•rriK LIFE OF DKVrLS LAKE 13 



CLIMATE 



The cause of the decline of the Devils-Stump Lake complex is 

 excess of evaporation over intake. The sources of such intake are 

 two, with a possible third, rainfall, run-off and possibly under- 

 ground seepage. 



The weather bureau record of rainfall at the city of Devils Lake 

 for the twenty-four year period from 1897 to 1920 inclusive shows 

 that the mean annual rainfall is 44.6 cm., the greatest fall occurring 

 in spring and early summer, during the growing season, while late 

 summer and autumn, the harvest time, are apt to be dry. 



Records taken at the Biological Station on the north shore of 

 Devils Lake about five miles distant from the town, from June 29 

 to August 27, 1914, show a precipitation of 10.1 cm. w^ith occasional 

 additional traces, making a total of about 10.2 cm. compared with a 

 total of 10.5 cm. for the weather bureau station in Devils Lake. 

 During summer the rainfall is apt to be local and inconstant, so 

 that while one area maj^ receive a good supply, another, a short 

 distance removed, may receive but little. 



The snowfall is usually light, overaging 82.8 cm. for twenty 

 years. Under the high wind the lake surface is usually swept bare, 

 and the snow piled in heavy drifts about its shores. 



The amount of run-off reaching the lake cannot be estimated. 

 ^\''ith the loss of the supply from the ]\[auvaise Coulee about 1885*, 

 probably due to the extensive settlement and consequent cultivation 

 of the territory contiguous thereto in the early eighties, coupled 

 with the drouth in the latter half of this decade, the drainage basin 

 was reduced to the area immediately bordering the lake, in which 

 there are no streams and only a few feeble springs. Most of this 

 land moreover is either cultivated or wooded, so that there is very 

 little run-off. 



The extensive cultivation of the soil is a well known cause of 

 lowering the w^ater table in the ground thru increased evaporation 

 from the surface and especially thru the transpiration of plants, 

 but it has an even more important effect in preventing run-off. 



The major part of the run-off occurs during the spring thaw, 

 when the ground is frozen to a depth of several feet. The amount 

 of this run-off depends not alone on amount of snowfall, but even 

 more on the character of the thaw. When the latter is sudden, 

 practically all of the melting snow reaches the lake, causing a mark- 

 ed rise ; when gradual, most of the water percolates into the ground 

 and the lake level is but little changed. The average amount of 

 this rise for ten vears has been about 0.15 m. 



*As a result of e.xccptionally hoavy snowfaU in the winter of 1915-16 this 

 coule'e was flowing' approximately 1.3249 cu. m. per day on Aug. 1.5, 1916. 



