Cornell's School Engineering has a highly flexible Engineering program
where do you show that the program is flexible? examples?
To get people to stop releasing the house waste into this network of streams would be a herculean task.
so do you want to fix the system, or the people?
It will take a lot of planning and time to execute this task.
you already mentioned this...don't sound too discouraged, that dampens your essay
If I intend to find solutions to all these problems, I must have knowledge of the environment,town planning and biology.
you're not very confident...
be more down the line of I want to solve this prob because... and Cornell will help me in achieving tehm because (and talk about the prog(s) you like)
I need to have studied more than one field
what fields?
overall, your tone is very...hesitant. you use a lot of "if" which makes you sound not determined.
Instead, say what you want to do, and why, and how Cornell will help you achieve. GO on their website and find specific programs. You've gotta say WHY CORNELL, not why engineering.