic necessity. § 11.002(7). Moreover, one taking a quantity in excess of that required in economic necessity does so in violation of a criminal provision of the Code. § 11.081. It should go without saying that one may not acquire a legal right, in violation of a criminal statute, to a greater quantity. Therefore, the holder of an appropriative right is limited not only to the exact quantity or volume stated in the certified filing or permit which evidences his right, but is also limited to the quantity or volume which is economically necessary for the purposes stated in his permit. That this latter quantity must be only an approximation does not destroy the force of the limitation; it simply calls forth, where competing rights conflict or are affected, administrative determinations in the contested case context of APTRA.
The right to appropriate any quantity of water is inchoate and not perfected “unless the water has been beneficially used for a purpose stated in the original declaration of intention to appropriate water or stated in a permit issued by the [Water Resources Commission] or one of its predecessors.” § 11.026. However,
When an appropriator [as defined and limited by § 11.002(7)] from a source of water supply has used water . .. for a period of three years, he acquires title to his appropriation by limitation against any other claimant of water from same source of water supply and against any riparian owner on the same source of supply.
§ 11.029.
In other words, the grant of a license or permit by the [Commission] to appropriate water concludes nobody’s rights, and all who think they are aggrieved by such action have 3 years within which to file suit against the permittee or person taking water thereunder.
******
Permit is synonymous with leave or license, and means no more than that the party has the license of the state to become an appropriator of water upon statutory conditions.
Motl v. Boyd, supra, 286 S.W. at 475 (emphasis added). Thus, a permit is no more than evidence of a right to acquire another right, the right to use whatever quantity of water the holder may require for a beneficial use. Id. at 475. Although a matured appropriative right is a vested right, it is a right limited to beneficial and non-wasteful uses. Texas Water Rights Commission v. Wright, supra.5
[564]*564 Once the right is perfected it may be lost by wilful abandonment for three successive years. § 11.030. In such cases, “the right to use the water is forfeited and the water is again subject to appropriation.” Id. Whether perfected or not, the right may be lost by cancellation of the holder’s permit, “in whole or in part for 10 years nonuse ...,” as a result of statutory proceedings instituted by the Department of Water Resources. § 11.172. However, the Department’s failure to institute such proceedings, aimed at cancellation of a permit, and the right which it allows to make use of State water, “does not validate or improve the status of any permit, certified filing or certificate of adjudication, in whole or in part.” § 11.185. Hence, if an appropriative right has been forfeited as a result of three years wilful abandonment, it is not preserved until such time as the Department chooses, if it ever does, to initiate proceedings seeking to cancel the pertinent permit on the basis of ten years non-use. The statutory provision for forfeiture, set forth in § 11.030, originated in 1913. 1913 Tex.Gen.Laws, ch. 171, § 49, at 370. The provision for forfeiture is available to the holder of a junior appropriative right as against the holder of a senior appropriative right. See e.g., City of Anson v. Arnett, 250 S.W.2d 450 (Tex.Civ.App.—Eastland 1952, writ ref’d n.r.e.); Lower Nueces River Water Supply District v. Cartwright, 274 S.W.2d 199 (Tex.Civ.App.—San Antonio 1954, writ ref’d n.r.e.); City of Corpus Christi v. Nueces County Water Control & Improvement District, 540 S.W.2d 357 (Tex.Civ.App.—Corpus Christi, 1976, writ ref’d n.r.e.). The statutory proceeding to cancel a permit, in an action instituted by the [565]*565State, was first authorized in 1958. 1953 Tex.Gen.Laws, ch. 352, at 867. The constitutionality of the cancellation provision was affirmed in Texas Water Rights Commission v. Wright, supra. In that decision, the court described the appropriative right as a usufructuary right held on a condition subsequent — that the water would be beneficially used. The cancellation proceeding founded upon 10 years’ non-use is, presumably, analogous to an act of re-entry by the State, the owner of the paramount title, based upon a breaking of the condition subsequent.6 There is another kind of cancellation proceeding, originating in 1913 and now set forth in § 11.146(e). The original version of that statute and its revisions by subsequent Legislatures make it abundantly clear that this cancellation provision applies only when cancellation is sought on the narrow ground that a permit holder has failed timely to commence and pursue construction of specified works necessary to divert the water. 1913 Tex.Gen.Laws, ch. 171, § 38, at 367; 1917 Tex.Gen.Laws, ch. 88, § 7, at 212-3.
