The costs were to be paid by the parties in proportion to the benefits, as determined by the engineer employed; and no tracts of land were legally entitled to outlets into the drains until those costs were paid. The whole contract shows clearly that the intended drains were for Section 35 alone. Plaintiff and the trial court relied upon the statute, section 465.22, above quoted, and upon such cases as Johannsen v. Otto, 225 Iowa 976, 282 N.W. 334, McKeon v. Brammer and Stouder v. Dashner, both supra, and Cundiff v. Kopseiker, 245 Iowa 179, 61 N.W.2d 443. In so far as this statute and these cases have any bearing upon the litigation before us, they hold, in the language of the Johannsen case, page 979 of 225 Iowa, page 336 of 282 N.W.:

But this rule has been modified in the interest of agriculture to permit the upper proprietor to drain his land into a natural watercourse without liability to a lower proprietor for resulting damages, although the effect is to throw the surface water in somewhat increased volume at times on the servient estate. Martin v. Schwertley, 155 Iowa 347, 351, 136 N.W. 218, 40 L.R.A., N.S., 160; Board of Supvrs., Pottawattamie County v. Board of Supvrs., Harrison County, 214 Iowa 655, 669, 241 N.W. 14; Johannsen v. Otto, 225 Iowa 976, 978, 282 N.W. 334. [2] It is to be pointed out that under modern definition a definite channel with well-marked sides or banks is not essential to a watercourse.

The trial court pointed out that the maps and plats of the drainage district show that the tile lines constructed by the district are 40 rods north of the south border of the Brammer farm so there was no direct connection with the McKeon tile line to the drainage district tile line, and he held in effect that, even though the tile line brought water from a farm outside the district and finally outlet into a public drain on Brammer's land, the agreement was lawful for the tile line was constructed in the natural course of drainage and the fact that the water from the McKeon farm came through a tile did not appear to add any substantial burden to the district above what natural drainage imposed. He drew support for his finding from Cowley v. Reynolds, 178 Iowa 701, 160 N.W. 241; Johannsen v. Otto, 225 Iowa 976, 282 N.W. 334; and section 465.22, Code, 1946. The cited cases hold that when water is moved from the dominant land to the servient land by nature or by a tile line in the natural course of drainage, the water becomes the water of the servient owner and the function of the drainage district on the servient land is to drain away the water in the district that arrives in the district by nature or in any legal manner. The trial court in his findings stated:

McKeon v. Brammer, 29 N.W.2d 518, 521 (Iowa 1947); accord Johannsen v. Otto, 282 N.W. 334, 336 (Iowa 1938).