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Tapped Out: How Will Cities Secure Their Water Future?

Water depletion tapped out map
Half of all cities with populations >100,000 are located in water basins in which more than half of available water supplies are being depleted during some portion of the year.

Today, global demands for food, energy, and shelter are putting unprecedented pressure on the resources of the planet. Water is at the heart of this crisis.

In fact, more than half of the world’s cities are already experiencing water shortages on a recurring basis – based on findings from a study that I published, along with 13 of my colleagues, this week in the Water Policy journal. These water-stressed cities are finding it extremely difficult and expensive to secure the additional water supplies needed to support their growth.

Our study, “Tapped Out: How Can Cities Secure Their Water Future?” highlights the reality that many growing cities are badly in need of new, low-cost, and reliable sources of water. We found that a key strategy cities should consider is to form partnerships with agricultural producers to conserve water use on farms, thereby freeing up water that can be used in the city.

Even a modest level of reduction (15-20 percent) in agricultural water consumption, globally, could make more water available than all the water consumed in cities and industries today.

Where Did all the Water Go?

In conducting the study, we identified cities around the world that are situated in water-scarce regions, and then assessed how water is being used in those regions.

It was not difficult to see why so many cities got into trouble with water.

The water sources they depend upon – rivers, lakes, and aquifers – have for decades been heavily used for irrigated agriculture.  Since 1950, the consumption of water globally for irrigation has tripled in volume, a trend that played a large role in enabling food production to more than double over the same period.

The result:  Water-stressed cities are trying to expand in places where most of the water is already being consumed by irrigated agriculture. In fact, more than 90% of the water being consumed from those shared water sources is going to growing crops.

In particular, we closely examined the challenges and responses of four cities: Adelaide, located just outside but dependent upon the Murray–Darling River Basin of Australia; and three cities in the U.S.: Phoenix, located in the Gila River Basin in Arizona; San Antonio, dependent on the Edwards Aquifer in Texas; and San Diego, which relies upon the San Diego, Colorado, and Sacramento River Basins in California.

The Unsustainable Pursuit of More Water

Looking at the investments that these cities have made – and plan to make in the future – to access more water, we found similar patterns in their water development: 1) They began by exhausting their local surface and groundwater supplies; then 2) imported water from other rivers and aquifers; and finally 3) turned to recycling of wastewater or stormwater, or desalination of either seawater or brackish groundwater.  We found that water conservation efforts did help mitigate, to varying degrees, the timing of water-system expansions and the extent to which cities had to rely on new sources of supply.

Fig. 10 - Phoenix Supply Color - no title
Trends in water supply sources for the Phoenix metro area.

We found this typical water development pattern to pose significant problems from a sustainability perspective – as it is usually associated with serious negative ecological and social impacts – and lacking cost effectiveness.

The heavy exploitation of freshwater sources – a result of growing urban demands on top of heavy agricultural use – has caused severe damage to freshwater ecosystems, impaired the ability of ecosystems to provide services to people, and created health problems in many regions. In addition, groundwater depletion (lowering of underground water levels) has led to increased electricity costs for pumping the water from ever-increasing depths.  When cities extend their reach into other rivers or aquifers to access water supplies, they spread negative impacts over great distances. Energy-intensive technologies such as recycling and desalination are expensive, resulting in higher water bills for consumers as well as increased carbon emissions that accelerate climate change.

Fig. 9 - Colorado River Decline - no title
Water flows in the lower Colorado River have been heavily depleted by agricultural irrigation and urban water consumption, resulting in considerable damage to the river ecosystem and its species. This has in turn led to severe impacts on indigenous cultures dependent on fish and other resources in the delta.

So, what can be done?

Place Your Bets on Water Conservation

Far and away, water conservation is the most cost-effective, immediate, and environmentally desirable means for addressing water shortages.  But few cities have maximized their conservation potential.

Fig. 18 - San Diego Future Costs - no title
This comparison of the costs of future water supply options for San Diego illustrates the impressive cost-effectiveness of both urban and agricultural water conservation.

In addition to investing in urban water conservation – e.g., by installing low-water plumbing fixtures, fixing leaks in water distribution lines, or reducing landscape watering – considerable potential exists to make more water available locally by reducing water consumption in irrigated agriculture.

