Cities Skylines Dams, Levees and Water Control Guide

Cities Skylines Dams, Levees and Water Control Guide by 5463728190

I got really pissed at building dams and ended up spending many hours figuring out how they work and I found some interesting things about them. Dams are by far the most complicated type of power resource in the game, and this is further compounded by the fact that water is dynamic and simulated. Here I will list my findings and how they work, hope this is helpful.

Notes and concepts pertaining to this topic

This game simulates water. Water moves really, really slowly. To understand a system of water at its most stable configuration, you should wait a few minutes or more (the longer from the source you affect a system the longer you need to wait). This is because your effect on the system will need to travel to the source and back. This “wave” of travel will happen a few times before your system stabilizes. This is often why when you first get a dam running the numbers for power production will jump around.

How do I get the damn dams to work and make them efficient

Dams function by the difference between the height of the water on one side and the other. You will also need to have a current of water for it to run. If you want a constant and stable source of hydroelectric power, you will need to have a flow of water that is faster than the amount of water the the dam releases.

When you first put down a dam it will attempt to store water on its back side. Once the dam hits the line at the top (the line that separates the straight part and the sloped part that slopes into a road), it will start releasing water from the bottom of the front side. This generates power. If the water on the back side does not reach the line, the dam will never release water and will never generate power.

I do not know for sure if the width of the dam matters. However, the speed of the current does for sure. Due to the way the game spawns water for rivers, speed is, for the most part, inversely related to how high you can get your height difference. Also from what I can tell the speed also effects your power generation. You will need to have a balance between speed and height of the dam.

For example. If reservoir does generate a small current towards the dam (smaller than the amount of water the dam will output), what will end up happening is that the dam will slowly fill until the line. The dam’s power generation will start to climb from 0 MWs as it releases water. Since the refill rate of the reservoir cannot match the output rate of the dam, the water level will start to drop. As the water level drops, the power generation of the dam will slow down. It will slow down until it hits 0 MWs and will stop outputting water. It will then wait for the reservoir to fill back up to the line and repeat the cycle. If you haven’t figured it out yet, this is really bad for your city. For sections of time your cities will get power and for other sections of time your cities would not and have blackouts. Always watch the dam for a few minutes to check that it is stable.

Compare this dam with this other dam. Notice how the first dam, although higher, has less power generation than the second dam. The reason for this is that the water level behind the first dam is so high up that the flow is too little. You’ll notice that the dam is in releasing water, just very little of it. The second dam has the exact opposite problem. It is too low and the current is too fast. It cannot keep up with the speed of the water so it cannot maintain a large height difference. The current does drive a larger amount of power than the first dam though.

Here’s another example on a map I edited to test the effect of water flow on dams. This river is using the highest setting for water strength. ignore the 3 dams to the back, they don’t actually touch the water, I was using them to test something else. The original configuration I set the dam rather high, and as a result, the water source did not produce enough water for the water level to reach that height so the dam cannot function and it produces 0 MW a week. In my second configuration, I set the dam to be slightly lower, low enough for the output to match the water generation of the river. As a result the power output hit its maximum at 1600 MW per week.

The water spawns for a river generally will not exceed a certain height. This is generally the maximum height where you should put your dam. If you attempt to put it higher, most of the time there will not be a big enough current of water to fill it up fast enough or even hit the line for the dam to start producing power.

Some details concerning placement

The height of the dam will depend on the lowest of the two points of the dam. The problem is that not all river banks are of the same height on both sides. You can either just place them lower on the hill (like my picture above), or elevate it by placing an elevated road on the lower bank and dragging it across. This will require trail and error. This is also how I place levees in a later section. You can do really dumb things like this by using roads. This is also an easy way to flood your cities.

The estimated number of power when you place the dam does not reflect the true output of power of the dam. I have gotten 400 MWs of power where it says 0 MWs. You can also get lower output than the estimated one. Best way to learn is by trial and error. A good way to measure the power output is the strength of the current and the height of the dam. The height of the dam is more important than the height of the river because you can sometimes place it higher than the river and it will work, assuming the current is strong enough.


The maximum output of a dam is 1600 MW per week, at that level it is the second most efficient power source in the game at $2 per MW per week (the first being the fusion power plant). The next most efficient power source is the solar power plant, at $7.5 per MW per week. For your hydroelectric dam to break even against the solar power plant, your dam will need to make at least 426.667 MW per week. The interesting thing is that even if your dam only generates 200 MW per week, it will only be tied with the oil power plant as the in terms of efficiency.

