stream lengths s Computed from county maps (Michigan Department of 

 Conser-'ation) | a crrrection factor (variable) based on the estimated 

 increase due to meandering^ was applied to each computed lengtho 



Stream widths i Average widths were computed from a series of measure- 

 raents and visual estimates taken at varying distances apartj accurate 

 measurements (steel tape) were made at potential control sitesj and 

 at most points where lampreys, nests^ and suitable spawning habitat 

 were located. At the beginning of the 1950 survey^ the majority of 

 widths were determined by direct measurement » As the season progressed 

 and biologists became more experienced^ most widths were determined by 

 visual estimates checked frequently by tape measurementso 



Stream depths ; Depths were determined at the time widths were recordedo 

 Accurate depth measurements in shallow streams were made with a yardsticks 

 The average depth of a stream at any one point was calculated from 

 measurements at the stream center and at points midway between the 

 center and the edges. Individual depths in deep streams (often turbid) 

 were obtained ^^ri.th a sounding line. 



Water velocities; Velocities were determined at the time widths and 

 depths were recorded. At the beginning of the survey, velocities at 

 individual points were taken by the "chip" method (velocity in feet per 

 second was calculated from the time required for a small glass vial half 

 filled with water to float over a measured distance; an average was 

 obtained from three measurements) « As the survey progressed, 

 velocities were determined by visual estimates, checked frequently by 

 the chip method. The chip method was impracticable in many small streams 

 because of obstructions » 



Water temperatures ; Taken with Taylor pocket thermometers to the nearest 

 degree Fahrenheit. 



Gradients ; Determined by visual estimation, and classified as follows 5 



Slight? Stream bed appearing to be flat or with slight evidence 

 of gradients 



Steep's Appearing to be approximately 1° or more. 



Moderates Between slight and steep » 



Visual estimates were accurate enough for the purposes of this 

 survey^ Gradients were noted frequently. 



