Most land based plants would die if fed saltwater.
The water would in most cases sink away below the surface too.
While that's true, a large saltwater deposit somewhere arid would allow for water to evaporate into the air and create humidity and increase the probability of rain occurring in that area regularly.
If by "large Saltwater deposit" you mean "an ocean" then maybe. Pumped sea water? No.
Is rain, too, not salty?
Compared to a river, yes. Compared to the ocean, no.
Rainwater typically has a TDS of 20 mg/L or less. Fresh water from lakes, rivers, and groundwater is more variable, with TDS ranging from 20 mg/L to approximately 1,000 mg/L. Brackish water is, by definition, water with TDS exceeding 1,000 mg/L and ranging as high as that of seawater, at approximately 35,000 mg/L.
Most land based plants would die if fed saltwater.
The water would in most cases sink away below the surface too.
While that's true, a large saltwater deposit somewhere arid would allow for water to evaporate into the air and create humidity and increase the probability of rain occurring in that area regularly.
If by "large Saltwater deposit" you mean "an ocean" then maybe. Pumped sea water? No.
Is rain, too, not salty?
Compared to a river, yes. Compared to the ocean, no.
https://watereuse.org/salinity-management/ls/ls_3d.html
No. The salt gets left behind when water evaporates.