The best way to block Asian carp from entering the Great Lakes from the Illinois River would be to close the locks and dams near Chicago; however, these waterways remain closed because

The best way to block Asian carp from entering the Great Lakes from the Illinois River would indeed include closing the locks and dams near Chicago. However, these waterways remain open due to several reasons:

1. Economic Considerations - The waterways near Chicago are vital for shipping and cargo transportation. Closing the locks and dams could disrupt commercial traffic and have economic repercussions. Businesses depend on these waterways for the transport of goods and raw materials.

2. Transportation - Apart from commercial shipping, these waterways also facilitate transportation for recreational and other vessels. Closing them would limit access and mobility for people who use these routes for various purposes.

3. Water Management - The water system also plays a role in managing water levels and preventing flooding. Closing locks and dams might have implications for water flow and management in the surrounding area.

4. Alternative Solutions - There may be ongoing efforts to find different ways to prevent Asian carp from spreading into the Great Lakes that do not require the complete closure of the waterways. These could include targeted fishing, biological controls, or engineering solutions like electric barriers.

5. Political and Legal Challenges - There are often political and legal complexities involved when making decisions that affect multiple states and jurisdictions. An agreement would have to be reached between various stakeholders before such drastic measures could be implemented.

It is a complex issue where the potential ecological threat of Asian carp must be balanced with the practicalities of managing a major waterway system.