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I have Macro question, and have enquired and discussed this topic with numerous people. My background is more in Economics and Finance, but I have a small little plot in the Waterberg Limpopo (Pecan and Cattle) and read a very interesting article if I am not mistaken 10-15 years ago in the Farmers weekly of a WITS Geography professor who did a study in +-1905. Much of the article had to do with energy and the amount of energy used for cloud formation and movement from the Coast into the central parts of Southern Africa. Energy at the time I assume was a "buzz topic" as Electricity was in its early stage.

The Professor had, among others, identified a location on the Zambezi where the Zambezi and Chobe rivers (coming from the Caprivi) meet +-40km upriver from the Vic Falls, I assume close to the newly built Kazungula Bridge?

In essence the suggestion was that by the construction a 14 meter high, controllable weir, in times of flooding the river would be able to flow along the ancient route, filling Lake Liambezi, and pushing back to Maun and back via the Boteti river ultimately filling the Makgadikgadi pans.

Building a 14m high Weir 900m wide using human and animal labor was an immense challenge 120 years ago. With modern earthmoving equipment such a task would be like building a "big farm dam"!

My question and thinking - this would create MASSIVE "evaporation pans", which would in turn raise the rainfall in especially the winter months in much of the Northern Cape, and especially Botswana moving over to Limpopo province, and ultimately raise the Average Rainfall throughout the entire Southern Africa by rough calculations 100mm-200mm per year.

I assume in the 1900's many studies were done on energy rather than Water supply, with considerably lower world populations at that time.

Today Climate change and its consequences are some of the biggest challenges facing Humanity.

By Ultimately raising the Rainfall in the entire Southern Africa, through the managed and controlled filling and utilization of the Natural 30 000 - 60 000 square km of evaporation pans more regularly, will this not lower the extreme temperatures and drought patterns Southern Africa has experienced, and by all predictions are bound to worsen and could become more extreme?

A study of such a magnitude will need much research in multidisciplinary sciences, from Archaeology to Agriculture to Economics, and a much broader field of expertise.

Could such a mammoth project not be but one small answer to a much bigger Climate Change challenge facing the Earth? (and ultimately send a bit of rain to my little farm in the Waterberg in the long dry winter months when we receive those dry West Winds - (simply by adding a bit of moisture from the vast pans Botswana are so blessed with!)

My mind has been going in circles as to the feasibility of such a mammoth, yet so cheap and easily implementable idea?

Any ideas?

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    $\begingroup$ Here is a map of the Arabian Peninsula. Notice the two gigantic evaporation pans labelled the Red Sea and the Persian Gulf. Right between the two lies the Arabian Desert. Long story short, evaporation is only the first part; you also need to convince the vapor to condense into clouds and then the clouds to rain down. (And oh how beautiful is Waterberg! Thank you for making me discover such a marvellous place.) $\endgroup$
    – AlexP
    Jun 12, 2022 at 21:25
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    $\begingroup$ P.S. Isn't there already a very large evaporation pan in the area, called the Okavango Delta? It evaporates 11 cubic kilometers of water per year; and it is arranged so that maximum evaporation happens between June and August. $\endgroup$
    – AlexP
    Jun 12, 2022 at 21:40
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    $\begingroup$ Is this a worldbuilding question about a fictional world, or a real-world question? The former would be on-topic, the latter - fascinating and worthwhile understanding, but off-topic. Could you clarify. $\endgroup$ Jun 12, 2022 at 21:46
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    $\begingroup$ @JiminyCricket. - I think this is imagining a world that could be, starting with the world we have and using the rules of what is real. Real worldbuilding! The trick here will be finding the report from 1905 as back reading. $\endgroup$
    – Willk
    Jun 12, 2022 at 21:59
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    $\begingroup$ I’m voting to close this Q because it's a real-world question for real-world purposes. The help center states that ours "is a site for designers, writers, artists, gamers and enthusiasts to get help creating imaginary worlds." Even if you spin this as alternate-history, it's still a real-world problem. Why didn't you ask this on Earth Science? (In other words, the only practical answer here is "yes! it's your imaginary world and your rules, so you set the economics and geopolitical parameters, of course you can do it!") $\endgroup$
    – JBH
    Jun 13, 2022 at 4:59

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Your project is interesting, but must compete with other water uses

To begin with: this is a forum for fictional worldbuilding, so I'll speak even though I'm not a real-life engineer. You'll probably need a higher-grade forum if you want higher-grade answers.

The first problem you have is that the Zambezi River, though mighty, is not boundless, and you can already see Wikipedia's summary noting the negative effects of two existing dams on mangroves and coastal flooded savanna. Authorizing this project would have a measurable environmental cost, and would likely mean denying some other project in the future.

The big problem I see is that you're thinking of flooding salt pans with the water. To begin with, salt pans can be trouble - the Great Salt Lake is beginning to go the way of the Aral Sea, meaning the emission of large amounts of dust that includes whatever contaminants washed in with the water. The Salton Sea illustrates that a short period of flooding, followed by a change of heart, equals trouble. With such precedents, the government of Botswana or any other country had better think really hard before they commit to flooding a salt lake.

Additionally, sending the water to a salt pan means not using it for conventional irrigation. Why not build an ordinary irrigation system that divides up and ends at farmland? The water will still evaporate when the plants are done with it.

Then there's the issue of nationality. I see Botswana has access to only a small portion of the river, though I know nothing about water rights agreements. Can they get anyone to cooperate in a plan to divert water?

Now for purposes of fiction, you can suppose someone with money is behind it and they lobby hard and miracles can happen. There are precedents for dams on the Zambezi, and for water flow between the Okavango and the Zambezi (but in the other direction). Still, it's hard for me to see why that isn't going to lead to a large privately owned pipe delivering to paying customers.

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  • $\begingroup$ Brilliant, thanx a million - Salt pans- never thought about that? Your scope of knowledge amazing! $\endgroup$ Jun 13, 2022 at 7:30

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