I 



HYDROLOGY OF NEW YORK 



1(53 



within a short distance of the Hudson river, this being the area 

 classified by the State Weather Bureau under the names of the 

 Eastern and Western plateaus. The streams from the northern 

 crystalline area undoubtedly furnish the best water supply of the 

 State. This is probably not due wholly to the character of the 

 rocks, as many other factors contribute to this result. 



The sandstones of the Upper Devonian along the northern 

 boundary of Pennsylvania are bounded on the north by the long 

 narrow belts of outcrop of the underlying rocks stretching in a 

 general easterly and westerly direction. The streams pursuing a 

 general northerly course pass in succession across these. As a 

 rule, the soils of the region are heavy, with considerable clay, and 

 the rainfall being absorbed somewhat slowly, a considerable por- 

 tion of it flows directly into the watercourses. The primeval 

 forest has for the most part been cut away and heavy floods are 

 common, such as those of the Genesee and Chemung rivers, 

 described more fully on a later page. 



The only streams of this region on which extensive discharge 

 measurements have been made are the Genesee river and its tribu- 

 tary, Oatka creek. Streams of similar character in western Penn- 

 sylvania, however, have been measured for a number of years by 

 the Philadelphia Water Department, and the results of these meas- 

 urements are available for comparison and discussion. The 

 results obtained on the Pennsylvania streams, the Neshaminy, 

 Tohickon and Perkionien, are applicable particularly in estimates 

 of the flow of the tributaries of Delaware river, rising in New 

 York State, and to the more easterly streams which form the 

 Susquehanna. 



The catchment basins of the Oswego, Mohawk and Hudson 

 rivers are so highly composite as regards geologic formations and 

 embrace such a wide variation in topography and surface geology 

 that no definite deductions concerning the effect of the formations 

 on water flow have been drawn. The streams of Long Island, 

 rising among the sands, tills and gravels of comparatively recent, 

 unconsolidated formations, offer peculiar conditions, which are 

 discussed on a later page. 



