Sustainability of Irrigated Agriculture

Some notes from a talk this morning by Dr. Bridget Scanlon, delivered in a lovely Irish lilt occasionally disrupted by vaguely disturbing Texanisms like “folks”.

– despite the local nature of groundwater work, top journals don;t like local results. You can get much further doing similar studies in iddferent regions.

– For the first time, the LCRA (our local water authority) has cut off supplies to rice farmers.

– Money can buy water. More specifically, money can buy energy, and energy can buy water. But then there are energy constraints…

– Irrigation amounts to 70 % of fresh water use (in US?) . 40% of freshwater supplies are mined.

– Irrigated lands are 30% of cropland but produce 70% of crops by value.

– depletion occurs maximally toward the equatorward edge of an aquifer. Nebraska is not being drawn down, Kansas has over two centuries left, Texas half that, some localities much less. (I was surprised that the time frame is that long, to be honest.) Ogalalla is 8% depleted.

– ground water and surface water in many places are parts of the same system and it doesn’t matter which one is withdrawn. Australians in particular are confused about this in management of the Murray-Darling system, their main agricultural zone.

– significant water withdrawals directly or indirectly from surface waters impact endangered species, ecosystems

– GRACE data is verified by local measurements in US aquifers; resolution is adequate for Ogallala, marginal for California central valley

– in parts of California so much water has been withdrawn that there has been as much as 10 meters of subsidence of the surface

– more efficient drip systems can help

– groundwater withdrawal is a term in sea level rise

The most interesting point in my opinion was a generalization that Dr Scanlon made: “As a general rule sustainability trades off against reliability.” She even made a schematic graph, which I thought was taking it a bit far. But the point is worth considering.

map – USGS via


  1. (Background) Beside nuclear power, one of the largest issue in Japanese politics is whether this country should join TPP (Trans-Pacific Strategic Economic Partnership Agreement). Even though TPP was initiated by Singapore, Brunei, Chile and New Zealand, Japanese journalists usually equates joining TPP with following what the USA (perhaps the pro-free-market end among US policymakers) tells in international trade policy. It is told as if it is inevitable, perhaps because part of the Japanese land is still occupied by the US armed force purportedly due to request by the Japanese people. (Actually the public mood is ambivalent; the current situation may be better than having a influential home-grown military sector.) And it is told that, if Japan accepts the principle of TPP, it must abolish all tariffs. It is somewhat interesting that the issue of TPP makes a schism among the right wing (market fundamentalists plus pro-US people on one hand, and chauvinists on the other hand). If there is real policy issue, it is agriculture. Food price in Japan is high primary because the average income of Japanese people is high. If Japanese farmers must compete imports without tariffs, and also government subsidy is considered evil, Japanese agriculture may perish.

    (Opinion) I think we should change the notion of free trade, whether the TPP or bilateral free trade agreemnets or the global WTO regime, to match the notion of sustainability. Fair comparison of price must include evaluation of all externalities (in academic economists' term). If a country exports agricultural products produced by reducing the natural capital (in Daly's sense), I think that the importing country may judge it as dumping and charge a tariff amounting to the external cost not paid in the exporting country. Actually it is difficult to evaluate the external cost. The targets of charging should be extended gradually. And the first phase can include consumption of fossil groundwater and consumption of fossil fuel in production of food and animal feed.

    How do you think about this idea?

  2. I've had similar thoughts. Or even better, engineering a direct solar solution, just the way sea salt is made, except capturing the water rather than the salt.

    The enormous King Family ranch (essentially coterminous with Kenedy County) is the ideal location, though I wonder if they'll want anything to do with something like that. I think it's fair to presume that Texas royalty doesn't skew environmentalist.

    It remains a fact that Texas could be as much a leader in 21st century energy as it has been in the 20th. Some folks have noticed. But on the whole, the Texas establishment is being oddly blind to where (and whether) its bread might end up being buttered.

    Even so, to some extent Texas is in the lead in wind and solar deployment, ironically because of, rather than despite, limited regulatory constraints.

  3. There is plenty of expertise in groundwater development at my institution. The focus is regional and operational.

    Peter Gleick may be an expert at the global scale, and that is certainly important. I would be the last to say otherwise. But the global scale is mostly the aggregation of very weakly coupled local issues - the main coupling being through food prices.

    As I become used to living in a semi-arid, drought-prone area with many competing water uses, I find that my past vague intuitions about how this might work do not serve well.

  4. Peter is a leading expert on California water issues, albeit not irreplaceable. I do expect he won't need to be replaced in that role, though. If that did happen it would be a considerable loss, though.

  5. David, the point is that as reliability increases it requires things to be done that are less and less sustainable. When speaking in terms of sustainability, obviously she's not referring to anything resembling the current agricultural economy (which has been made to be relatively reliable).

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