A different question, but I'd like to know how much rainfall those poplars
need, esp if the water table is too low to help.
That is the situation mine are growing in, low water table but rich soil, well
drained. Mine are planted midway along a long slope so they get a lot of
runoff; this is why I suggested planting them above a swale or berm on a
slope.
If on flat ground build some sort of earth containmant to catch runoff and mulch
well. My impression is that poplars are somewhat drought resistant if they are
surrounded by plants providing shade, to increase soil moisture. They are very
vigorous growers and I would recommend planting them for shade, windbreak,
nectar for bees and ornamental landscape purposes. So what if they lack moisture
to grow large, they will still serve a very useful purpose. I would interplant
them with cedars, eleagnus, blueberries, comfrey with clover and low weeds for
ground cover within deep mulch.