Water Quality

Nutrients such as nitrogen and phosphorus are important elements to a healthy river ecosystem, but too much is dangerous. Excess nitrogen and phosphorus from farming and sewage end up in our rivers and waterways, causing harmful algae blooms.  An algae bloom is where algae grow out of control and produces toxic or harmful effects on people, fish, shellfish, marine mammals, and birds. Climate change increases and intensifies rainfall, which causes more nitrogen and phosphorus to run off and enter our rivers.

Cities and towns rely on drainage systems to manage stormwater. Drainage systems are channels and pipes that carry the water away from homes, roadways, and buildings during storms.  During rain events, water that cannot seep into the ground runs off the land and into the drainage system.  Unfortunately, the drainpipes that were built a long time ago aren’t big enough, so extra rainfall has nowhere to go. The extra rainfall, or runoff, backs up on roads and homes, causing flooding. This runoff rainwater becomes polluted with fertilizer, oil, pesticides, dirt, bacteria, and other contaminants then flows into our streams, rivers, lakes, and the ocean degrading the quality of our drinking water and damaging habitats.

In addition to flooding, the increased number and intensity of storm events degrade the water quality of natural waterbodies. As our cities have grown, more rain falls on rooftops and pavement instead of sinking into the soil where it can be filtered and cleaned. This excess rainfall does not seep into the ground, so it becomes runoff. When large amounts of runoff flow directly into drainage systems, these drainage systems can become overwhelmed. 

Some cities, like Chicago, have drainage systems that carry both stormwater and sewage. During intense rain events, raw sewage combines with stormwater and overflows into our waterbodies. This contaminates our water supply and can make waterbodies dangerous for recreational uses such as swimming.  One study estimated that “increased storm events will lead to an increase of up to 120% in combined sewer overflows into Lake Michigan by 2100 …, leading to additional human health issues and beach closures” (Pryor et al. 425). 

The water we drink comes either from an aboveground river or lake or from an underground waterbody called an aquifer, also termed groundwater.  Extra runoff from larger rainfall events can enter your water source and contaminate it, making it unsafe to drink.  Increased frequency and intensity of rainfall can bring unhealthy toxins, bacteria, parasites, and harmful algae into our water supply, which impacts our health and well-being.  Overall, climate change is expected to degrade water quality. 

Both the Illinois Department of Natural Resources and the Illinois Environmental Protection Agency (IEPA) manage water resources in the state. In addition, local authorities generally manage stormwater for their communities. We all need to work together to address the water quality impacts from climate change. 

Stormwater and urban runoff issues are addressed by local authorities when developing their communities. The Office of Water Resources (OWR) at IDNR works with communities to provide flood control planning and urban flood control. OWR provides general technical assistance from the planning to the design and construction phases of a project. OWR can assist a community when problems arise. Here are some of the ways they assist communities: 

• Flood Control Reconnaissance Studies
• Hydrologic and Hydraulic Modeling
• Strategic Planning Studies
• Design and Construction Phase Services
• Dam Modification Studies

The Illinois Environmental Protection Agency, specifically the Bureau of Water, monitors and regulates the quality of the state’s surface and groundwater resources. They monitor and regulate community water supplies and regularly inspect sources of water pollution and drinking water treatment facilities. They ensure compliance with regulatory standards and enforce regulatory requirements.   

IDNR Office of Water Resources
This webpage provides information about IDNR’s Office of Water programs. It provides access to a variety of helpful water resources, including flood maps, flood preparedness, water permitting, and more.

IEPA Bureau of Water
This webpage contains information about how IEPA monitors and regulates water quality in Illinois. It includes information on drinking water, stormwater, groundwater, storm water permits, water quality standards, and much more.