More Changes of the Colorado River 



53 



action of the water might send the prin- 

 cipal current to the sea in this way.* 



Shortly after that observation was 

 made the entire stream was diverted into 

 the Salton basin for a time, leaving the 

 bed of the river bare for more than a 

 hundred miles. With the restoration of 

 recent conditions the Colorado resumed 

 its way to the Gulf, but in the mean time 

 such erosion and formation of bars had 

 taken place in the section affected by the 

 tides below the "Colony" mesa that the 

 main current flowed through the Santa 

 Clara Slough, if reports from three dif- 

 ferent sources are to be credited. 



The consequences of this change are 

 somewhat momentous. The main mouth 

 of the river was formerly 20 or 30 miles 

 farther northwest of the new debouchure, 

 and with the converging shores of the 

 Gulf gave conditions which, with the 

 spring tides at from 30 to 40 feet, pro- 

 duced a marked bore, being felt many 

 miles upstream, both in the Colorado and 

 the Hardy. The new channel reaches 

 sealevel by a much more gradual descent 

 and without the strong current and con- 

 verging shores favorable to developing 

 the bore. 



The new mouth will become the center 

 of a new series of mud flats, which fringe 

 the shores already for a distance of 50 

 miles. The deposition of silt will operate 

 to close the eastern channel between 

 Montague Island and the mainland, 

 which has long since ceased to be navig- 

 able and will soon afford material which 

 willbe piled by the tides in the deeper 

 channel to the westward, with the final 

 result of filling it more or less com- 

 pletely, thus forming a brackish or saline 



* Bull. Amer. Geog. Society. January, 1906. 



lake comprising Sargents reach and the 

 Great Horseshoe Curve 50 or 60 miles 

 in length, into which the seepage waters 

 of the Hardy will flow, charged with the 

 salts picked up from the mud volcanoes 

 to the northward. Before the channel is 

 closed, however, the action of the tides 

 will carry salt water far up the channels 

 of both the Hardy and the old estuary, 

 with a pertinent effect on the vegetation 

 on the extensive tide-washed flats. 



The new eastern channel is one prob- 

 ably not previously occupied by the river 

 in its present condition, and the change 

 adds to the delta the triangular area 

 enclosed by the old channel below the 

 "Colony mesa" to the Gulf, and the new 

 channel, inclusive of great expanses of 

 mud flats, and a range of gravel dunes or 

 hillocks which find their culmination at 

 the extreme northern end of the triangle 

 immediately below where the new channel 

 takes off from the old one. 



In addition to increasing the area of 

 the delta, serious disturbance of the plants 

 and animals over an area of several hun- 

 dred square miles may ensue. In a large 

 part of it the composition of the flora will 

 be totally altered. It is needless to say 

 that the meager agricultural operations of 

 the few Cocopah Indians who frequent the 

 region will be seriously disturbed. So far 

 as might be inferred from the recon- 

 naisance already made of the conditions 

 of flowage into the Laguna Maqutata, in 

 the extreme western portion of the delta, 

 no serious effect will be apparent in its 

 irregular filling and shrinking by evap- 

 oration. 



D. T. MacDougal, 

 Director of Botanical Research, 



Carnegie Institution*. 



