In 1965, the federal government dammed up a river to create Lake Meredith in Texas. It’s a reservoir that provides drinking water to 11 cities, and locals use it to swim and boat and be outdoors, as well, Next City reports. But it’s been shrinking, as you can see in the video below. The time-lapse begins in 1984, with a full, deep lake, and it ends in 2012 with a stub of water.

Why’s the water disappearing? Many reasons, Next City says:

One study found that there was no single factor causing the lake to disappear, but rather a combination of contributing factors, including a decrease in significant rainfall events that generate runoff and a precipitous decline in groundwater levels. The spread of brush, especially the water-hungry salt cedar, is also considered to be a likely contributor.

In other words, the environment is changing, and much of what we’ve come to take for granted — clean water to grow food in dry places, lakes to swim in and skim over on jet skis and kayaks and rowboats — won’t necessarily be there when we need it.

See: