What are the limits of the Flood option of the Control Water spell?

Question

The control water spell's Flood option lets you:

cause the water level of all standing water in the area to rise by as much as 20 feet. 

Does this create new water, or simply levitate the water already present? Can it be used to target an artificial container?

If yes, what happens if you raise the water level above the apex of its container (say a river above its river bed or a barrel of water beyond its capacity), what happens to the excess water? The spell states:

If the area includes a shore, the flooding water spills over onto dry land.

Does the edge of an artificial container count as a "shore"? If not, what happens to a filled container when the water level rises 20 feet? If it does count as a shore, does the water fill the external space 20 feet above the apex, or is the expected volume of water conserved (as if the apex had been 20 feet higher)?

Essentially, what happens if the container for the water is insufficient to contain the new volume (or levitated volume)?

Answer 1

A barrel of water is an invalid target for Control Water

Control Water states that you must target freestanding water:

Until the spell ends, you control any freestanding water inside an area you choose that is a cube up to 100 feet on a side.

Freestanding water is natural water in lakes, rivers, swamps. Read this answer for more information. While a manmade pond or dam might create questionable situations for your DM to resolve, a barrel of water is clearly not a valid target.

As such when Control Water states:

If the area includes a shore, the flooding water spills over onto dry land.

It is referring to the land surrounding the lake, river, swamp, etc. That is why the wording seems so confusing when you target a barrel, you are using it in a way that is not allowed.

If you target a valid body of water the spell is explicit about what happens, the water level rises and the flooding water spills over onto dry land.

As for your other query:

Does this create new water, or simply levitate the water already present?

You can use the Polymorph spell to transmute a human into an elephant. Even though an elephant has more mass than a human, the spell magically performs the task. There is no real explanation as to how this works, it's magic.

It's the same with Control Water. Nothing is ever created. The water is transmuted from the existing water. The water does not levitate, only the water level rises.

Answer 2

The rules don't say

The only rules we have are the rules you've cited, and those rules are unclear.

When the rules don't cover a situation, the DM issues a ruling. There's actually a sort-of citation for this -- DMG page 5:

The rules don't account for every possible situation that might arise during a typical D&D session. For example, a player might want his or her character to hurl a brazier full of hot coals in a monster's face. How you determine the outcome of this action is up to you.

It would be an error for us to give a specific interpretation of the rules and say "this is the definite correct interpretation." That's the DM's job. We especially want to avoid a situation where a player points to our answer and tells the DM: "You have to rule this way because this citation on the internet says this is the correct answer!"

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If this DM had to issue a ruling on control water, I would probably rule that the spell can create a 20-foot-high water level within the 100-foot cube, but not outside of that cube. (ie, the water level drops very steeply at the edge of the spell.) I would rule that the water thus created would vanish at the end of the spell.

I also would rule that a "real body of water" was required for this, such as a 20-foot-wide river or pool. If the spell were cast near a barrel of water, the barrel might overflow and cause a mess, but it would not cause a flood.

Answer 3

The limits are somewhat defined by the spell description

First off, the spell does not mention anything of creating more water, therefore we must make the assumption that the spell only work on existing water.

How much water?

According to the spell description:

Until the spell ends, you control any freestanding water inside an area you choose that is a cube up to 100 feet on a side.

Flood. You cause the water level of all standing water in the area to rise by as much as 20 feet. If the area includes a shore, the flooding water spills over onto dry land.

To find out what limitations this have, lets think out some experiments.. Here are some examples:

"Finite" volume of water in a tall container

If you have a full container without a lid that holds e.g. 50 * 50 cubic feet water and you chose to flood the cube by 20 ft, the container will first spill water corresponding to a rise of 20 ft. However according to our assumption, no excess water are created, and it is therefore not possible to maintain a rise of 20 ft, and thus the levels of spill will be reduced gradually until the water in the container until the water levels are 20 ft below the container top. (After the spell end, the levels would sink to 40 ft).

Water of an indoor swimming pool in a water proof room.

The water levels would rise up to a maximum of 20 ft, overflowing the room, however since it is waterproofed, the water would stay in place.

"Infinite" volume of water from an ocean

Making another assumption: The levels of water in an ocean are so massive, that the spell does a minimal effects on the total volume of the ocean - Therefore we can assume that the volume is infinite.

