Someone just asked me if it would be practical to counter the rise of sea level by pumping water into storage on land. It struck me that if there is enough land below sea level, this would require construction of aquifers, but would not require using energy to pump the water as the destination of the water would be below its current level. But I have no idea how much land below sea level is available.
This question is intriguing. At the current rate of sea rise (about 3 mm per year), all of the Earth's dry land below sea level would be submerged in just a decade. There are an estimated 49 countries around the global with at least some real estate below -0- metres elevation, but the sum of all the potential volume (around 7,500 km^3) is insignificant compared to the volume of water generated by glacial and ice cap melt: "A meter of sea level rise is a volume 50 times greater than all of the depressions that are below sea level in the world", according to this link: http://mountainmystery.com/2015/08/17/hiding-rising-seas-in-sunken-deserts/.