Wednesday, November 18, 2015

Shallow is good

Last summer I took the World Bank MOOC course on climate change in Spanish (it will be offered again next year in both English and Spanish). My final presentation was on using shallow aquifers to mitigate and adapt for climate change.

Many communities located near coastal areas or on large floodplains have multiple layers of aquifers separated by clay layers. The shallowest aquifer is usually not used because of contamination risks, but it has a lot of advantages in terms of receiving recharge and requiring less energy to use, as long as you don't drink it. Australia figured this out, and a lot of other places should do the same.

Last week I finally translated and updated the presentation, including a PowerPoint on an urban shallow well/recharge system in Redwood City near Silicon Valley. For anyone interested, the English version is here, and the Spanish version here.


Fernando Leanme said...

I have a house in the USA with a very shallow aquifer system. The water coming off the washer goes down a pipe which distributes it under the backyard lawn. The water we use to water the lawn comes from a very shallow well located in the backyard. From what I can tell the washer water fertilizes the hell out of the soil (we are getting huge fruit from the trees), and the water from the well seems to be fine.

Russell Seitz said...

I'm greatly impressed by Rajendra Singh's low dam water slowing for aquifer recharge work in Rajastan.

Are similar projects contemplated in California or on the east flank of the Sierra?

Aaron said...

Concept should be expanded for the Ca Central Valley.

And,the problems related to recharging the Fountain Formation under the western plains (from Ne to Tx) should be considered in the context of the cost of depletion.

Today, many of our surface waters are cleaner than they were when the rules against aquifer recharge were developed. And, today, we have better filter system technology. And, we have more high capacity irrigation wells to act as down flow channels.

The success of RCRA, CERCLA, CWA, and CAA give me some hope that AGW can be controlled.

Brian said...

Fernando - that's really interesting. Do you know your well depth? And what part of the country is this?

Russell - many years ago I saw a similar thing in Maharashtra. Don't know about eastern Sierra, but there's a proposal being considered to spread floodwaters on irrigated fields in Central Valley to promote infiltration. I think that's good flood irrigation, versus bad flood irrigation that's just a misuse of water to irrigate crops.

Aaron - I don't know Central Valley as well, but I think perched aquifers aren't as extensive there. Maybe some places near rivers and lakes. And I agree the water is cleaner than it used to be - shallow water might be drinkable, but that's not the way I'd promote the idea at this point.

Russell Seitz said...

Singh's foundation works all over northern India- the point is that you don't always have to build water tight dams , just structures that slow downhill flow .

Increasing the percolation time from minutes to hours in this way has recharged tens of thousands of wells and saved over a thousand villages from abandonment dur to falling water tables.

Howard said...

Soundbytes like shallow is good is ignorant. What is the baseflow impact? Fernando is talking about gray-water recycling and you are too ignorant of real-water to recognize he is solving the problem in the correct manner while increasing baseflow. Aren't you the Einstein who wants everyone to have their own reservoir under their house with their own treatment system, monitoring program, maintenance program and capital improvement program? You were one of those board members who thinks operations happens by magic.

Aaron said...

Pour water down an irrigation well in the weather and pump it back up in the summer. Even if the water is not fully drinking water quality, the summer water retrieval will keep it from migrating going too far, so this is not like a disposal injection well scenario.

The flood water will likely carry a fair amount of silt, and many pollutants will partition on to the silt, and the silt will be rapidly filtered out as the water percolates through the formation. Thus, one issue is clogging the aquifer. That is an issue depending on silt levels in the flood water (after flowing for miles through a irrigation canal, where much of the sediment and attached pollutants will drop out) at the and the nature of the formation.

I agree, that is would likely be best to use old wells so the water is injected well above the current ground water levels.

I think this group should argue for concepts that will keep piles of grad students fully employed for almost as long as it takes to get full set of permits for a new surface dam. (Read as a long, long time!)