SOILS OF THE SUTTER BASIN. 5 



to agriculture under altered conditions. Passage of subsoil waters 

 vertically and laterally through the soil and subsoil material will 

 take place much more slowly than would be the case with soil material 

 of lighter texture and less compact structure. Moreover, when pro- 

 tected from overflow the floor of the basin will during flood periods 

 be several feet below the high water level of the adjacent streams. 

 Under such conditions a tendency toward the maintenance of a high- 

 water table may be anticipated. The level of the water table must 

 therefore be maintained at such a depth as to permit utilization of 

 the soil for agricultural purposes by removal of the subsoil waters 

 through effective operation of the pumps. 



This factor in the possibilities in development of the lands of the 

 basin thus becomes the dominant question in connection with the more 

 detailed mapping of the soils of the basin, undertaken in the revision 

 of this portion of the area. 



It will be remembered that in the original report it is recognized 

 that a belt of the main body of the Sacramento clay lying along its 

 outer boundary varied from the typical soil in having a layer of 

 silt of varying thickness overlying the typical clay. In the revised 

 map this belt has been differentiated as a silty phase and its bound- 

 aries placed on the map. Only minor changes in the boundary of 

 the contact of the body originally mapped as Sacramento clay with 

 adjacent soil types, as originally drawn, have been made. In the main 

 essentials, therefore, the revised map confirms the original as to the 

 differentiation and recognition of soil types. 



In considering the utilization of the soils as recognized in the 

 surveys opinion is based upon knowledge of soils in general as well 

 as on a rather hurried study of what is being done on essentially the 

 same soils in adjoining districts that have been reclaimed from over- 

 flow and artificially drained under somewhat similar conditions. 

 The time and opportunities available for this purpose were both 

 limited, and in none of the districts used for comparison were samples 

 collected, nor had the areas been*completely covered by soil surveys. 

 It is believed, therefore, that a conclusion based on a broader study of 

 what is being done on heavy clay soils elsewhere in the United States 

 will be of greater value. To this end a compilation has been made 

 of the salient facts concerning certain heavy clay soils of the United 

 States, especially heavy alluvial soils that have been mapped, sub- 

 jected to mechanical analyses, and studied in the field by the Bureau 

 of Soils. Special attention has been paid to alluvial soils because 

 their origin, topography, and relation to drainage are like those of 

 the Sacramento clay. After this compilation was made only the 

 heaviest, as shown by mechanical analysis, were selected for com- 

 parison. 



[Cir. 79.] 



