HYDROLOGY OP NEW YORK 



337 



Geologically, the catchment area of the Genesee river above 

 Mount Morris lies in the shales, sandstones, etc. of the Portage 

 and Chemung groups. Its extreme headwaters south of the 

 Pennsylvania line issue from the Carboniferous. Generally the 

 soils throughout the whole basin are heavy and tenacious, in- 

 clining to clay. Their capacity for absorbing and retaining 

 water must therefore be considered small. 



Discharge measurements of Oatka creek. The measurements 

 of Oatka creek, referred to in the preceding, were made at the 

 milldam in the south part of the village of Warsaw, in Wyoming 

 county. The dam was new, practically tight, and well adapted 

 for securing accurate results. Measurements were also made 

 of the outflow of the head raceway leading from the dam for 

 different elevations of water on the dam, and a curve prepared 

 from which the discharge of the raceway was read off and added 

 to the discharge over the dam. 



The catchment area of Oatka creek above Warsaw includes 

 27.5 square miles of rolling, semi-mountainous country. The 

 valley of the creek is deep cut, with numerous springs at the 

 headwaters. The catchment is mostly deforested and in a high 

 state of cultivation, the soil inclining to clay for a considerable 

 portion. Geologically the stream lies in the rocks of the Port- 

 age formation, as developed in western New York. The runoff 

 from this area may be taken as typical of many small streams 

 in western New York. 



Discharge measurements of Hemlock lake. Measurements of 

 the runoff of the Hemlock lake area for the water years 1880 to 

 1884, inclusive, were made by the Rochester Waterworks. Hem- 

 lock lake lies at an elevation of 896 feet above tide, and has a 

 length of 6.5 miles, with an average width of about 0.5 of a mile. 

 Xhe area of the surface at low water is 1828 acres. The total 

 catchment, including the area of the lake, is 27,554 acres, or 

 about 43 square miles. The shores are bold, and on the east side 

 rise to a Light of several hundred feet aibove the lake in a dis- 

 tance of 2 or 3 miles. At the head of the lake there is a swamp 

 of 118 acres, partially covered at high water. 



The outflow of the lake during the period covered by the 

 measurements included in the following table may be considered 

 as having taken place at three points: (1) At the natural outlet 