If you on the other hand stand close to the shore of an ocean, casting the spell would cause 20 ft waves to continuously once every 6 seconds, for 10 minutes or as long as you maintain concentration. This could potentially be devastating for small fisher villages, however how such cases can be resolved must be a different question.

But what happens to all that moved water?

Well, by looking at the description for Redirect flow we get an indication on how water behaves when the spell ends:

The water in the area moves as you direct it, but once it moves beyond the spell's area, it resumes its flow based on the terrain conditions. The water continues to move in the direction you chose until the spell ends or you choose a different effect.

Container

Since the water flowing out of the container are at a lower level than the top of the container, the water would start moving down terrain and stay in place (until evaporated or somehow else removed)

Pool

All of the water would seek back into the pool, leaving a huge mess to clean up.

Ocean

After the water is no longer affected to flood, it begins moving under normal conditions, as such excess water on a shore would most likely seek back into the ocean, however some of the water could potentially have filled out crevasses and thus can't escape. This could be devastating for a small village placed in a valley close to the affected shore.

One could speculate that loose objects being overflown, would be drawn into the ocean. How this would affect houses and creatures is another question (possibly at GM discretion)

Answer 4

Excess water is produced and the water spills out onto dry land as per the spells description

First we should note that Control Water is a Transmutation spell. Transmutation spells:

change the properties of a creature, object, or environment.

One of the properties of water is it's volume!

Next we need to look at the relevant sections of the spell description (emphasis mine):

Until the spell ends, you control any freestanding water inside an area you choose that is a cube up to 100 feet on a side. You can choose any of the following effects when you cast this spell. As an action on your turn you can repeat the same effect or choose a different one.

Flood. You cause the water level of all standing water in the area to rise by as much as 20 feet. If the area includes a shore, the flooding water spills over onto dry land.

If you choose an area in a large body of water, you instead create a 20-foot tall wave that travels from one side of the area to the other and then crashes down.

I've highlighted what I believe to be the key portions required to interpret this for the purposes of your question. I'll address each of them separately:

Flood.

The name of this section of the spell is flood. This is evocative of excess water covering an area of normally dry land. As a result we should be leaning towards excess water doing something in our interpretations.

Until the spell ends, you control any freestanding water

The key part of this is the phrase "freestanding water". Freestanding^{1 2 3 4}, means the water isn't supported by any external structures.

This immediately rules out the circumstances where you would "flood" a barrel or other similarly enclosed container, as the water in those containers is not "freestanding". Where the line is between "freestanding" and supported by external structures is a DM call, but water in barrels, baths or water towers are clearly not freestanding. Whether the water in a dam is freestanding however is debatable.

To further clarify this in our minds we can ask the question: If we remove a piece of whatever the water is located on/in (be it land or a container) from underneath a body of water, does it stop the body of water from remaining that body of water (eg would Lake Michigan stop being Lake Michigan if you removed a portion of land from it's shores)? The answer for freestanding bodies of water (like lakes) is categorically no. The answer for a body of water in a water tower is yes, if you removed a portion of the metal/concrete from under the water tower water it would become a series of puddles on the ground.

a cube up to 100 feet on a side

This means you can affect 1,000,000 cubic feet, or 28,316,847 litres, of water. That's a lot of water!

You cause the water level of all standing water in the area to rise by as much as 20 feet

There are two phrases we need to interpret here, "water level" and "standing water".

Standing water is water which experiences little activity or change^{5 6 (#2) 7 (adjective #3)}.

As part of your question, you asked about a river. Rivers, by definition, are not standing water as they are constantly in flux. If you think of a river, you think of a changing and moving body of water. This movement might be slow, but it is still a changing body of water. As a result, rivers aren't affected by this, unless your DM otherwise allows it.

Water level is, at is suggests, the height reached by the surface of a body of water^{8 9 10}.

So, if the body of water you are affecting with the spell is standing water, then you raise the level of the surface of the water by as much as 20 feet (suggesting choice on behalf of the caster on the precise level it is raised by). The spell doesn't say how this happens, just that it happens. So we have a couple of options:

1. The water is physically raised up to 20ft (meaning there is an equivalent gap underneath the water now)
2. New water is created because magic

We'll get back to which of those two options the rules suggest it is later, but given the name of the spell section we are looking at we should be leaning towards #1.

a shore, the flooding water spills over onto dry land

A shore is the land bordering a large body of water^{11 12 13 14}. Flooding water strongly suggests that excess water is being created in the area (at least temporarily).

