15 



to the reclamation of the delta lands of the Sacramento and San 

 Joaquin Rivers in California there were approximately 180,000 

 acres of tules, cattails, and sedges growing in dense formation 

 and transpiring heavily. Much of this area is now farmed, and 

 the remaining growth is chiefly along stream channels and in 

 other unreclaimed places. 



Tules also are products of undrained agricultural districts 

 which have developed swamp areas through overirrigation. They 

 soon appear in the shallow water of marshy places, and are par- 

 ticularly iindesirable in drainage ditches. However, it has been 

 learned by investigation (U) that large areas of tules do not use 

 as much water per unit of area as those in the relatively narrow 

 ribbons of growth along ditches and other stream channels. 



Ditchbank vegetation is subject to exposure from sun and 

 wind with little protection from surrounding growth and tran- 

 spires freely. It is well known that such vegetation is of the 

 water-loving type, the use of water by a few species having been 

 investigated. Where such studies have been undertaken, individual 

 plants or groups of plants have been gro'/m in tanks and the water 

 requirements measured. Attempts have been made also to determine 

 the quantity of water consumed by mixed growths of willows, tules, 

 cottonwoods , and other wet-land vegetation growing under natural 

 conditions, but these have been limited in scope. 



