Geographical Properties

Latitude: 43˚58’ N to 41˚09’ N Longitude: 93˚39’ W to 91˚01’ W The Iowa and Cedar Rivers are major tributaries to the Mississippi River in eastern Iowa. Both the Iowa and Cedar flow in a southeasterly direction discharging to pool 18 of the Mississippi River (see figure). The headwaters of the Cedar River originate in southern Minnesota joining the Iowa River about 30 mi upstream from the confluence of the Iowa with the Mississippi River. Together the Iowa and Cedar River Basins encompass about 32,737 km2, of which more than 90 percent is in Iowa. The Hydrologic Unit Code (HUC) depicting the approved boundaries of, and numerical codes for, river basins units in the United States by the U.S. Geological Survey is 07802 for the Iowa-Cedar Basin. The Iowa-Cedar Basins like much of the Midwest, has a humid continental climate with extremes of both heat and cold. The average annual temperature is 50 °F (10 °C); and locations in the north are lower, under 45 °F (8 °C), Winters are cold and snowfall is common. Spring ushers in the beginning heavy rains and often flooding as the snow melts. Record floods occurred in the Iowa-Cedar Basins in 1993 and 2008. Summers are known for heat and humidity, with daytime temperatures often near 90 °F (32 °C) and sometimes exceeding 100 °F (38 °C).


The region is agricultural with 93 percent of the land in farmland. The total Iowa-Cedar Rivers Basin population is 1,007,575 (2009). The three largest cities are Cedar Falls/Waterloo (population approximately 105,100), Cedar Rapids (population approximately, 126,000) and Iowa City/Coralville (population approximately 70,000). There are numerous small rural towns with populations of 1000 or less across the basins. The total population of Iowa has just reached 3 million people after little or no growth over the last 30 years. The per capita income across the state of Iowa in 2006 was $23, 340.
ICRB Map Click to enlarge.

Land Use

Land use and land cover in the Iowa-Cedar Basin is primarily agricultural with about 93 percent of the total area used for cropland or pasture. Land is largely privately owned. The principal crops are corn, soybeans, hay, and oats. The remaining land area consists of about 4 percent forests, about 2 percent urban and about 1 percent water and wetlands. Industrial outputs are food processing, machinery, electric equipment, chemical products, publishing and primary metals. Iowa produces the nation's largest amount of ethanol and many farms in the Cedar-Iowa basin are growing corn for the growing biofuel industry.

Water resources and uses in the basin

The hydrology of the Iowa-Cedar Basins has changed significantly since settlement and agriculture. The area originally was tallgrass prairie and wetlands, with forests along river corridors. In the early 1900s much of the land was under tillage and the first drainage tiles were installed in many areas to improve farming. Over the last 30 years there has been an increase on drainage tile to eliminate wet areas in fields for more efficient farming and to increase production. The Cedar River has a few existing low head dams that were once used to generate hydroelectric power. In addition, the Coralville Reservoir was completed in 1958 to control flooding on the Iowa River. Municipalities generally withdraw water from wells from alluvial aquifers that are in direct connection from the river. The recreational and wildlife uses contribute to the important economic activities in the small rural communities nearby. The Coralville reservoir on the Iowa River is known as a major area for boating, fishing, and swimming for Iowa City and nearby communities. The Iowa Cedar Basin is the primary contributor of Total Phosphorus (TP) and Total Dissolved Phosphorus (TDP) in the Upper Mississippi River Basin, therefore is an important location to study nitrogen and phosphorus transport phenomena (“hot moments” and “hot spots”) associated with heavy row cropping that contributes to eutrophication and, eventually, hypoxia in the Gulf of Mexico. From this perspective the basin is not only a good test bed for testing management practices (such as conservation improvements to reduce soil erosion from agriculture) but also a remarkable natural laboratory for investigating problems of fundamental scientific interest, (such as identification of nonpoint sources from different agricultural activities).

Policy and Legislation

Most states have enacted clean water legislation. While these statutes usually contain provisions similar to those found in the parallel federal legislation, there may be significant differences. In fact, state statutes may impose requirements that are even more restrictive than the federal law. In all cases, the United States Clean Water Act (CWA) requirements must be followed, and are enforced along with the state enacted statutes and regulations implemented by the state administrative agencies. Iowa has enacted major water quality legislation (Iowa Code - Iowa water quality laws implement portions of the federal CWA and the federal Safe Drinking Water Act. EPA has delegated the National Pollutant Discharge Elimination System permit program to Iowa. The Iowa Department of Natural Resources is charged with implementing the rules and regulations adopted by the Iowa Environmental Protection Commission and with preventing, abating, or controlling water pollution. During the past 30 years, the water community in the U.S. has witnessed a remarkable re-discovery of watershed-based planning and management approaches to resources stewardships. This trend is especially evident in the development of multi-jurisdictional organizations that anticipate and resolve water-related challenges across traditional political boundaries and focus on the laws, policies, programs and projects of various communities toward more efficient, integrated solutions. Cities, counties, states, tribes and federal agencies depend increasingly on interstate and watershed organizations as coordinating bodies for watershed-based planning and development initiatives to manage water supply, flood protection, water quality controls, fisheries management, recreational areas and other independent priorities. In short, this rediscovery is driven by a broader recognition and acceptance of the need for Integrated Water Resources Management.