Lets take the example of a puddle of water. It is freestanding, it is also standing water, as a result it can be affected by the spell. If we raise the level of this puddle by 20 ft, we either get:

1. A puddle, 20 ft in the air
2. The puddle growing in size and volume flooding an area

Given the fact that the spell says "the flooding water spills over onto dry land", option #1 cannot be the interpretation. If we insist on option #1, we would end up with the singular puddle being transformed into an expanding, ever thinner ring of water, until the water that used to be in the puddle disappears. This is not flooding water, this is puddle evaporation.

As a result we are inexorably drawn to option #2 in both of our choices. New water is created by the spell and that new water continuously spills out and floods the area until it's level can be raised to the level desired by the spellcaster, or the body of water becomes a "large body of water" of the purposes of the spell.

an area in a large body of water

What is a large body of water for the purposes of this spell?

Obviously, any body of water than can fit within the area of the spell cannot be considered large, for the purposes of this spell. On the flip side of that, an ocean is clearly a large body of water. Where the line is drawn is up the the DM, but this DM would use the area of the spell as a guide. If the spells volume can be entirely fit within a body of water (100ft x 100ft x 100ft), then it's a large body of water, otherwise it's not.

Answering your specific sub-questions

1. If you do raise the water level above the apex of its container (say a river above its river bed or a barrel of water beyond its capacity), what happens to the excess water? The spell states:
   • It floods out onto dry land, so long as the water is both freestanding and standing water
2. Does the edge of an artificial container count as a "shore"?
   • Not unless that edge also counts as "land". The edge of a barrel is clearly not land, but the side of a dam might be considered such (see Hoover Dam). Ask the DM.
3. If not, what happens to a filled container when the water level rises 20 feet?
   • If it's in an artificial container whose sides do not count as a shore its not freestanding and thus not affected by the spell unless the DM makes an exception to the ruling.
4. If it does count as a shore, does the water fill the external space 20 feet above the apex, or is the expected volume of water conserved (as if the apex had been 20 feet higher)?
   • The volume of water is not conserved, new water is created, and water will fill the external space so long as it is supported on its sides by land (or structures large enough to be considered land). For example a well containing water, you can raise the water level up to the lip of the well, before it starts spilling out and over the sides of the well.

Answer 5

To try and clear ambiguity, I'll look at this RAW (Rules as Written) and focus on option 1 of the Flood action as per your question.

what happens if the container for the water is insufficient to contain the new volume (or levitated volume)?

"Flood: You cause the water level of all standing water in the area to rise by as much as 20 feet. If the area includes a shore, the flooding water spills over onto dry land."

Shore: The land along the edge of a sea, lake, or other large body of water.

The spell does not state that having a shore is a requirement for the rest of the effect.

From the spell as written, we can therefore determine the following rules:

1. the spell will always raise the level of all standing (stagnant or still) water in the area by a maximum of 20ft
2. water will only spill over its normal boundary (sides of a puddle, lip of a barrel, edge of a pool) to flood dry land if the area of the spell contains a shore.

We can infer from this that the Flood action is only designed to simulate a flood in an area where a flood could naturally occur, such as a lakeside house.

This is similar to other control spells in the game that can have partial or no effect under certain conditions, such as Control Weather stopping early if you move to a spot where you have no clear path to the sky during the spell.

Example usage:

• Casting over an area that only contains a natural rock pool 10ft x 10ft x 10ft with 5ft of water in it - the pool will fill with water up to 10ft deep, but without a shore it will not spill over and the area around the area will not flood. (If you must go up to 20ft, I discuss that option later)
• Casting over an area that contains a portion of a dried up lake and its shore, but first you put a cup half full of water in the area - the cup will fill up and overflow, spilling over onto normally dry land and flooding the area around it to the limits of the spell. (And before you ask, no I don't think it's overpowered having a 4th level spell make a 100x100ft area wet, the 1st level spell create water cast in a 4th level slot could already do 45x45ft of that anyway)

Just because you can cast a spell in an area doesn't mean it will attain its maximum potential. (You could raise a fireball to 9th level and blast the last 1hp off a Goblin, but some people might think that's an ineffective use of the spell)

To me, this also sounds like RAI (Rules as Intended) for the spell.

Some people were concerned with what "freestanding" means - ultimately that has no impact on the spell effects based on this interpretation; it's just whether your DM really wants to make you tip the water out of the barrel before you cast the spell or not.

To answer your other questions briefly:

Does this create new water, or simply levitate the water already present?

