PROBLEMS FROM DEVELOPMENT 49 



permeable glacial outwash at shallow depths, or perhaps the 

 highly mineralized water in the deeply buried Dakota sand- 

 stone (see page 101). 



Grand Prairie, Ark. s Rice has long been one of the prin- 

 cipal cash crops in the state of Arkansas, and most of the 

 state's crop is produced on upland terraces of the Mississippi 

 River alluvial plain in an area extending along the east side 

 of the state from its northern to southern boundary. 



Typical of the rice-producing area is the Grand Prairie, 

 between the White and Arkansas Rivers, some 20 to 60 miles 

 east of Little Rock. Rice growing was begun there on a com- 

 mercial scale in 1904, and in irrigated area increased to 100,- 

 000 acres by 1915, and 160,000 by 1942; by 1949, despite the 

 ever-increasing acreage of rice in other parts of the state, 

 nearly half the total of 400,000 acres was in the Grand 

 Prairie. 



A large quantity of water is used for the irrigation of rice. 

 The fields are flooded when the plants are 6 or 8 inches high, 

 and standing water is maintained almost continuously for 

 2 or 3 months, until the crop is nearly mature. In 1949 about 

 250,000 acre-feet of water was pumped from wells for irri- 

 gation of rice on the Grand Prairie. The soils of the prairie 

 are underlain practically everywhere by a "hardpan," con- 

 sisting of compact clay so impervious as to inhibit down- 

 ward percolation of water — practically made to order for 

 the ponding required in rice growing. The clay in some 

 places is more than 50 feet thick. 



A ground-water reservoir in permeable sand and gravel, 10 



s Reference: Engler, Kyle, D. G. Thompson, and R. G. Kazmann, Ground 

 Water Supplies for Rice Irrigation in the Grand Prairie Re- 

 gion, Arkansas, Univ. of Ark. Agr. Exp. Sta. Bull. 457, 1945, 

 55 pp. 

 io Actually, only a part of a larger ground-water reservoir that extends from 

 north to south across Arkansas, and into adjacent states. Thus, the Grand 

 Prairie might be considered instead as an area of concentrated draft from a 

 portion of a ground-water reservoir. The classification used here is recognized 

 as tentative, pending fuller information. 



