97 



Retum seejMige, liitter Root Rirer, Juh/ 9-14, 1903. 



Discharge of river at ( iraiitf^ilale, Mont -', 320. 9 



Intiow from tributaries 1 - •>-3- ^ 



Total inflow 3, 944. 7 



Discharge of river at Buckhouse bridge 4, 221 . 7 



Diversions through canals l''l • ' 



Total outflow -1' •'''^•"- ^ 



( iaiii in 48 miles "l^.S. / 



Tlie tliird series was made from Auj^ust 7 to U, at a time when the 

 discharge of the river and the various tributaries wa.'^ quite low. The 

 results of the third series of measurement, expressed as l)efore, are as 

 follows: 



Return seepage, Bitter Root River, August 7-14, 1903. 



Discharge of river at Grantsdale, Mnnt 325. 5 



Inflow from tributaries -09. 5 



Total inflow 535. 



Discharge of river at Buckhouse bridge 1 , 536. 8 



Diversions through canals 111.8 



Total outflow 1, <>-l8. 6 



Gain in 48 miles 1, 113.6 



The foreooing- figures show that a large volume is held Ijack during 

 the flood period, when all the natural channels are full, and that nmch 

 of the water which is temporarily stored in this way returns to the 

 channel of the river to augment the flow during thv latter part of the 

 season. According to the measurements, a volume of 1,901 cubic feet 

 per second was retained on June 11-15. The only way to account for 

 this loss is by infiltration in the soils and subsoils of the valley. It is 

 probable this process went on over about 480 square miles of open, 

 gravelly soil, and if this is so it is not surprising that a stream of 

 nearly 4 cubic feet per second on an average should be absorbed by 

 each section of land. Figure 18 shows that this process of absorption 

 or inliltration of water, if one considers the entire area afl'ected, ter- 

 minated about July 6. After this date there is a gain instead of a loss. 

 This gain is small at first, but at the end of thirty-seven days increases 

 to 1,113 cubic feet per second. The conditions found between August 

 7 to 11 are remarkable. The total discharge of the stream at Grants- 

 dale is only 325.5 and that of all the tributaries 209.5, or 535 cubic 

 feet per second in all. At the .same time there is an available flow of 

 1,648.6 cubic feet per second at a point 48 miles farther down the 

 stream. In other words, the increase is more than double the ordinary 

 flow of the stream. 