In addition to being limited to the quantity of water to which an appropriative right may be perfected by beneficial and actual use, the nature of the appropriative right has another important characteristic which finds expression in the Commission’s findings of fact and conclusions of law in the present case. All the relevant statutes since 1889 have declared the principle that, as between appropriators, the first in time is first in right, now subject to certain statutory exceptions and judicial interpretations. The priority of an appropriator’s right is determined presently by the date he [566]*566files his application for a permit. § 11.141. Section 11.027 provides rather simply: “As between appropriators, the first in time is the first in right.” (emphasis added). A user of water under a permit is, of course, an “appropriator” by statutory definition only to the extent he has actually made “beneficial use” of the water taken under his permit, that is, the quantity or volume of water which was economically necessary for an authorized purpose specified in his permit, irrespective of the quantity or volume set forth in the permit and irrespective of any excess he may have taken. § 11.-002(3), (5). His right has been perfected only to that quantity or volume used by him for a three-year period under economic necessity and for the authorized purpose stated in his permit. § 11.026. Any difference between the quantity specified in the permit and the quantity so perfected by actual use is not a part of the appropriative right evidenced by the permit. The holder of the permit has no legal right to its use and was obligated by statute to return it to the source of supply for appropriation by others. § 11.046. The difference “is considered not appropriated” at all. § 11.025.
Assuming two or more competing “appropriators” require a determinable quantity of water, within the bounds of economic necessity, the senior appropriator’s right was formerly exclusive as against all junior appropriators, save for certain exceptions not presently requiring discussion. Nevertheless, in applying such priority the inherent nature of the appropriative rights doctrine has long required an orchestration of the competing rights to avoid waste and to insure the beneficial use of available water. That this orchestration results from the inherent nature of the appropriative right is indicated in the opinion of the Supreme Court of Texas in Ward County Improvement District No. 3 v. Ward County Irrigation District No. 1, 117 Tex. 10, 295 S.W. 917, 918 (1927), where the court quoted favorably from McCoy v. Huntley, 60 Or. 372, 119 P. 481 (1914):
We see no reason why, even in cases involving prior and subsequent appropriations of water, the courts cannot require the appropriators to alternate in the use of the water. The time when water may be used recklessly or carelessly has passed in this state. With increasing settlement water has become too scarce and too precious to justify any but an economical use of it. An appropriator has only the right to use so much as his needs require, and at the time his needs require. And if these are satisfied by a use of the whole flow every other day, or every alternate week, he ought not to be heard to complain. * * * It must be conceded that there is a paucity of authority on the subject of requiring rotation in the use of water between appropriators. The remedy has frequently been applied in cases of dispute between riparian proprietors, and it is difficult to discern any difference in principle between the right of a riparian proprietor and those of an appropriator in the beneficial use of water. The trend of the later decisions is to apply this method where practicable.
The court, in its holding, validated the trial court’s application of the rule to appropriators in Texas, saying the law sanctioned this orchestration of appropriative rights, based in that case upon the jury’s finding that the rotation was the more practical and economical method of distributing the available water in order to meet the requirement of “beneficial use,” irrigation in that case. The Commission has done nothing more than apply the same principle in the present case in an attempt to practically and economically distribute water available in the source of supply and, by orchestration of all water rights, to avoid waste and to assure the maximum conservation of water, as it is charged to do by statutory and constitutional provisions.
