I get out when it's raining and see where the water is and make small trenches until it flows, then grass them up, then next time it rains I get out and adjust it again...
And I have holes dug around the garden so I can monitor the water levels.
The rain water used to drain from the previous owner's well manured flower bed in through the air bricks and under the house!
[g]
The chances are that a spring in sloping ground is a seepage spring, which is fed by water flowing downhill through the earth until it reaches the point at which there is so much water it cannot stay underground. Stop water feeding it and it will stop flowing. Of course, if it is a fracture spring, discharging from a crack in underlying bedrock, you won't be able to stop it.that way.
The practicality of putting in the necessary drainage is another matter, which only you can judge.
Colin Bignell
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