I made an account just to say this: As much as I enjoyed the game, the fact that when it gets harder you're dependent on luck is very unfortunate. I used my resources wisely and carefully, however I didn't get pipes or water carts for a very long time, no matter how much I upgraded the system I couldn't get water carts, lost reputation which meant I couldn't buy money. I don't think that this system of randomized carts that come with luck is fitting for a management and strategy game.
There is a hard cap for water carriers, water carts, pipes, and sumps. The game isn't that dependent on luck as there is a set number of cards in a deck that is cycled every few turns and added depending on your advancements in the game. This means that you will always get all available types of cards every time you cycle the deck, you can see which cards you have the possibility of getting by hovering your mouse over the stack of cards on your left. You probably reached the cap for water carts and didn't upgrade your stables for a while or just reached the max amount of water carts, which is 3.