Table 1.

Descriptive statistics of environmental variables in the three study areas*

Variables	Aberdeen		Sioux Falls		Rapid City
	Case (n = 172)	Control (n = 370)	Case (n = 114)	Control (n = 347)	Case (n = 195)	Control (n = 543)
	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)
Land cover (%)
Urban	46.7 (33.6)	55.0 (29.9)	43.9 (30.8)	58.4 (28.2)	60.2 (34.5)	61.5 (34.3)
Open developed space	23.4 (16.5)	27.2 (17.7)	29.6 (18.0)	28.7 (17.3)	15.3 (17.0)	18.0 (17.8)
Grass/hay	18.4 (29.2)	8.8 (20.7)	7.4 (16.5)	5.2 (15.1)	10.5 (18.4)	8.8 (17.8)
Cropland	8.5 (20.4)	6.6 (18.7)	16.7 (28.2)	6.9 (18.7)	4.0 (14.3)	1.4 (7.5)
Forest	1.0 (2.8)	0.7 (2.3)	1.4 (4.5)	0.5 (2.3)	5.0 (14.7)	6.5 (17.4)
Hydrology (meter)
Emergent wetland	376.8 (308.9)	447.4 (322.5)	476.7 (450.5)	711.1 (578.4)	1,039.8 (643.7)	1,350.6 (995.2)
Forest and shrub wetland	1,376.6 (779.4)	1,447.2 (868.4)	1,516.0 (981.2)	1,695.5 (978.5)	3,014.1 (2,763.0)	2,992.0 (2,417.7)
Pond	822.4 (470.2)	851.5 (414.8)	795.4 (513.4)	968.6 (582.0)	731.1 (431.0)	865.8 (441.9)
Lake and river	1,577.8 (1,328.9)	1,695.8 (1,704.1)	2,589.1 (3,299.7)	1,932.0 (2,764.8)	1,770.3 (1,011.3)	2,006.0 (1,085.1)
Soil conditions (meter)†
Ponding frequency > 15%	437.7 (363.4)	509.1 (346.1)	1,091.6 (1,794.2)	1,235.9 (1,224.1)	–	–
Ponding frequency > 50%	570.3 (380.8)	587.4 (334.8)	–	–	–	–
Ponding frequency > 75%	573.4 (381.3)	594.3 (337.5)	1,495.4 (2,082.5)	1,578.5 (1,575.6)	8,130.3 (4,037.2)	12,517.4 (8,660.3)
Irrigation (meter)
Water draw point	2,902.8 (2,906.7)	2,969.6 (4,171.5)	2,800.9 (3,425.4)	2,248.7 (2,699.5)	1,971.1 (1,261.1)	5,934.7 (8,558.9)
DEM (meter)	–	–	–	–
Elevation	–	–	–	–	1,017.6 (78.2)	1,077.0 (160.6)

^*DEM = digital elevation model.

^†Sioux Falls data does not include ponding frequency between 50% and 75%. Rapid City data does not include ponding frequency between 15% and 75%.