Promising opportunities exist to free up the water presently used in agriculture through techniques such as reducing unproductive water consumption (e.g., stopping canal leakage, reducing soil and reservoir evaporation), changing crop types, introducing rotational fallowing, temporary fallowing during droughts, or the elimination of low-value farming.

In our recommendations for water sharing going forward, we advocate for ‘urban–rural partnerships.’ While there are formidable hurdles to forming urban–rural partnerships to share water (these challenges are detailed in our paper), the payoff is too big to ignore.

In many basins, a reduction of agricultural water consumption of just 15–20% can yield massive volumes of water that can be saved for other uses. For example, if adopted globally, this level of reduction in agricultural water consumption would make more water available than all the water consumed in cities and industries today.

A Role for Markets?

Our paper also highlights the role of water markets in facilitating water sharing and transfers of water rights among cities, farmers, and environmental interests.  For example, my organization, The Nature Conservancy, is exploring how to expand water markets more broadly. In places where water markets exist, such as the Murray-Darling Basin in Australia or in the Edwards Aquifer of Texas, we see the potential for multi-win benefits to farmers, cities, and the environment. Just as a farmer can sell “saved” water to other farmers, or cities, we can serve as the buyer or help facilitate the purchasing of a water right, and allow the water to remain in the river or aquifer to support ecological health and water availability for other uses.

In addition to the Murray-Darling and Edwards Aquifer, we are looking at opportunities to buy water for conservation purposes in the Guadalupe River in Texas, the Colorado River Delta, and other places.  We are also working with local governments and water users in the U.S. and abroad to create new water markets, or to improve the functioning of existing markets, so that water is available to those that need it most.

But perhaps most important of all, we are also working with governments to help them understand the hazards of overusing a water source.  When too much water is being taken from a river, lake or aquifer, everyone is at risk!


  1. Blake
    United States
    October 14, 2016, 12:59 am

    Is this peer reviewed ?

    • Brian Richter
      October 14, 2016, 6:09 am

      Yes, through the peer-review process managed by the Water Policy journal, in which the paper was published.

    October 9, 2013, 3:04 pm

    Peoples are not worry too much. peoples are in a financial turmoil and not realizing the water shortage. as long they can pay the price of the water- They go for it. These statistics and figures are frightening. They are hidding the risk drivers-So, peoples may never get up to know how to make to change their behaviors toward the water element. particularly, if government are no strong enough- The water risk will make the job,…Some cities are already with water cuts (India…increase of water pollutions every where. how it has come that our daily needs (water biological need is 2 liters per day. But, our water economical need is mmuch much higher….). How do we move from there with increase cost of water….?

  3. Gerry Cash
    September 12, 2013, 8:30 am

    Considering that technologies exist (including our own new RainSafe) that will treat Harvested Rain Water to potable standards, I question if the benefits of RWH should not be extolled to a greater extent. Harvesting Rain Water at source (in home owners gardens) particularly in areas affected by extreme weather conditions – monsoon followed by drought – where the water can be treated and used for drinking later would alleviate flood problems and lessen water wastage where rainwater runs away (all too often ending up at sea0.

    • Brian Richter
      September 17, 2013, 7:42 pm

      Gerry, I fully agree that rain water harvesting should be implemented to a much-greater level. It will be quite beneficial to individual homeowners or businesses that need to irrigate landscaped areas or gardens, for example. But in terms of rebalancing overdrawn water budgets in most of the world’s watersheds and aquifers, we’re going to need to do a lot more than capturing local rainwater or runoff. See my comment below for further elaboration.

  4. Pat Browne
    Ventura County, CA
    May 16, 2013, 10:38 pm

    Nice overview. I am still finding a lack of focus on the whole picture of the water cycle with lower to no attention placed on Storm water capture and rain harvesting units at the decentralized level. As much as the electric grid will be impacted by panels going up on every roof, so will the water recharge need to look at every home/business tanking the runoff from the property. Especially now with our rivers becoming increasingly “flashier” and flooding from larger deluge, we have to keep looking at slow/stop/dropping the water we do get. Remember think Global, act local and include the little guy with urban planning.