Transmutation is all about making something from something else. There are many arguments going around saying that is not creation and I won't go into it here, but simply put you are transmuting something (either the spell components, energy, the air, or whatever you imagine) into as much water as you need for the spell. The end result is you have more water than you started with. To me that's textbook "creating" something, but for the spell it doesn't really matter what you call it.

Why is there more water? Because the spell, ruled as written, does not change any dynamics of the original body of water for the flood effect; you can still swim in it normally, you don't fall 20ft through a pocket of air between water layers, etc. I also believe that would be the RAI reading.

Can it be used to target an artificial container?

No - you target an area. That area might have an artificial container with water in it which then might be affected by the spell depending which option you choose.

Does the edge of an artificial container count as a "shore"?

No, but you are welcome to say it does at your table. Maybe you're all playing a race of tiny ants and it makes sense that the edge of a container is as close to a "shore" as the beach would be for humans.

If not, what happens to a filled container when the water level rises 20 feet?

Either

1. It does not rise 20ft and stops at the top of the container, or
2. Similar to the "Part Water" option for the spell, the water level will rise 20ft up from its original level, but be walled in and not spill over to dry land. This would look pretty funny/silly/definitely cool, but ultimately doesn't have a massive impact on the game other that you could use a 4th level slot to cast something similar to a 3rd level wall of water (I think this is a totally valid interpretation).

If it does count as a shore, does the water fill the external space 20 feet above the apex, or is the expected volume of water conserved (as if the apex had been 20 feet higher)?

The spell states the water level will rise and spill over onto dry land, so it will not fill any space above the container; the dry land area in the spell will be covered in water and become wet for the duration of the spell or until you choose another option, in which case the level returns to normal and the land dries out until you choose the "Flood" option again. (If the water simply levitated, or more water was not created to increase the water level, then you would not be able to maintain the flood option each round as the water may run out before the spell's duration ends)

I think there is also an implied question here of:

I'm an evil Wizard who makes 20x20x20ft rooms out of one-way mirrors so I can see into it from the outside, can I use this spell to drown people I trap in there?

Using what we discussed here, not unless your table allows the Part Water/Wall of Water like use of the Flood option and the floor is already covered in water, in which case sit back and watch! Mwahahahaha!

Answer 6

The water flows out of the container

You cast Control Water on a barrel of water, selecting the Flood effect:

Flood. You cause the water level of all standing water in the area to rise by as much as 20 feet.

...

The water level remains elevated until the spell ends or you choose a different effect.

The lip of a barrel is not a shore. The barrel is not a large body of water either.

The water level of the barrel rises by as much as 20ft, immediately the water spills and flows out of the barrel as normal water would. There is no additional special effect. You can visualize a 20ft column of water spouting from the barrel, and water consequently pouring everywhere.

Once the spell ends, the water transforms back to its original form. There is no description of what exactly this looks like.

Answer 7

Control Water does not create additional water.

First, the spell Control Water does not create additional water, which is evident when you look at each of its effects, and the spell Create or Destroy Water.

Control Water states

[...]you control any freestanding water[...]

and makes no mention anywhere of creating water(as opposed to the Spell Create or Destroy Water, which explicitly says it does create more). The only statement within the spell that even comes close is

You cause the water level of all standing water in the area to rise[...]

however, water level is simply the height of the water's surface, which can be raised by anything that increases, displaces, or lifts the water. If you look at each of the other options for Control Water, they only move water within the target area (parting it, changing its flow, or making it spiral). Since nothing within the spell speaks of creating more water, the spell cannot be considered to do so by RAW.

Water within a container is not a valid target for Control Water.

Containers have no definition within 5e, so we have to turn to the dictionary.

Merriam-Webster defines a container as "one that contains, such as 'a receptacle (such as a box or jar) for holding goods'". As boxes and jars are similar to known containers within 5e, they would be Objects, which are not part of the land.

Further, Control Water's Flood option gives 2 different effects, depending on where it is used:

If the area includes a shore, the flooding water spills over onto dry land.
If you choose an area in a large body of water, you instead create a 20-foot tall wave that travels from one side of the area to the other and then crashes down.

So we need to define 'shore'. Merriam-Webster defines shore as "the land bordering a usually large body of water".
Which leads us to defining 'land':

• the solid part of the surface of the earth
• ground or soil of a specified situation, nature, or quality

As a container is not part of the soil (earth), it cannot have a shore, so water within it cannot be a valid target of the Control Water spell.

