LAND AND OTHER AGENTS OF PRODUCTION 155 



drainage channels, even if cleared, are entirely inadequate to remove 

 the drainage from the district or give a satisfactory outlet for lateral 

 or farm drainage. 



Of the total precipitation that falls upon a given tract of land a 

 certain portion is taken up by vegetation, some is removed by evapo- 

 ration, some sinks into the ground, and some finds its way over the 

 surface into natural or artificial channels and thence into the larger 

 streams. The water removed in the last-mentioned manner is known 

 as run-off; a certain portion of the water that sinks into the ground 

 later appears also as run-off. It is that part of the precipitation which 

 appears as run-off that must be dealt with in reclaiming lands that 

 under natural conditions are perpetual swamps or that are periodically 

 damaged by the overflow of adjoining streams. 



The most important factors affecting the rate of run-off from a 

 given watershed are: precipitation; the size, shape, and topography 

 of the watershed; the nature of the soil; the character of the vegeta- 

 tion; and the rate of evaporation. Of these, the most important con- 

 sideration is precipitation. 



The annual rainfall at Lumberton (a station in the immediate 

 vicinity of Back and Jacob swamps) varies from a minimum of 38 . 43 

 inches in 1909 to a maximum of 62 . 76 in 1901. The table of monthly 

 and annual rainfall shows that February, June, July, and August have 

 a normal precipitation exceeding 5 inches per month. The minimum 

 monthly rainfall recorded was o . 28 inch in October, 1896, and the 

 maximum monthly was 12.52 inches in May, 1901. The maximum 

 recorded precipitation in 24 hours occurred September 14 and 15, 

 1904, when 5.87 inches fell. During 14 years there were 4 days 

 in which there was a precipitation of 4 inches or more and 9 days in 

 which more than 3 inches fell in 24 hours. 



Aside from the storms of 1901 and 1908, there are no storm periods 

 that show an average daily precipitation in this region of more than 

 o. 75 of an inch over a long period of time, and as the heaviest storms 

 generally occur in the months from May to September, when condi- 

 tions are most favorable for the soil to absorb precipitation, and as the 

 soil absorbs water readily and responds quickly to drainage, it was 

 decided that ditches designed to remove a run-off of one-half inch of 

 water in 24 hours from the entire watershed of Back Swamp and three- 

 fourths of an inch of water in 24 hours from the watershed of Jacob 

 Swamp would afford good drainage. The higher rate of run-off 

 assumed for Jacob Swamp is due to the fact that its area is less than 



