Error on large water balance error

[visr]

What
If the water balance error exceeds a certain fraction, we want the simulation to stop with a clear error message.

How
We should probably add a solver option for this with a reasonable default fraction like 0.01.

Additional context

• Error on fixed dt leading to negative storage #1406 is a similar error that we should also throw at runtime.
• Add remaining water balance terms to basin.arrow #1367 calculated the water balance error for the results, after the simulation finished.
• Show convergence bottleneck nodes to users #452 is relevant for pointing to the problematic nodes in an error message.

[evetion]

We could consider implementing a continuity tracer for this (which gives a fraction around 1 per basin?) as well during the run?

Or did you plan on moving the logic in #1367 to a callback?

[visr]

Yeah the latter.

[visr]

Done in #1819, in the function check_water_balance_error.