The statutory permit procedure is, of course, another important aspect of the ap-propriative right, for the right is dependent upon the permit and it sets the maximum limit of water quantity in which a right may be perfected. § 11.121. A permit may be granted in whole or in part, if the application conforms to statutory requirements, if it is accompanied by the pre[567]*567scribed fee, if unappropriated water is available in the source of supply, and if the proposed appropriation:
(A) contemplates the application of water to any beneficial use;
(B) does not impair existing water rights or vested riparian rights; and
(C) is not detrimental to the public welfare.
§ 11.134(b)(3). We are presently concerned, among other issues, with whether substantial evidence supports the Commission’s finding that “unappropriated water” is available in the source of supply. It is readily apparent that no existing water right may be impaired by the Commission’s grant of the permit to the district. The district must take its place in line subject to the rights given by law to the holders of senior water rights and subject to statutory preferences among water uses. Moreover, the final order of the Commission directs in some detail how such senior rights shall be preserved from impairment, in particulars not necessary here to discuss. It is obvious that the public welfare lies in preventing waste.
In view of the preceding discussion, the term “unappropriated water” must be construed as meaning that quantity of water not required for an authorized purpose by the economic necessity of all downstream holders of vested appropriative rights. Past usage is, of course, an indication of the quantity required in economic necessity by those users; if large quantities have not been used, that is strong evidence that such use was not economically necessary and no one acquires a right to non-use for an indefinite period of time. Texas Water Rights Commission v. Wright, supra. Section 11.-141 gives the holders of existing water rights the legal assurance that their rights will not be impaired by other diversions, but only to the extent of their “beneficial use” of the water, that is, the amount they require in economic necessity, whatever the flow may be in the Colorado River from time to time, and to the extent the law permits an orchestration of all rights to avoid waste. There is more water in the river, from time to time, than all such holders may possibly use in fact — the river does, on occasion, flood. None should be heard to complain if the surplus is stored by erection of a new dam and reservoir, and a portion of it is appropriated to a beneficial use under a new claim, so long as their economic necessities are met, which the present order assures by specific provision and which the law would require in any event. § 11.027; Ward County Improvement District No. 3 v. Ward County Irrigation District No. 1, supra.
The Commission’s conclusion of law, it should be observed, is in the statutory language of § 11.121, from which one must presume that the Commission’s use of the term “unappropriated water” intends the Code’s general concept of appropriative rights to water. So much is implied in the language of the finding. Therefore, instead of the term being vague and indecisive as charged by appellants and the dissent, we take it to have the precise legal meaning assigned to it by the statutes which the Commission is charged to administer “so as to promote the judicious use and maximum conservation ... of water.” § 5.268. These statutes expressly and carefully include throughout the Code the principle of beneficial use, or the quantity of water required to meet economic necessities, and the corollary principle that the beneficial use of water lies in its conservation, while the non-use of it is waste, a result abhorred by the doctrine of appropri-ative rights and a result which the doctrine was specifically designed to prevent. See Texas Water Rights Commission v. Wright, supra; Hutchins, supra at 101-2. The statutes dealing with appropriative rights must therefore be implemented to prevent the waste of water and the principle of beneficial use, or economic necessity, inheres in the very doctrine of appropriative rights. There is no such doctrine without that principle and in promulgating the doctrine in 1889, the Legislature necessarily included that principle. Texas Water Rights Commission v. Wright, supra.
Motl v. Boyd, supra, has been misunderstood by appellants in their contention that the quantities of water specified in all the [568]*568permits and certified filings when totaled, determine within themselves the limit of unappropriated water available in a given source of supply. As said in Motl v. Boyd, supra, 286 S.W. at 475,
The facts as to that question can be determined by [the Board of Water Engineers] by the mere matter of adding up the amount of water previously appropriated [as defined even then in terms of beneficial use] and shown on their records, and subtracting it from the amount of state water which they had previously determined the stream furnished.
