I'm not a Bitcoin fan, but it's still an asinine comparison. Visa merely records the transaction, whereas crypto secures it. How much energy does everyone from Visa's fraud division to the US Secret Service spend to secure credit-card transactions?
No. Visa also secures data in transit via whatever algorithms they use. Practically all websites that handle money shifted to TLS encryption, and I'm pretty sure they practice all that infosec voodoo for their servers.
Regulatory anti-fraud activity would also apply to crypto. The notion that crypto is fraud-proof can easily be proven false by looking at your email's spam folder and counting the phishing campaigns received. Or better yet, the number of crypto stealing malware that have been popping up in the last decade.
It has no hydroelectric plants either, but that didn't stop the study authors from using the vastly higher evaporation figures for hydro reservoirs to calculate water usage.
They actually do. A fraction of the total generation, but still.
Have you actually read this study, by the way? To quote (with emphasis):
Hydropower generation generally consumes even more water per kilowatt-hour (kWh) generated, as water evaporates from the hydropower reservoirs. However, these reservoirs may serve purposes beyond electricity generation; thus, this commentary considers only the portion of water loss attributable to power generation.
They also do explicitly state the minor role of hydro in the total budget.
But it still precipitates somewhere. This study attempts to cast the usage as a global problem, when the facts are otherwise. Either the so-called "consumed" water returns as additional precipitation to the same region, meaning it changes nothing; or it precipitates elsewhere, meaning it actually alleviates a local problem there.
Roughly three quarters of global precipitation occurs over the oceans. And even precipitation that occurs over land, only part of it accumulates in a usable form. Can be as low as 10~20% for surface runoff (streams, etc). What little gets to infiltrate into the soil can't be fully accounted for either. Top soil moisture is unharvestable and will be lost to evaporation (or rainfed agriculture and natural flora, but they would probably be insignificant compared to the total volume of soil moisture, especially in regions such as Kazakhastan). Deeper flow can take a long time to reach aquifers, and aquifers themselves can't be fully drained (and have strict limitations to how fast you can abstract them).
Total water content in the planet may be fixed, but much like energy we describe as entropy, not all of it can be used.
And I'm skipping over the issue of trans-boundary water resources and the losses within these systems here.
To further show how absurd this methodology is, these studies calculate hydroelectric as by far the largest consumer of water per MW-hr. But unlike other electricity sources, evaporation from a hydro reservoir doesn't increase as more electricity is generated; it actually declines slightly. (the reservoir level drops). Also, the studies assume that the only purpose of a hydro reservoir is electricity generation, when most of these would exist regardless -- nearly all dams are built to control flooding, manage water levels for irrigation and navigation, etc.
Skipping over the already addressed "what dams are" for part, I want to point out two issues in this paragraph (that may be slightly unrelated to the exact topic at hand):
For multi-purpose reservoirs, releasing water for power generation does indeed reduce evaporation. But the water released would be unavailable to the other consumptive purposes (irrigation, domestic, etc) of said reservoir.
Multi-reservoir systems make the situation even more complex. You can't just release water at will. Although, I admit, the issue here becomes less of water waste, more of energy generation limits.