True, but rough mounding is a legit strategy for retaining water and creating microsites for plants in non-desert climates. Here, it needs a bit more help to get established. I suspect once it reaches a certain threshold, water inputs would be reduced.

Not everything is irrigated. They showed areas that are only fed by rainwater.

I think the point is that the soil was swept away and the ground is impermeable so any rainwater flows into the river or evaporates rather than supporting plant life or replenishing the groundwater.