Citiziens die too easily

I took on the enlightened task of building an oasis city in the middle of the desert. Something straight out of an arab shriek and a 20th century railroad mogul dream combined. In fact, I was such a visionary that I decided said city should be pedestrian only.

Now, I also added canals to the city to make transportation easier in exchange. But people keep playing dead because in order to cheapen costs, I used sewage watet to fill said canals.

Can't they just wear facemasks or something?