72 BULLETIN 71, U. S. DEPARTMENT OF AGRICULTURE. 



A wide variation in the rates and amounts of run-off is apparent from the 

 above table, according to the distribution of the rainfall, the time of the year, 

 and especially to the condition of the soil before the storm occurred. The soil 

 is spongelike in its action, and the fact that there are few lateral ditches makes 

 a condition favorable for a large absorption. During the heaviest storms the 

 soil became saturated and the water flowed over the surface to the canals. 



In case the run-off from this tract were handled by a pumping plant, the 

 daily run-offs given in the above table would be the amounts available for pump- 

 ing each day, and if cared for, either by pumping or by storing in a reservoir, 

 flooding would not occur. Therefore by assuming a certain pumping-plant 

 capacity the required capacity of reservoir can easily be determined for these 

 storms and for this particular district. In the following tables different pump- 

 ing-plant capacities have been assumed and the corresponding necessary reser- 

 voir capacities have been calculated. These calculations are based upon the 

 storms of March and April, 1912, these having caused the heaviest run-off. This 

 determination is not made with the idea that the results will be capable of gen- 

 eral application, but rather for the purpose of showing a method of finding the 

 proper pumping-plant and reservoir capacities for a given run-off. 



