THE IRRIGATION AGb. 15 



Moreover, this decline will be regular and slow, so that it may be in- 

 telligently studied and regulated. We do not know the amount of 

 leakage nor of the annual supply and much less the amount of the 

 stored reserve, yet from the nature of the case, from the principles of 

 hydro dynamics involved, and the nature and extent of the formations 

 bearing water, we may rest assured that the decline will be very 

 gradual. The first signs of diminution will be the stoppage of the 

 weakest wells, those on highest levels or near the margin of the area. 

 If a well has a pressure of 170 pounds and has gradually diminished 

 five pounds within a year without having any wells sunk in its vicinity 

 we may safely calculate that under the same conditions it will last for 

 at least 35 years with a gradually diminishing flow. The multiplication 

 of wells in a vicinity is the severest test of the amount available at 

 that point and the rate at which it is being exhausted. Where such 

 multiplication has taken place it is still a question in most localities 

 whether perceptible diminution of pressure has resulted or not. 



In closing we would emphasize especially the importance of the 

 establishment of a system of careful and prolonged observations upon 

 representative wells throughout the region. Prom data so collected 

 we may hope to arrive at a reasonable and most efficient method of 

 regulating both the number and management of wells, that this most 

 valuable resource may be utilized to the greatest advantage and for 

 the longest period possible. 



