Arthur Smith, as his wont, raises an interesting point at Not Spaghetti about a stopgap for handling sea level rise
. . . there may be something much simpler we could do that would not require huge energy expenditures in itself: retain more of the naturally precipitated water on continental land. Annual precipitation depth over most land areas of the world is on the order of 1000 mm/year. If we just divert 0.3 to 1% of that rainfall to prevent it from returning to the world's oceans we could stop SLR until whatever storage capacity was involved became full. This could have significant additional benefits. Increasing the world's reserves of fresh water could help alleviate the droughts expected under climate change. Large water reservoirs close in horizontal distance but significantly separated vertically could provide new pumped hydro-electric energy storage that would be the perfect complement to increased solar and wind resource use. Refilling underground aquifers would reverse the salt-water incursion and stop the land subsidence problems that have plagued some parts of the world in recent years. What are the potential total capacities of these systems?Indeed, BF Chao has long been on the track of the effects of sea level of both impoundment and depletion of water resources on land. The effect is large, and indeed has had measurable consequences on the observed sea level rise.
a total of ~10,800 cubic kilometers of water has been impounded on land to date, reducing the magnitude of global sea level (GSL) rise by – 30.0 millimeters, at an average rate of –0.55 millimeters per year during the past half century. This demands a considerably larger contribution to GSL rise from other (natural and anthropogenic) causes than otherwise required.There are some obvious places to put a whole lot of water, for example moving water from the soaked east coast of the US to the west, or simply using it to recharge the Ogallala Aquifer. In Africa, pumping water from the Med to fill the Qattara Depression, and in Asia, refilling the Sea of Aral.
Not that these ideas have gone unmentioned in the past, but, of course the issue is where to get the energy needed to move the water. Eli has half an answer. Solar and wind power, as has also been not unmentioned, suffers from intermittency. To handle this intermittency requires overbuilt capacity, geographically spread out. When there is excess electrical power, that excess can be used to move water into storage reservoirs, both above and below ground. With proper design, some storage schemes (as Arthur points out) can be used for hydro generation of electricity when needed.