I just learned that some people in Vancouver Canada are on water rationing. They can only water their yards every other day. Maybe the Canadian government is doing that because they want to sell the water to people who need to refill the aquifers?
OTOH, a recent story about the drought causing some people’s wells to dry up talked about some businesses that would come out and flush water back down into your well so you could draw it back up over the next week. One guy was selling 2100 gallons per week to some people for this purpose. Made me wonder why the hell they didn’t just rent out or buy big waterstorage tanks.
Here in South Oz, one of the local councils pumps storm water into an aquifer. However this is less a simple act of restoration, rather they are using the aquifer as a very large filter and store. They withdraw roughly what they add. However their ability to use otherwise unusable storm water means they save a lot of water form other sources. We have serious water issues down this part of the planet.
Long term I do wonder if they could be considered to be depleting the aquifer’s ability to hold pollutants and sediment - eventually clogging it up. Thus deleting another natural resource. Nothing is easy.
Water is sometimes added directly to aquifers through injection wells, but usually only for a few specialized applications. If they’re not drilled into a water supply aquifer, they can be used as disposal sites for treated wastewater, stormwater runoff, or other relatively benign waste streams, and wells that are particularly well isolated from water supplies can be used as disposal sites for hazardous wastes. They’re used for on-site remediation of groundwater pollution in a pump and treat system (just what it sounds like: contaminated water is pumped out of the aquifer and treated; the treated water is then reinjected). As Francis Vaughan says, they’re also used as short-term storage for future use. In the Middle East, I think they’re used for groundwater recharge, but I’m not aware of any injection wells for this purpose in the US. If you’re curious, you can find details on the EPA’s injection well regulations regulations here.
Yes and no - remember that sedimentary deposits tend to be layered, with different properties depending on what kind of material you have and how it was deposited. Their ability to hold and transmit water varies layer-by-layer as well, so you have different kinds of aquifers. Percolation ponds will allow water to flow into unconfined aquifers (see the illustration here), but that may not be the same aquifer that local wells are tapping. It’s more common to discharge to an area that’s not hydraulically connected to your water supply just to minimize the risk of contamination if something goes wrong.
Groundwater doesn’t typically require the same level of treatment that surface water does - it’s less likely to contain particulates or bacterial contamination. However, it’s more likely to contain higher concentrations of dissolved solids (calcium and sodium salts, metals, sulfur, etc.), so it’s not an either-or proposition.
Pumping river water directly into an aquifer (close to a supply well) would give you the worst of both worlds, and strikes me as a Very Bad Idea.
The other problem is hat in many of these aquifers, the water percolates slowly through porous rock. You can’t just add half a river’s flow and have it fill the rock layer like it was an empty tank. If the water is not addednear where it was taken out, there could be decades or longer for the water to go from the more wet area where recharge happens, to the area where it is most exploited.
OTOH, the “porous rock” is a natural filter for a lot of the non-soluble contaminants - silt, bacteria, etc. The downside is that fine silt will eventually plug your input hole, slowing the rate at which water percolates inward. You can’t replace thousands of square miles and thousands of years of slow seepage with a pond and some drill holes, especially when some farmers are probably pumping as much onto one farm as you are trying to put back in for the whole aquifer.