(emphasis added). The quoted sentence refers to the power of the Board of Water Engineers to make an ex parte examination, on the filing of an application for a permit, to determine whether unappropriated water was available in the source of supply. § 11.131, formerly Tex.Rev.Civ. Stat. art. 7503 (repealed). The “records,” of which the opinion speaks, are not merely the certified filings and permits which evidence appropriative rights, as appellants contend, but other kinds of records as well, compiled and maintained under administrative procedures which were somewhat different in theory and mechanics from those of the present day. While the permit procedure and other aspects of agency administration are distinctly different now, the principle of “beneficial use,” in terms of “economic necessity,” remains the same. Several statutes in effect at the time of the decision in Motl v. Boyd, supra, will help to ascertain the precise meaning of the case.7
Then, as now, the scope of all appropria-tive rights could not legally exceed the quantity of water which could be applied to [569]*569a beneficial use. Any excess over the quantity “not so applied shall not be considered [by the Board] as appropriated.” Tex.Rev. Civ.Stat. art. 7543 (repealed). And because the Board was directed to determine the quantities “required for irrigation and other lawful uses ..., in order to secure the highest beneficial use of such water,” and to keep “full and proper records of its work, observations and calculations,” we must presume it performed its official duty in all such respects. Therefore, the “records” of the Board included both the quantities specified in the permits and certified filings and the quantities which the Board determined were properly required for lawful use of State water, that is, the quantities which were susceptible of being applied to a beneficial use, measured against the quantities of water actually used.8
[570]*570It is important to note that the gist of Motl v. Boyd, supra, with respect to the point under discussion, is that the pertinent statutes did not afford a right of appeal from the Board’s determination as to whether unappropriated water was available, except under the proposition that the Board’s duty was ministerial.9 If the Board’s records showed that the source of supply contained unappropriated water, the Board was duty-bound to issue the permit; if the records did not so show, the Board was duty-bound to reject the application. Are we to assume that the Board, for an extended number of years, regularly violated its ministerial duty and issued permits authorizing the use of additional quantities of water, notwithstanding that its own records reflected rights in a total quantity of water which exceeded the quantity available in the Colorado River? Are we to assume that the Legislature knew of this violation of duty by the Board and did nothing? Are we to assume that the Legislature intended an appropriative rights system unlike any other in the United States which, contrary to the doctrine’s reason for being, allowed the holders of paper rights to legally compel that water flow unused to the Gulf of Mexico on the chance that they might someday decide to use a quantity of water approaching the quantities specified in their permits and certified filings? Are we to assume that the Legislature intended a useless act in requiring that users of State water report the quantities of water they actually used every year, and for what purpose? Did the Legislature intend to create by its statutes pertaining to such certified filings and permits a class of property wherein a few might obtain a valuable right from the State at a nominal fee, not for their necessities but to enable them to speculate therein for future profit? Are we to assume that the statutory provision requiring actual use for three years, in order that an appropriative right might be perfected in the quantity so used, meant nothing? Are we to assume, conversely, the physical impossibility that all holders of certified filings and permits perfected the full extent of their claim, as measured only by their certified filings and permits, so that more water was actually used than the river contained? These assumptions are required by appellants’ fundamental position; to state them illustrates how impermissible they are. The important point is, however, that the Board’s determination as to the [571]*571existence of unappropriated water was based not upon the amounts of water designated in certified filings or previously-issued permits, but upon records showing the quantities of water the Board had determined from its water-usage reports and its own observations, measurements, and calculations to be the “proper quantities required for irrigation and other lawful uses ... in order to secure the highest beneficial use of such water,” art. 7528 (repealed); “beneficial use” being defined then, as now, in terms of economic necessity and actual use for a three-year period. Arts. 7473, 7475 (repealed).
