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Water Forms


Red ball iconWater Forms

by Jean Cutler Prior

 

Rain dropsWith the puddling of raindrops, water gathers for its innumerable journeys throughout Iowa. As it moves along, water may become part of a kettlehole, a marsh, a farm pond, a river, a flood, an aquifer, a fen, a cave, a spring, or a waterfall. In all of its aspects, water adds fluid beauty to the landscape. Both above and below ground, water is an ever-present geologic force as well as a vital natural resource, and the focus of environmental protection and natural resource issues.

Thousands of years ago, water in its crystalline form of ice carried the raw building materials of much of Iowa’s present landscape into the state within the grasp of massive glaciers. In turn, the melting of these glaciers laid the course of most rivers seen on today’s maps of Iowa. Even the state’s bedrock foundation, whose picturesque ledges and bluffs outcrop along some of these river valleys, originated as layers of sediment settling out of water on ancient sea floors, along coastlines, and in stream channels millions of years ago.

Iowa’s past geological environments supplied the earth materials that contain our present surface and groundwater resources. These materials shape the forms that water takes on the land surface, and they also determine how fast and how far water moves underground and where it can be tapped for wells. They affect groundwater’s natural quality, as well as its vulnerability to contamination introduced from the land surface.

Photo by Photographic Services, The University of Iowa.

 

Clouds   Water circulates through our environment in a process known as the hydrologic cycle. Precipitation from clouds falls to the ground where it may be taken up by plant roots, flow as surface runoff to streams, or slowly percolate deeper into the earth to become groundwater. Water returns as vapor to the atmosphere primarily by evaporation from lakes and streams, and by plant transpiration.

Photo by Photographic Services, The University of Iowa.

 

Marsh   This shallow marsh, with its lush aquatic vegetation, lies along the Iowa River floodplain at Otter Creek Marsh State Wildlife Refuge in Tama County. The sluggish backwaters persist in broadly curved lowland sloughs that were scoured by earlier meander channels of the river. They tend to fill slowly with silt and clay, and are periodically disturbed by returning floodwaters.

Photo by Roger A. Hill.

 

Kettle   Kettle
Photo by Dick Baker.   Photo by Roger A. Hill.

The water in these poorly drained kettleholes accumulates from rainfall and snowmelt as well as groundwater seepage. The wetland features are a legacy of melting glacial ice 13,000 to 11,000 years ago. (Left) Freda Haffner Kettlehole State Preserve, Dickinson County. (Right) Bjorkboda Marsh, Hamilton County.

 

 

Water power   This historic milldam was constructed on the Winnebago River at Fertile, in Worth County, to put the river’s flow to work. The dam raised the river level so the force of falling water could be used to turn wheels and stones within the mill to grind grain into flour.

Photo by Lowell Washburn.

 

Farm pond   A berm built across a drainageway captures the runoff from rainfall, storing it for livestock use. Farm ponds are particularly abundant in the southern half of Iowa where the rolling topography favors their construction, and the lack of abundant groundwater resources makes these impoundments a valuable water supply. Story County.

Photo by Roger A. Hill.

 

Well   The consistent flow of groundwater from this column of concrete and steel at Osage Spring Municipal Park (Mitchell County), resembles a flowing artesian well. The site has yielded a year-round water supply for wildlife, livestock, and people for at least 100 years. Upwelling of groundwater can occur where a water source, confined under pressure by overlying impermeable rock, finds a natural opening to the land surface or is tapped by a drilled well. This groundwater source contains noticeable amounts of dissolved iron (note rust-colored buildup on the column) and hydrogen-sulfide gas.

Photo by Lynette Seigley.

 

Spring   Springs occur where groundwater flows from rock or soil material to the land surface. This spring tumbles from crevice openings in limestone near the entrance to Spook Cave in Clayton County. In northeastern Iowa, springs often flow near the base of steep-sided valleys, where water moving downward through permeable limestone or dolomite encounters less-permeable shale and moves laterally, finding an opening to the land surface along a valley wall.

Photo by Carol Thompson.

 

Cave   Caverns form as groundwater moves through subterranean crevices in limestone over long periods of geologic time. In this scenic chamber, water seeps in along the ceiling and slowly adds more calcium carbonate (lime) to the glistening formations that decorate the cavern walls. Groundwater continues to flow by gravity along the cavern floor and down through other openings in the limestone formation. Cold Water Cave, Winneshiek County.

Photo by Michael Bounk.

 

River   A river is a volume of water flowing along a well-defined channel toward some larger (and lower) body of water. Also, in a river channel the local groundwater table is visible as surface water. Springs and seeps are significant contributors to northeast Iowa rivers. Along the Upper Iowa River in Winneshiek County, limestone bluffs overlook the channel and provide scenic views around each bend.

Photo by Greg Ludvigson.

 

Water   During low-flow conditions along a river channel, it is possible to see the sediments carried by water. These rounded cobbles and boulders are part of the load that is moved during high flood flows along the Skunk River in Story County. Smaller grains of sand, silt and clay can travel farther and gradually settle as the flow volume decreases. The capacity of flowing water to erode and deposit earth materials makes it the most effective geological process shaping the Iowa landscape today.

Photo by Roger A. Hill.

 

Dam   The reservoir of water in Lake Macbride (right) is separated from the Iowa River (left) by a dam near the center of this aerial view. Shown during flood, the muddy Iowa River is moving a greater load of suspended silt and clay compared to the clearer water in Lake Macbride. This reflects the greater land area draining to the Iowa River (its watershed) and the effects of runoff from cultivated land.

Photo by Photographic Services, The University of Iowa.

 

Flood   A flood occurs when a river overflows its banks and spreads out to cover land not normally under water. When these Cedar River floodwaters over Seminole Valley Park in Cedar Rapids recede, cleanup crews will find deposits of sand and silt as well as scoured out areas.

Photo by Peter M. Schulmeyer, USGS.

 

Fen   A fen is a spongy mound of peat fed by mineralized groundwater and supporting a unique wetland flora. In Iowa, these "mound springs" are typically found on hillsides. Note the rust color as groundwater flow comes in contact with the air, causing dissolved iron to oxidize. Silver Lake Fen State Preserve, Dickinson County.

Photo by Carol Thompson.

 

Waterfall   A waterfall is an abrupt step down along a stream’s channel, usually caused as the water drops vertically over an outcropping ledge of resistant bedrock onto softer, more easily eroded rock. A series of five waterfalls breaks the flow of this Story County brook before it reaches the Skunk River.

Photo by Roger A. Hill.

 

Adapted from Iowa Geology 1997, Iowa Department of Natural Resources