Here is a chart for power efficiency:

Power SourceCost of 1 MW per week
Fusion Power Plant$0.5
Hydro Power Plant (at 1600 MW)$2
Hydro Power Plant (at 800 MW)$4
Solar Power Plant$7.5
Hydro Power Plant (at 400 MW)$8
Wind Turbine (at 8 MW)$10
Advanced Wind Turbine (at 20 MW)$10
Nuclear Power Plant$12.5
Coal Power Plant$14
Oil Power Plant$16
Hydro Power Plant (at 200 MW)$16
Hydro Power Plant (at 100 MW)$32


Levees (also known as dikes) are structures which are placed alongside rivers to increase the height of the river bank and therefor the capacity of water the river can hold. Due to varying heights in terrain in this game, sometimes it is beneficial to place levees behind the dam so that water will not overflow the banks. Overflowing banks generally means that water is going somewhere else and not towards your dam, thereby lowering the power generation of your dam. Here is a diagram of a levee courtesy of the internet and Google.

Sadly, there are no dedicated way of making levees in this game. You can however make simple and quick levees by building roads and zoning buildings along the river banks. that will usually level and hopefully increase the terrain around the banks by a little bit. The only problem with this approach is that often times it does not increase the height enough and the dammed water will still flood over. There is however, a building in the game which excels as blocking water: the hydroelectric dam. Here is an example of me using one to block water from spilling over one side of the bank. Another angle. Sadly this dam did not work due to its height so I lowered it. Don’t worry about the water outside the levee, they got there before I placed the levee. Using dams as levees are expensive, really expensive. However, you can just shut them down and they will then cost no maintenance. The direction that the dam-levee faces does not matter, it’s sole job is to block water and nothing more. There are only two requirement: the game requires that a dam must be placed over water; you must also make the dam-levee’s level line higher then what your reservoir water level is, otherwise it will leak water out. You can simply dam the river first, wait for some water to flood, then dam-levee it. If the flooded water forms a puddle and does not leave and you want to use that piece of land, you can just pop down some water pumping stations to remove them.

Water Control

You can influence and affect the direct and speed of the water. The water pumping station pumps water out of bodies of water. The water drain pipe and water treatment plant pumps water into bodies of water. If you care not for water population and want the faster pumping method I would suggest you use the water drain over the water treatment plant, it pumps more water per area. In this game it takes no energy to pump water from low ground to high ground (otherwise combined with the dam you will lose power overall) so you can in fact put the pumping stations on the low end of the dam and the drain pipes/treatment plants on the high end and it will dump the water that the dam spit out back into the reservoir at no extra cost, increasing the power generation of the dam.

Here are their effects on water:

Water pumping station:

  • Removes water from location
  • Slows or stops current (since water flow from all directions go towards it)

Water drain/water treatment plant

  • Adds water to location
  • Increases current (since water flows out of it in all directions)

An efficient way to fill a reservoir and force a current would be to first place a dam further up and drain almost all the water up to where you would want the actual dam. When that section of the river is almost done draining, place down your actual dam. You can also put the two dams down then drain if you wish. Then you start putting in drain pipes and water treatment plants. Since these buildings can only be placed next to sources of water and can work underwater, you can slowly fill up the reservoir and then place more. A example of such is detailed below. Note: You can only pump out as much sewage as your citizens make and no more than the amount of drains and treatment plants that you have.

Fake reservoirs

Using the dam-levee you can in fact create fake reservoirs, though it would be challenging and using them to generate power through a hydroelectric dam would be even more so. But it is possible:

  1. Apparently I didn’t take pictures of the early steps but here is what the initial phase looks like, the dam was a bit lower so a little bit of water could pass.
  2. Now you put a dam in front of it and start by spewing shit in it, and here’s the water view, the shit spewers are slow, the dam behind it does most of the heavy lifting.
  3. After water filled do the next layer
  4. and the next…
  5. The view from the water panel
  6. Add the opposing dam, the reason why you can place the dam facing backwards here is because at that point the current from the shit-spewers are stronger than the one created by the big dam. Make sure to place it equal or higher than the front facing dam. You can use the road tool to check height. I also replaced the big dam with a taller version so it would stop leaking water.
  7. Start draining
  8. After 3 layers, accompanying water view
  9. Finished draining
  10. 80 MWs of power from my citizen’s shit!

Since the output of the shit-spewers depends on how much shit your citizens shit out, the dam’s power output will grow with your city’s population.

You could also drain the river, put in the spewers, and let the river fill back up. This will create a much larger current that can increase your dam’s power output

Hope that helps you in making dams!

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