Name him Asshole. He should dig down till he is next to a (See bottom of post) murky pool like this.
~||||||D|...|
~~~~CF......|
~~~~|||W|...|
|~~~|||X|||||
Where X and Up/Down staircase, | is natural wall, W is a drawbridge that raises up, . is open ground, F is floodgate, C is a tile you channel from above, and D is a door. See plans below for main fort.
|||||X|||||||
||TCD.DB|||||
|||||D|||||||
||SSS..L|www|
||SSS....www|
||SSS..L|www|
||WWW..L|www|
||WWW..L|www|
||WWW..L|CCC|
||MMM..L|CCC|
||MMM..L|CCC|
||MMM..i|||||
~||||||D|...|
| is natural wall, M is masonry, W is mechanic's workshop, S is a still, C is a carpenters workshop, w is a wood stockpile, L is a lever(unconnected), i is a lever linked to the floodgate by the pool, . is floor, D is a door, T is a table, C is a chair/throne, B is a bed, and X is an Up/Down staircase escape route to the next z-level up. The last row is the top row of the entrance.
Don't let any other dwarf in this area, but let Asshole move across the entire camp. Once all this is mined out, pull the floodgate lever. Once the farm space has water in it, pull the floodgate closed. Let the water evaporate, destroying water by opening the floodgate, then closing it once water is on the tile if need-be. Once the water is gone or down to a patchwork of 0/7 and 1/7, plop down a 3x3 plot of farm, setting plumphelmets to be grown there. Once some are fully grown and the wood stockpile is half full (Asshole can chop down trees if he needs to, and you can set the pile to take wood from the main wood pile), send Asshole down there, link up the top lever to the drawbridge, and pull it. Make two or three barrels and fill one with booze from the still. Make more booze as needed until the end of the season, while keeping Asshole farming. If you don't get any migrants during Spring, do this in Summer. If you don't get any migrants in Summer, do it in fall. Keep bumping it back a season until you get migrants.