SOME PKOBLEMS IN CONSERVATION 43 



The recognized indicators of the level of ground water in the 

 order of their dependability are: (a) the water in an outlet-less 

 pond or lake, the water being an extension of the ground water 

 and rising and falling with the season, (b) Swamp and bog lev- 

 els give the approximate level of ground water but are less sensi- 

 tive to changes in climatic conditions, (c) Hillside seeps or 

 springs mark the line of outcrop for the ground water and are 

 conspicuous along many streams which are in the channeling 

 stage, (d) Artificial trenches and excavations for agricultural, in- 

 dustrial and sanitary purposes give a reliable record of the ground 

 water level. Along this line the ordinary dug or shallow well is 

 most important on account of its almost universal distribution 



In 1909 and 1910 the U. S. Department of Agriculture started 

 an inquiry to determine the stability of the mean ground water 

 level. Questionaries were sent to 33,000 reporters and replies 

 were received from about half the number. The important ques- 

 tions were : "Dates of making wells ; Original depth of water in 

 wells; and Present depth of water in wells." The data received 

 were carefully weighed and tabulated. It is obvious that only 

 the general conclusions can be considered here. The outstand- 

 ing facts obtained are: (a)^ "The depth of the water level beneath 

 the surface varies from place to place, but is in over 60 per cent 

 of the wells, and in most states on the average for all wells, 

 within capillary reach of the surface soil." (b) "A clear quanti- 

 tative indication that the sub-soil water level is, and has been since 

 the settlement of the country, lowering at a considerable rate." 

 Incidentally information was obtained bearing on the general sub- 

 jects of water supply and drainage. 



The ground water must be looked upon as a reserve supply 

 from the standpoint of farm crops and is subject to overdraft 

 during periods of drouth. The data further show "that its upper 

 level is not far from the limit of its availability for crop growth." 

 The universal lowering of the ground water level is a matter of 

 grave concern. The records show that the average lowering for 

 the entire country is about nine feet and for Iowa some twelve 

 and a half feet during the fifty years proceding 1910. The rate 

 of lowering was highest during the early stages but appears to be 

 proceeding at a diminishing rate. If such recedence continues the 

 result is obvious. It will be only a matter of time when the great 

 reserve supply is out of reach of some of our useful plants. It is 

 time to take an inventory of our water resources and endeavor to 



^Bul. No. 92. p. 184. Bureau of Soils. 



