second, that retardation of flow simultaneously on all head- 

 water streams of a river system will render flood and low- 

 water control less difficult on the main stems. This point of 

 view is not without engineering support of highest standing, 

 especially in Europe where experience with works of this 

 kind is much greater than in the United States. The late 

 Allen Hazen, a leading engineer, said: 



Lakes and reservoirs sometimes play an important part in modifying 

 and reducing flood flows in the streams that flow from them. The total 

 flow is not reduced but it is spread over a longer period. Some reservoirs 



* * * are normally empty and their capacity is always available for 

 holding back flood flows * * *. Other reservoirs have been built to 

 conserve water for navigation, irrigation, power, or public water supply. 

 Such reservoirs will also hold back flood flows but in varying degrees 



* * *. The meadows along many streams are overflowed at flood 

 stages and this storage capacity tends to reduce the maximum flood 

 flows in the valley below by extending the period of discharge over a 

 longer interval * * *. In other cases there is an important amount 

 of storage in the soil * * *. All storage, whether built primarily for 

 flood control, for development of power, or for any other purpose, will 

 tend to reduce flood conditions * * *. 17 



The question is not one of the influence of a single small 

 creek or mill pond or lake on the flow of the main stem of a 

 great river system, but of the influence on that flow of 

 thousands of marshes, pools, ponds, reservoirs, lakes, creeks, 

 and small headwater streams, combined with agricultural 

 practices that retard run-off and promote infiltration simul- 

 taneously throughout the entire headwater area. 



While immediate responsibility for the disappearance of 

 watershed ponds and lakes, and failure to regulate headwater 

 streams, must be charged to the motives and practices of the 

 owners of the land and to promotional drainage enterprises, 

 a contributory responsibility must be charged to the engi- 

 neering profession generally. If the profession had given as 

 much attention to watershed problems as to large river 

 problems, it could have influenced conduct relating to water- 

 shed waters, in part by direct educational influence on 

 owners of land and on promoters of drainage enterprises, and 

 in part by stimulation of controlling legislation. 



17 Flood Flows, New York, 1930, pp. 149, 150, 151. 



39 



