It's hard to overstate the magnitude of the flooding that's hit Texas recently. The Memorial Day weekend of heavy rain has capped off a month where some areas of the state have seen more than 20 inches of rain fall. More rain is in the forecast.

It's difficult to comprehend the ridiculous amounts of water that have fallen in such a short time in a state that, until recently, had been in the grip of a historic drought. But one place to start would be to look at reservoir levels in the state. In the past 30 days, Texas reservoirs have gone from being 73 percent full to 82 percent full, according to data maintained by the Texas Water Development board. All told, about 8 million acre-feet of water have flowed into the state's reservoirs.

But how much water is that, even? An acre-foot is the amount of water it would take to cover one acre of land in one foot of water. It's the unit the government uses to measure things like lake, river and reservoir capacity. If we were to take all of that water and put it in a cube, that cube would be about 35 feet long on any side. Here's what an acre-foot looks like with a 6-foot tall human next to it, for scale.

Quite a bit, isn't it? Just eyeballing, it looks like enough water to completely fill up a good-sized house. According to the EPA, the average American family can expect to go through about half an acre-foot of water per year.

But this is just one acre-foot, and in Texas we're talking about millions. So let's bump up the scale.

In this view I've multiplied that cube by 1,000. Now we're looking at an enormous block of water 351 feet long on any side. By comparison, the Statue of Liberty is only about 305 feet tall from ground to torch. A person is barely visible in this view. With 1,000 acre-feet of water, you could fulfill the water needs of a 2,000 household town for a year, or fill up about 500 Olympic size swimming pools.

But we're still not at the right scale to understand Texas. Let's cube it again:


Now we're getting somewhere. Each one of these cubes is 1,000 acre-feet in size, for a total of 1 million acre-feet. The Burj Khalifa, the world's tallest building at 2,700 feet, is dwarfed by this massive brick of water. The Statue of Liberty is just a speck at this scale.

This 3,500 foot tall block of water could supply the needs of a city of 8 million people for one year. The crazy thing? This all flowed into Texas reservoirs in just the past 48 hours.

But those 48 hours are still just the tip of the iceberg in terms of the rain that's fallen in the past month. Finally, here's the full block of 8,000,000 acre-feet of water that's accumulated in the past 30 days. With that much water you could put the state of Rhode Island under 10 feet of water. You could meet New York City's water needs for seven full years. You could nearly double the volume of water currently in Lake Mead, the largest reservoir in the U.S.

So you can start to see the magnitude of crisis that Texas is facing. But even this is just a fraction of the total amount of rain that's fallen. After all, much of the rain doesn't end up in reservoirs, but soaks into the ground or runs off from rivers to the sea. And this doesn't even count the amount of water that's fallen in Oklahoma.

And most troubling for people on the ground in those areas: there's more rain in the forecast.

Bryan Rumbaugh used a drone to film the flooded Buffalo Bayou after nearly 11 inches of overnight rainfall in Houston. (Bryan Rumbaugh)