In summary, the fact that all the certified filings and permits may specify a quantity of water which, when totaled, exceeds the quantity of water in the Colorado River is of no legal consequence in this case, for the only relevant inquiry under the appro-priative rights doctrine and the statutes pertaining to it is the total quantity of water to which appropriative rights have been perfected by three years’ beneficial use, that is, use of the water for a purpose specified in the permits and certified filings in a quantity dictated by economic necessity. This has always been the case since inception of the rights now in dispute. There was no requested finding, indeed, there is no contention, that each and every permit and certified filing pertaining to the Colorado River has been perfected to the full extent of the quantity of water specified therein. Such would be necessary, of course, to support appellants’ contention that these filings and permits set within themselves the total quantity of “appropriated water,” allowing the easy mathematical computation of “unappropriated water,” a negative quantity in this instance under appellants’ theory. See § 11.029.
We hold that the Commission proceeded correctly in the present case to determine the availability of “unappropriated water” on the basis of prospective requirements and historic usage of water along the Colorado River above and below the site of the proposed dam, utilizing, together with other evidence, the opinion testimony of expert witnesses. This manner of proceeding was within the power of the Commission and reflects a correct interpretation by the Commission of the relevant statutes. §§ 5.268, 11.134; APTRA § 13.
It is idle to refer appellees to the Legislature for an amendment of the statutes pertaining either to appropriative rights or to the waste of water occasioned by non-use, as the dissent would do. In the Legislature’s promulgation of the statutory doctrine of appropriative rights, that body did all that was necessary to prevent such waste and allow the procedure followed by the Commission in this instance, for the doctrine is founded upon the principles of avoiding waste and assuring beneficial use, as illustrated by the pervasive and express enunciation of these principles throughout the Code, and as confirmed by the Supreme Court of Texas in Texas Water Rights Commission v. Wright, supra, and Ward County Improvement District No. 3 v. Ward County Irrigation District No. 1, supra.
Other points of error raised by appellants do not depend upon the meaning of the statutory phrase “unappropriated water,” and to these we now turn.
Appellants contend the Commission erred in holding applicable to the proceedings before it the provisions of section 2(p) of the Lower Colorado River Authority Act. That section provides that irrespective of any rights held or acquired by the Authority, for the generation of hydroelectric power, its right to impound “flood waters” of the river and to use them for the generation of hydroelectric power “shall be subject to the rights of any other person, municipal corporation or body politic” which had previously acquired, or may subsequently acquire, the right to impound such waters and put them to beneficial use under a permit issued by State authority. Appellants’ contention that the statute gives priority in such “flood waters” only to holders of permits which were subsisting at the time of the statute’s enactment is patently wrong, for the statute expressly makes the Authority’s rights subordinate as well to rights acquired under permits issued [572]*572“thereafter.” Appellants also contend, however, that the statute is expressly limited to declaring superiority with respect to rights in “flood water” and, for that reason, they suggest that we “should strike from the findings of fact and conclusions of law and from the permit itself all references to the Lower Colorado River Authority Act, Section 2(u).” They do not suggest that the error by the Commission, if error there is, prejudices any substantial right they possess. APTRA § 19(e).
We do not see that our striking the relevant findings of fact and conclusions of law, based upon an allegedly erroneous interpretation given the statute by the Commission, will cure any prejudice, even if such existed. Section 2(p) is a statute presently in force and is a restriction upon the Lower Colorado River Authority which is applicable in any event; it is not a restriction upon the Commission. Section 2(p), orchestrated with §§ 11.027 and 11.141 of the Code and other provisions thereof, will determine the relative priorities of appellants and the district in any conflict which may arise after the district perfects an appropriative right or commences to produce hydroelectric power. We need not, therefore, determine in this proceeding the meaning of the term “flood waters” and the priorities of the parties therein. There being no prejudice claimed by appellants in this respect, the point of error is overruled for this reason.
