Mineral Creek watershed drains 31,425 acres of primarily agricultural land into the Maquoketa River. About 90 percent of the watershed lies in Jones County and 10 percent in Jackson County.
Soils and Geology
The watershed rests primarily in the Southern Iowa Drift Plain; however, the eastern portion of the watershed has areas that are shallow to limestone bedrock. Based on topography and soils, the watershed is best described by having three distinct regions: The upper (west) hilly region, a large relatively flat middle region, and lower (east) region of rugged terrain.
The UPPER REGION, representing approximately 21 percent of the watershed, is characterized by gently rolling hills and well-defined drainage ways. Fayette, Downs, and Exette silt loams are the predominant upland soils, while Arenzville and Chaseburg silt loams are typically found in the drainage ways. Eighty-three percent of the soils in the upper region are in slope classes C, D, E, or F (5 to 25 % slope), leading to a 94 percent HEL classification of the cropland fields in the region. The unincorporated town of Amber, the Edinburg Historical Site, the County Manor, Farm and Landfill, and Central Park and Lake are all located in the upper region. Most of the land is farmed, corn and soybeans being the major crops, with some hay production.
The MIDDLE REGION makes up approximately 42 percent of the watershed. It is less rolling than the upper and lower regions, with longer, flatter slopes. Predominant soils are Sawmill and Colo-Ely silty clay loams, and Muscatine, Dinsdale, and Tama silt loams. Ninety percent of the soils are mapped in the A and B slope class ranges (0 to 5 % slope), leaving only 11 percent of the cropland classified as HEL. The towns of Center Junction and Onslow are surrounded by fertile land, which is almost all intensively row cropped on a corn-soybean rotation. Several large hog operations are located in this middle region.
The LOWER REGION, about 37 percent of the watershed, is much more rugged and remote. About 10 percent of the soils in this region are mapped 478G – Nordness-Rock Outcrop complex, 18 to 60 % slopes. Another 70 percent are in slope classes C, D, E, or F (5 to 25 % slope), mapped predominantly Fayette and Waubeek silt loams. Livestock on pasture and woodland dominate the area, although a significant portion of the upland ridges and side hills are cropped to corn, soybeans, and hay. Ninety-eight percent of the cropped fields are classified HEL in this region.
Two unique natural areas exist in the lower region. The “Seldom Seen” area, which is indeed one of the most inaccessible areas in Iowa, is locally known to be inhabited by a large population of timber rattlesnakes. Steep forested side slopes with rock outcrops, short bluffs and deep crevices in limestone provide ideal habitat and den sites for these and other snakes. Nearby a Great Blue Heron Rookery was recently discovered, and is the only known rookery not located on the Mississippi River. Ornithologists have cautiously monitored the site since its discovery, and have documented from 13 to 17 nests in prior years. Fewer nests were reported, however, in 1999.
Lack of human impact is what has allowed wildlife to use these areas undisturbed for so many years. Biologists agree that keeping accessibility to a minimum and improving water and forest resources will help preserve these areas.
Total annual precipitation in the Mineral Creek watershed is about 34 inches.