What would cause a large & long lasting regional increase in rainfall?

Question

So after the answers on my last question, I got some very useful information about why the idea in the question wouldn't work. I looked into it more and figured that the best solution to the problem would be a significant increase in rainfall.

To @KerAvon2055’s point, if the lake is drying up from an outflow increase, then a recent severe inflow increase would mean that the lake is now overflowing with water. This would require an additional way to reduce the inflow to keep the surrounding area from, well, flooding.

For the process taking an extremely long time brought up by D'Monlord i found 2 things:

• Residence time is mostly a function of inflow vs volume.
• The Aral sea which this endoheric lake is based on surprisingly had a residence time of 19.6 years in comparison to the comparable but larger Caspian's 250 year residence time (before it largely dried up).

This means a large increase due to inflow could realistically bring the replacement time down to a level at which it would only take 1 or 2 decades for the surface areas of it at least to be brought down to a drinkable level of saltiness. (i think).

But now the problem is how to cause that recent rainfall increase. It's seemingly quite difficult for me to find information on this because most of what comes up is information about global warming.

The climate of the area where the lake is located is primarily a hot and arid BWH climate, similar to the Outback of Australia. This is created by a rain shadow cast across ~100-200km wide sea from the east, the area being close to 30 south, & a cold current running off the east coast. The rivers that provide inflow originate in an area north of the desert with an Af tropical savannah climate on a pair of large peninsulas, beyond the rain shadow of the mountains. The rivers flow south across the desert into the inland sea, roughly in the center of the rain shadow. The increase in rainfall would be happening around where the rivers originate the north, i want the desert to remain a desert. The geography elsewhere can be whatever needed.

The increase in rainfall has to be (relatively) quick, taking a few years at most for the increase to take effect, & it has to last a reasonable time, preferably at least a century or two, while being a 25% or more increase. The climate elsewhere can be somewhat affected, but it cannot be cataclysmically affected.

What could create a lasting significant increase in rainfall in the environment specified above?

Answer 1

Little frame chalenge. Do not focus on rain, focus on water sources. Here have some:

1. volcano - long lasting not too intensive erruption - more water agregation particles in air leads to more rain. Volcano can last up to couple hundred years.
2. forest/wild fire - short period - like weeks but can make intense rain.
3. glacier - glaciers are slow moving but small earthquake can make one to move fast like avalanche - then it will melt faster and give more water for months and when extra large one even for decades.
4. earthquake - can rise ground enough to redirect a river who was going to another lake/sea to Yours one.

Answer 2

Human Intervention

The industrial revolution came with the burning of massive amounts of dirty fossil fuels. One of the big byproducts of burning large amounts of low quality petrol, coal, etc. is that it dumps tons of sulfur into the air. Sulfur is a known cloud seeding element meaning that it draws otherwise evenly distributed moister from the air together to form thick clouds which increases rainfall.

So, if your northern territory began its industrial revolution a few hundred years ago, all those smoke stacks from the factories would cause the region to experience more rainfall while the desert which does not have factories would experience equal, or possibly even less, rainfall as a result.