Appellants contend next that the Commission erred in holding applicable to the proceedings § 11.028 of the Code, which provides in part as follows:
Any appropriation made after May 17, 1931, for any purpose other than domestic or municipal use is subject to the right of any city or town to make further appropriations of the water for domestic or municipal use without paying for the water.
The Commission found as a fact that the foregoing section was applicable to the proceedings and recited that:
. .. appropriations in the Colorado River Basin made after May 17, 1931, for purposes other than domestic and municipal uses should be further appropriated by the domestic and municipal use appropriation granted by this Order whenever priority of appropriation may be enforced.
This finding of fact is rather plainly an attempt by the Commission, albeit an awkward attempt, to state that the permit awarded the district allows the appropriation of water for domestic and municipal uses having priority over previous appropriations made after May 17, 1931; and these earlier appropriations are subject to the district’s permit, by virtue of § 11.028. The awkwardness results from the term “further appropriations” used in § 11.028. The categorization as a finding of fact evidently results from the Commission’s determination of the authorized uses to which the appropriated water must be put; the proposition stated in the finding is rather plainly a mixed statement of law and fact.
Appellants complain that (1) the finding is irrelevant in a proceeding aimed at determining whether to issue a permit; (2) § 11.028 applies, by its own terms, “to the rights of any city or town” and the district, being neither, can obtain no right conferred by the section; and (3) the Commission’s finding does not spell out the mechanics for adjusting the priorities between the instant permit and other rights to water, including the rights of other municipal and domestic users. We overrule the point of error. The finding is relevant because it fixes the uses to which the water can legally be put under the permit, for it forms a condition of the permit as well as a finding of fact. Otherwise, it occasions no prejudice to appellants.
Moreover, we believe appellants err in the meaning they would assign to § 11.028. As originally enacted, § 11.028 provided as follows:
As between appropriators, the first in time is the first in right, provided, however, for all appropriations or allotments of water hereafter made for hydroelectric power, irrigation, manufacturing, mining, navigation, or any other purposes than domestic or municipal purposes, shall be granted subject to the right of any city, [573]*573town or municipality of this State to make further appropriations of said water thereafter without the necessity of condemnation or paying therefor, for domestic and municipal purposes as herein defined ....
1931 Tex.Gen.Laws, ch. 128, at 217. The same act insured the priority of water for domestic and municipal uses by other provisions found in section 1, declaring such use to have the first priority over any other use whatever, and in section 3, declaring the right to take water for such purposes is “primary and fundamental, and the right to recover from other uses, waters essential to such purposes shall be paramount and unquestioned .. .. ” Section 3 also gave the power of eminent domain to all “political sub-divisions of the State, and Constitutional Governmental Agencies exercising delegated Legislative powers,” to take water for municipal and domestic purposes.10 Presently, § 11.024 of the Code sets out the preferences, again giving first preference to water for “domestic and municipal uses, including water for sustaining human life and the life of domestic animals”; § 11.027 declares the first in time, first in right, doctrine; § 11.028 declares an exception to that doctrine in favor of cities and towns, allowing them to make “further appropriation” for domestic or municipal uses; and § 11.033 gives the power of eminent domain in essentially the same terms as the original statute. It is obvious that the present statutes are in pari materia and in cases such as the one before us several provisions of the Code Construction Act, Tex.Rev.Civ.Stat.Ann. art. 5429b-2, apply: it is presumed that the Legislature intended to favor the public interest over any private interest, § 3.01; we may consider, in construing the relevant statutes, the object sought to be obtained, the circumstances under which the statutes were enacted, their legislative history, former statutory provisions, the consequences of a particular construction, and the administrative construction of the statutes, § 3.03; and we must construe special provisions and general provisions so as to give effect to both, if that is possible, § 3.06. (Section references in the foregoing sentence are to the Code Construction Act.) Moreover, we are bound by the fundamental rule that we must ascertain and give effect to the Legislature’s intent; and, in so doing, we must consider and give effect to all laws bearing on the same subject. Jessen Associates, Inc. v. Bullock, 531 S.W.2d 593 (Tex.1975).
