I think both these maps have been entered before. It shows the Flint River and where it adds to the Saginaw Bay. The Michigan map shows where the Flint River is in relation to the rest of the state.
It is safe to say the Flint River is a part of a larger river system.
While the Flint River is part of a larger river system, it also has it's own watershed.
Each river in this water system has it's own watershed system.
A watershed system is about geography and geology. The watershed is about the land that receives water from rain and dew. A watershed also has other resources such as lawn sprinklers and in today's society a watershed also receives water from bottles and water deliver.
That may seem like a silly concept, but, it isn't. Those that think about Earth look to the "natural system" for the water and then assess the "foreign system" for the watershed, including such things as water delivery of water from places outside the watershed. To my knowledge and I will make sure this is fact, Flint River watershed does not have a water bottling plant. As a result water is delivered from outside the watershed for use within it.
This is the Flint River watershed. It has tributaries emptying into the Flint River. It also has "overland" flow that runs off the land into the river. Interestingly, it has a watershed that does not contribute to the Cass River. There is land to the south of the river that belongs to the Shiawassee River that does not contribute to the Flint River watershed.
It seems to me to be a very interesting watershed. It is a significant size for the length of the river. I won't get into specifics, but, during my investigation of the Flint River, it has a unpredictable "recharge." Recharge is the water that flows into the river to replenish the water that runs into a larger river system. When a river has a unpredictable recharge it cannot be a water source. Why? Because a high demand of water use of such a river would mean it could run dry and leave residents without water at all.
My information is from public records, if anyone put an effort forward it could be found.
Setting aside the danger of the water itself, the Army Corp of Engineers would not have approved it for a city's water source for the chance it would not be sufficient for high demand use. The US Army Corp of the Detroit District could be asked to officially evaluate the river flow rate and recharge to determine what I stated as fact. The do all and end all focus on the EPA's responsibility is not the only place that needed to evaluate the work of the Snyder administration.
The Flint River Water Project is ongoing.