Finally, given the meaning of 'shore', and that both flood effects effectively refer to large bodies of water, it seems clear that a large area of water is the intended target of the spell, even though no minimum size is given within it.

As to what happens if water rises high enough, that is stated in a quote within your question:

[...]the flooding water spills over onto dry land.
The water level remains elevated until the spell ends or you choose a different effect.

So water that rises above a natural boundary spills over, and water not within the affected area (either due to the effect ending, or it exiting the area) responds to the environmental effects as normal, flowing wherever gravity directs it.

Answer 8

First and most importantly, the "Control Water" spell does not create more water.

"Until the spell ends, you control any freestanding water inside an area you choose that is a cube up to 100 feet on a side."

The spell then gives you four options that you get to choose on each of your turns as well as the turn that the spell is cast as long as you maintain concentration. Those options are "Flood", "Part Water", "Redirect flow", and "Whirlpool" When read fully, none of these options actually create more water than what was originally there.

I start out with this because your main question "what happens if the container for the water is insufficient to contain the NEW VOLUME?" (all caps the part I am first addressing) implies that you can create more water with the "Control Water" spell, which you can not.

2nd, Now as far as the Flood option, lets dig in. Flood gives you 2 more options based on the area of water you are controlling. You can either cause the existing water to rise 20 feet up (so you could say safely allow your fellow party members to scavenge the bottom of a body of water) or IF you selected a large body of water you can create a 20ft tall wave that then crashes at the destination of your choosing (Fun for naval fights)

Now as you pointed out "If the area includes a shore, the flooding water spills over onto dry land." If you keep reading 2 paragraphs down it then says "The water level remains elevated until the spell ends or you choose a different effect. If this effect produced a wave, the wave repeats on the start of your next turn while the flood effect lasts"

Conclusion

So it is up to your DM to define what shore is in his/her campaign however generally speaking I would say that the only case in which the water would spill over when originating from an artificial container is if you raised water from say a marine tank like the kind in our world designed to hold killer whales, manatees, and other large marine life forms. The reason as to why I say this because due to the limitation of "cube up to 100 feet on a side" you can control up to 7,480,000 gallons of water at a time since there are 7.48 gallons per cubic foot. (equation pulled from https://sciencing.com/calculate-water-fill-rectangular-tank-7686198.html)

When the water is elevated, the container previously holding it becomes empty. If the container still has water in it when you choose this effect the remaining water inside the container would level itself out. So to address your examples, water from a barrel would remain elevated, the river would flood onto the land and soak itself into the ground as water from upriver would then refill the space shortly afterwards, if the edge of an artificial container counts as a shore then when the flood option is chosen the water being controlled will come crashing down onto "shore" and the remaining water in the container will level out, if the edge of an artificial container doesn't count as a shore then the water remains elevated and any remaining water levels out in the container.

I'll gladly clarify anything that doesn't make sense in my answer.

Answer 9

1. I think those getting caught up on whether it creates water or not are missing an important factor. This is a transmutation spell. Conjuration magic can summon something from nothing. Transmutation cannot. However, if we look at another transmutation spell, Polymorph, for reference, it can turn a t-rex into a toad and vice versa. Or stated another way, it can take a volume of existing mass and change it to a different volume of mass. Using that demonstrated ability, I would think that Control Water could take an existing volume of standing water and change it to a different volume of water.

2. This also fits with "Until the spell ends, you control any freestanding water inside an area you choose that is a cube up to 100 feet on a side." You are controlling all of the existing freestanding water inside that up to 100 ft cube and changing its volume with transmutation magic.

3. "If the area includes a shore, the flooding water spills over onto dry land." I think this describes how gravity and the rest of normal physics are still affecting the water. It does not raise straight up in a column from where it starts with magical force restraining it in a straight-walled container. Instead, as the water level rises and reaches the edges of its natural container (the shore) it spills over. Using this logic, I would think that the water would indeed spill over the edges of whatever container it is in.

Side note: as it is written, Control Water cannot flood a river or stream, as that is flowing water. It specifically says that you can flood standing water or direct the flow of flowing water. My interpretation of this is that flowing water has a place to go, so you can try to use Flood to increase the volume of that stream or river, but the water keeps flowing, albeit at a somewhat faster pace. Now, if the flow was somehow blocked or restricted, I think that could change things and it would be a call for the DM to make as to what happens if you try to flood it.