Improving the navigation of a river

So, the campaign I am currently in is set in Normandy Tribunal, and one of the players is from that part of Europe. When we discussed traveling down river, he asked what time of year it was, apparently in the spring and fall the river is high enough for travel, but in the winter and summer, it is not.

So, driving home from the game, I thought to myself, “How hard would it be for a Hermetic Magus to fix that? We got Aquam vis.”

So, base difficulty for filling a container with water is 2. Base size for water is a pond, which is bigger than any container I am considering building. I am considering a barrel of about 100 gallons. So, I build this effect into a 100 gallon barrel, with Touch range, moon duration, target individual and unlimited uses. Only a Level 20 effect. Then I build the barrel so that it tips over when full, tips back upright when empty and is triggered when it is upright.

So, questions

  1. How would I figure out if I am adding enough water to enable navigation? A lot of it depends on how steep and wide the river is, but if I knew these things, how would I figure it out?
  2. What is the downside to the river of having large amounts of water disappearing every full and new moon?
  3. No one did much irrigation from the river in 1222 France, right?
  4. This is in the Normandy Tribunal, which mostly takes the position that only when other magi are inconvenienced that interfering with mundanes is a problem. However, there is a canonical covenant (I think it is called Nici, but serf’s parma) which lies just downstream of us. I think as long as we negotiate with them about it before hand, they probably would be OK with it, as it would encourage trade in their area, but what reasons might they have of complaining?

Let's take a minor river like the Charente.

It is barely navigable, and has an average discharge at the river mouth of 40 cubic meters of water per second. Your hypothetical barrel-tipping-device would add a bit below one cubic meter of water (one cubic meter = 264 us gallons, google tells me) every few seconds. It wouldn't have an appreciable effect.

I'd suggest a scaled-down deluge of rushing and dashing (CrAq 40) instead. Base 5 instead of 10, but keep the +3 for size to affect the whole stream. Rather more ambitious, true, but making a constant effect magical device would fix it properly.

Imagine if the early Order had helped Charlemagne succeed in connecting the Rhine and the Danube.

I think something along the lines of Base 5, a high flow rate spring and +2 Size added to that, Month +3 Duration...
That should be adding something like 250-500 cubic meters of water per Round, so 40+ cbm per second.
Its a level 30 item to make, not beyond a skilled magi´s ability to do as a Lesser Enchantment(maybe with a bit of help and an improved lab, but still not outrageously high).

Of course, raising the water level doesnt make a river easy to travel just by itself. You will probably need to have a magi or two travel along the river, removing obstacles and making sure things are fine, like river banks that wont break or lacks room for overflow.

You can also make the river useful for travel by simply "cleaning it up"(as above) and then adding a small number of canal locks to make sure there´s always a high enough water level in all parts of the river.

Oh, pretty picture of the remains of the canal there.
And the idea is neat. Landscaping can change history A LOT. :smiling_imp:

And as it was the digging that was the big problem with building canals, and thats the easiest part for magi to handle, almost any covenant that wants to could probably build canals almost as they want. Of course it would still take quite some time ot build, but only a tiny fraction of doing it manually, not to forget the ability to build it in ways normally nigh-on impossible, or extremely time consuming or hard, like going through a mountain...

Personally, I do not think that adding more water is the way to go if your purpose is to make a river navigable; adding more water might make the river flow faster without rising its level appreciably; it might make it overflow in some places, causing damage; and so on. By the same token, if you slow the river, you can make its level rise even without increasing the total flow of water.

Thus, I'd suggest using the level 1 Rego Aquam guideline, "Control a liquid in an extremely gentle way". You need a Group target to affect a whole large river; this controls a section of the river about two and a half paces deep on average, 40 paces across, and 5 paces long (ten times the base individual). Of course, if the river is twice as wide or twice as deep, you'll get half the length etc. As they say, Your Mileage May Vary :smiley:

So, you need a lot of extra magnitudes for size! At the width and depth above, it's 5 magnitudes up to 300 miles or so (I doubt there's anything longer than that and not naturally navigable). Thus you can make navigable a river, that is 300 miles long, 2.5 paces deep and 40 paces wide on average, with the following effect instilled in a magic item:

The Riverman's Blessing
Rego Aquam 39
Base 1 "Control a liquid in an extremely gentle way", +1 Touch, +2 Sun, +2 Group, +5 Size, adding 4 levels for 2 uses/day and an environmental trigger (Sun duration, 2 uses/day and an environmental trigger Sunrise/Sunset is the way to make a "permanent" effect, according to the corebook).

Ultimately, since every magnitude is a factor 10, the final effect is not going to vary so much; for example about 2 extra magnitudes are enough to encompass the Rhine, which is about 2.5 times longer, 4 times deeper, and 10 times wider.

RoP: Magic , page 43: Atlantean Magic (Minor , Hermetic)
Water-way (Range) : +03 as for Sight
[b]Body-of-water /b : +03 as for Structure

The descriptions in the book give clarifications on Range and Target.

That would certainly be a handy Virtue to have for this purpose.
I've still not found a single player who's had his character take it, though.

Crest of the Earth Wave ReTe Level 20 , page 156 (ArM 05)
Push of the Gentle Wave ReAq Level 15 , page 124
Waves of Drowning and Smashing ReAq Level 30 , page 124

Crest of the River Wave
ReAq Level 35
R: Voice , D: Sun , T: Part

Creates a wave in the river beneath the prow of a ship you are standing on ,
that travels out to the range of your Voice in a designated direction.
It starts as a small , curved wave and grows for the first 10 paces , reaching its full size of 5 feet high and 30 paces wide.
It moves at 50 paces per round.
Unlike the Terram spell , this wave is designed for movement , not damage.

Base 04 , +02 Voice , +02 Sun , +01 Part , +02 Size
(page 124) Level 04: Control a liquid in a forceful but calm way , such as a fast but constant current.