Such aquifer draining structures (quanat) would result in dry climate over time, much like we see in Iran. Deep rooted plants - trees, perennial grasses - would no longer get water from the drier aquifer.

In contrast, aquifer recharging systems (amunas, swales) tens to create a wetter climate over time. In addition to the plants using water themselves, some trees also create aerosols that cause more rain. Very special trees - such as redwoods [0] - can directly capture moisture from fog, that would otherwise never fall as rain. .

[0] e.g. "Foliar water uptake: a common water acquisition strategy for plants of the redwood forest" Limm et al., 2009 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2727584/