    • Brian Richter
      May 17, 2013, 9:42 am

      Pat, I like your enthusiasm for decentralization and ameliorating the undesirable impacts of excessive storm water runoff on our streams. I have a 600-gallon rainwater tank installed in my own backyard, which we use to water our vegetable and flower gardens. But our Tapped Out paper addresses the challenge of meeting the water supply needs of entire cities and farms in the 21st century. The use of rainwater or storm water capture alone will not be sufficient to meet this challenge. To begin with, you cannot (or at least should not) drink rainwater without proper treatment. That’s one challenge to overcome. But then, even if you could treat that water in a decentralized manner, most households will still not be able to capture and treat a sufficient volume of water to meet a family’s needs. My 600-gallon tank, for example, would provide enough for one family of four for only one day, and it doesn’t rain every day where I live. In addition to a family’s direct needs for water, we also need to address the water needed to produce our electricity, and the water required to grow our food or to grow the cotton that goes into our clothes. Our paper suggests that the best place to look for more water is in agricultural water conservation. We estimate that a savings of just 15-20% in irrigated agriculture would resolve much of the water shortage facing our global population.

  5. Naheed Iqbal
    United States
    May 10, 2013, 10:58 pm

    Very informative article (and nice poem Ima!) i am curious about water markets—does the price of water in these markets depend on sensitivity of the water resource, how badly the buyer wants to buy it and for what purpose, the quality of water?? is there any agency overseeing this ‘trade’ in water- also what about virtual water- does that get included in water imports or exports- also the cost comparison for various alternatives— what timeframe are we considering- is it possible that some options such as recycling are cheaper over longer term? i am guessing you have covered that in the paper so ill try to read that—But yes interesting article and i loved the pie charts!

    • Brian Richter
      May 11, 2013, 11:53 am

      Hello Naheed, thanks for the supportive comments. Our Tapped Out paper doesn’t discuss water markets in much detail, other than to suggest that opportunities for water sharing between farmers and cities needs to be better facilitated. We are now writing a paper on water markets that will address your questions more directly, but in the meantime I can tell you that yes, in a market setting the price of the water can increase with scarcity, and the specific needs of water users in the area. What we have seen in the Australian market, particularly in the Murray-Darling River basin, is that water trading is proving to be a very effective means for farmers to meet their irrigation needs in dry times — some farmers will look to buy water, and other farmers will decide that they can do better by selling or leasing their water to other farmers. We are also seeing that the presence of a market can be a strong incentive for conservation, when the market is functioning properly. Lastly, markets create opportunities to provide better protection to freshwater ecosystems, because they enable governments or environmental interests like my organization (The Nature Conservancy) to purchase water rights for ecological purposes.

  6. Blanca Surgeon
    Santa Fe, NM
    May 9, 2013, 12:51 pm

    Thank you very much for the article. Thank you for showing the benefits of water conservation. I have been an advocate of water conservation stating that it should be a national campaign. When I was a member of the National Drinking Water Advisory Council to the EPA we discussed this issue and continue to do so. But there is no funding to develop and maintain a national campaign. When I ask why we don’t put a better effort into conservation, the answer has always been, we don’t want to create a public panic that there is no water. We need to get away from that mentality. Water conservation can be put at the forefront without creating a panic. But economic development is more important and everyone things that if they make their water scarcity public they won’t get companies moving in. Please do a study on that. Thank you. Blanca.

    • Brian Richter
      May 9, 2013, 7:08 pm

      Thank you, Blanca, for that very enlightening comment about why some cities don’t want to invest in water conservation: “everyone thinks that if they make their water scarcity public they won’t get companies moving in.” I honestly had not understood that point previously, but it helps explain some of the recalcitrance to invest adequately in conservation even when it is clearly the most economically-responsible way to meet urban demands!

  7. David M Newlin
    May 9, 2013, 12:29 pm

    Dear Ima;

    First, provide a solution with your whining. Second, government solutions are better or worse than private industry? BP comes to mind. Third, stop making smart aleck comments behind a pseudonym. Nothing helpful in your post AT ALL.

  8. Ima Ryma
    May 9, 2013, 1:42 am

    The urban versus rural fight
    Over water will just get worse.
    Deciding on who’s got the right,
    Depends on the size of the purse.
    Big gov wants to get bigger, so
    Those who can “bribe” big gov the most
    Will get first dibs on water flow.
    That problem solved, big gov will boast.
    The haves will have fresh water to
    Do with and waste as much as bought.
    What will the have nots have to do?
    Gripe about their waterless lot.

    In the end, big government will
    Decide which ways the waters spill.