The Umatilla Basin in Eastern Oregon became Oregon's bread basket through irrigation based on pumping water from deep aquifers. A report in the Oregonian says that groundwater is being depleted much faster than can be replenished by the 12-13 inches of annual rain in the area, and water levels have dropped 500 feet in some of the basin's aquifers. One dramatic measure of how this natural capital is being depleted: Carbon-14 dating has shown that some of the water being pumped out has been underground (and thus not exposed to the atmosphere) for 27,250 years!
According to the Oregonian, a proposal in the works would reverse this by diverting some 32 billion gallons of water from the Columbia River during the winter months, filtering it by percolation through a shallow alluvial aquifer, and then injecting it into deep basalt aquifers through existing wells. In the summer, the water would be pumped back out for irrigation. This saves the heavy river flow in the winter for the critical summer months without needing expensive above-ground reservoirs, and also allows the river flow in the summer to be used for other purposes (electricity generation, salmon/steelhead migrations). The most encouraging part is that it largely relies on the existing infrastructure of irrigation pipes, pumps and wells. Sounds like an absolute win-win if there are no engineering problems with the plan.
Large-scale recharging of aquifers -- from both river water and rain water -- is of significant interest for a couple of reasons. In places like Oregon, one of the effects of climate change is going to be increased winter rain, reduced snow packs, and earlier melting of snow packs -- resulting in increased winter river flows and reduced summer flows. The mountain snow packs have historically been a water storage mechanism, storing winter precipitation and then converting it to summer water supply, but nature is starting to cut back on this free 'service'. Artificial storage in aquifers could help maintain a more balanced water supply throughout the year. Elsewhere, in developing countries where groundwater is being depleted rapidly for food production and industrial uses (see for example, this and this), reliable methods of recharging aquifers could contribute to economic and food security.