The district was created a conservation district, by special law, under Tex.Gonst., art. XVI, § 59, “for the purpose of provid[574]*574ing a source of water supply for municipal, domestic and industrial use and processing and transporting the same ...it is a “governmental agency and a body politic and corporate;” and it is empowered to acquire water appropriation permits and to impound, by means of dams, the “unappropriated flow of the Colorado River . .. . ” 1949 Tex.Gen.Laws, ch. 340, §§ 1, 7, 15, 17 at 655 et seq. In findings of fact not challenged by appellants, the Commission found that the district presently furnishes water directly or indirectly to eight cities and towns and, given its location and distribution facilities, is the “logical supplier of both present and future domestic and municipal water requirements” in fourteen counties named in the Commission’s final order. The permit which forms part of such order authorizes the district to divert and use “88,000 acre feet of water per an-num for municipal and domestic purposes.” The Commission was under a statutory duty to “give preference to applications in the order declared in Section 11.024 of [the Code] and to applications which will effectuate the maximum utilization of water and are calculated to prevent the escape of water without contribution to a beneficial public service.” § 11.123. The preferences listed in § 11.024 are categorized, and assigned priority, based not upon the nature or character of the holder of the water right, but based upon the use of water, domestic and municipal uses being the first preference.
It would exalt form over substance, and destroy the general legislative scheme based upon the priority of municipal and domestic water use, were we to hold that the district, because it is not a city or town, was not entitled to the preference listed in § 11.024. Water supply contracts are subject to public control and the suppliers of water are under a statutory duty to furnish water to adjoining landowners upon reasonable demand. §§ 11.036,11.037,11.038,11.-039, 11.041. Suppliers are also, of course, subject to their pertinent contract obligations, regulated by the State. In the present case, the district is a body corporate and politic coextensive with the geographical areas of several cities to which it supplies water, all of which have statutory authority to acquire a water supply. Tex. Rev.Civ.Stat.Ann. arts. 1015(30), 1109. The manner in which a city exercises this power to provide a suitable water supply rests largely in the discretion of its governing body. Kimbrough v. Walling, 371 S.W.2d 691 (Tex.1963). The meaning for which appellants contend would deprive the governing body of a city of this discretion and require, if the city is to maintain a preferred position for domestic and municipal uses, that the city itself obtain a permit, notwithstanding that the special law which created the district empowered it to do so, for the benefit of the municipalities served by it. We do not see that the Code intended this result. That § 11.028 makes appropriations after May 17,1931, insofar as they are not for domestic or municipal use, “subject to the right of any city or town to make further appropriations of the water for domestic or municipal use” without payment, only reiterates the preference for domestic and municipal use found elsewhere in the Code.
The rule of expressio unius est ex-clusio alterius, relied upon by appellants, is only a rule of construction, subject to the paramount rule that we must give effect to all related statutes. In doing so, we hold that the supervening importance given throughout the Code to beneficial water usage, particularly usage for domestic and municipal purposes, demonstrates the unmistakable legislative intent that such usage is the controlling factor and that the provision relative to cities and towns in § 11.028 was intended merely as an exception to the general rule of first in time, first in right, now found in § 11.027, the applicability of the exception being defined by §§ 11.024 and 11.028 when they are construed together.
We find no error in the Commission’s failure to set forth the mechanics for adjusting the priorities between the district’s permit and the rights of other users of water. That is a matter governed by [575]*575statute and the common law, to be considered when and if a conflict occurs.
Accordingly, we overrule appellants’ point of error which challenges the Commission’s finding that the 88,000 acre feet of water, authorized under the permit, are to be used annually for domestic and municipal purposes.
We have examined appellants’ remaining points of error and find they are without merit. They are, accordingly, overruled. Finding no error, we affirm the judgment of the district court.
Affirmed.