Through the course of the semester and the first 9 modules of the class, you’ve learned about the science of water – including the distribution of fresh water; the demand for water and its relationship to geography, uses, population growth, and climate; and the physical principles that govern surface water and groundwater replenishment and movement. You’ve also considered some of the historical, political, ethical, and economic issues with water allocation and management, for example by considering the impacts of dams, or the annexation of water rights to support cities in arid regions.
In Module 10, the culmination of the course, you will explore potential solutions to the problems of water quantity and quality, especially in the face of population growth, increasing energy and food demands, and greater awareness of (and sensitivity to) the environmental impacts of water development. As major population centers, many of which are not ideally located with respect to water resources, continue to grow, we are faced with serious questions about sustainability: How can water supply and quality be assured, and balanced between the demands of irrigation and cities? Is there a technological panacea, or is a mixed portfolio of approaches required? Is it possible to hedge against climate change and predicted shifts in the timing and spatial distribution of precipitation? How can cost be managed, while minimizing the impact on the environment? Can diverse cultural and political entities work together to implement solutions, or deal with side effects, that cross state, and national boundaries?
By the end of this lesson, you should be able to:
In The Big Thirst, Charles Fishman repeatedly notes that while water problems are universal, they are fundamentally local and not global problems, in the sense that the issues are specific to a particular area, and excepting major water transfers, can most effectively be solved locally or regionally. Put another way, if you think back to Module 1, you’ll recall that if it were evenly distributed in time and space, the total precipitation that falls on Earth as part of the hydrologic cycle would be sufficient for water supply and dry land farming. The problem is not that there is not enough (or clean enough) water on the planet; it’s that the water does not fall when and where we need it. The fact that there is enough water globally does not help us all that much, because it is simply too expensive, impractical, and energy-intensive to move large volumes of water across oceans or between continents – though recent developments may challenge this mindset. Furthermore, the problems that face different areas are different: in Delhi, the major problems are related to water quality and infrastructure (i.e. Chapter 8 in The Big Thirst); in Las Vegas and Los Angeles, the problems are related to water scarcity and supply (Chapter 3); and in the Murray Basin or Perth, Australia, the problems are related to major shifts in supply and allocation in the face of changing climate (Chapter 7). Therefore, viable solutions are by nature local or regional – to obtain, manage, or treat water for a particular need and place. Potential Solutions to Problems with Water Scarcity and Quality
Here, we will briefly describe some of the most promising solutions on the horizon, many of which have been implemented as trials or in specific regions where the balance between demand and cost have made them feasible. We will also draw heavily upon readings from the textbook that you’ve completed for previous modules. For the assignment and activity linked to the module, we will ask you to develop a “portfolio” to secure future water supply for one of the population centers we’ve discussed in class (e.g., Las Vegas, Dubai, Los Angeles, etc…). This will require that you integrate much of what you’ve learned over the semester about precipitation patterns, surface water, and groundwater systems, water quality, water management and demand, cost, and infrastructure.
As you may remember from Module 1, the majority of Earth’s accessible water (i.e. not including a large amount of water trapped in minerals in the Earth’s interior!) is in the Oceans. In a sense, the Oceans would provide an unlimited supply of water, but of course, they are too salty to drink or use for most purposes. To use seawater for industrial, agricultural, or domestic/municipal supply, therefore, requires the separation of the water from the dissolved ions (mainly Na, Cl, Mg, SO4, Ca, and CO3). This can be accomplished in a variety of ways, but most commonly is done via either:
Of these, reverse osmosis (or seawater reverse osmosis, SWRO) has emerged as the more efficient approach, especially when scaled to produce the millions of gallons per day or more needed to meet the demands of even modest population centers.
Of course, removing the salt from seawater requires energy – and money. For that reason, it has been a subject of intense research and engineering efforts, in order to reduce costs through increased scale, improved efficiency, pre-filtration, and improved materials (most importantly, advances in membrane materials that require less pressure to push the water through but still exclude dissolved ions). Early desalination plants were restricted to a relatively small scale, and mainly in desert areas (e.g., the Middle East), or to meet water quality requirements for the CO river treaty of 1944 (e.g., the Yuma desalination plant in Yuma, AZ, brought online in 1997). However, with improving efficiency, increasing demand, and perhaps spurred by drought, desalination is now emerging as one potential viable solution, at least in areas with access to the ocean, and the economic resources to construct and operate the plants.
Technological advances, coupled with innovative approaches to reduce energy costs (i.e. by using solar, tidal, or ocean thermal energy) have helped to make SWRO a potential solution to water supply or hedge against climate change for large cities like Perth - rather than simply a novelty for wealthy countries. In the 1970s, SWRO costs hovered around $2.50/m3. Currently, costs for the most efficient plants are well below $1/m3, or between ~$1000-2000 per acre-foot (Figures 3 and 4). This is still more expensive than imported surface water or groundwater in most areas (these costs range from $400-1000/acre-foot, depending on location), but in the realm of viability for areas without those sources, or to augment limited supply. The total costs include everything from construction costs for the facility (amortized over its expected lifespan), land access, permitting for discharge and intakes, and operation & maintenance.
Despite its promise, it remains to be seen if SWRO will be a universal or large scale answer to water scarcity. In particular, key challenges include the (still relatively high) costs and associated energy demand; management of the environmental impact associated with intakes and disposal of the brine waste stream; delivery of SWRO water to regions away from the coast; and the up-scaling that would be necessary to meet demand for irrigation or industrial use.
Current water rates (cost for the consumer) in Las Vegas are $1.16 per 1000 gallons. From the data shown in Figure 6, calculate the typical cost of SWRO per 1000 gallons for 2010. Do the same for 1982. How much higher are SWRO costs than current water rates in Las Vegas for the two cases (i.e. are they double the cost? Triple? Ten times?). (Hint: You’ll need to convert between m3 and gallons: one m3 is equivalent to 264 gallons.)
1982: $1.55/m3 x 1m3/264 gallons = $0.0059/gallon x 1000 gallons = $5.90/1000gal. This is about 5 times the cost of typical water delivery in Las Vegas.
2010: $0.93/m3 x 1m3/264 gallons = $0.0035/gallon x 1000 gallons = $3.50/1000gal. This is about 3 times the cost of typical water delivery.
As we’ve already seen in Module 8, one increasingly viable strategy to address limited water supply is that of treatment and re-use. This can take a variety of forms, including reclamation and re-use of wastewater for industrial or consumptive applications like golf courses or parks, or treatment of wastewater to meet drinking water standards and re-use for domestic/municipal supply. The former constitutes a major element of Las Vegas’s approach to maximizing their limited allocation of CO river water from Lake Mead. The latter is becoming increasingly – though not universally - accepted as a way to increase supply, and has been implemented in several areas, including Orange County and even at Penn State!
The Orange County Groundwater Replenishment System (GWRS) is one well-known case study of wastewater reclamation for municipal supply at a relatively large scale (Figures 5-7). The GWRS plant is a 70 million gallons/day facility (72,000 acre-feet/yr) and generates enough potable water for ~500,000 people. The facility also solves the secondary problem of managing effluent to the ocean because much of the wastewater that would otherwise be discharged offshore is captured and re-used. The facility takes advantage of proximity to the wastewater treatment facility to allow for low-cost and efficient “on-site” treatment and uses gravitational energy to transfer the water for treatment. The cost of the facility was subsidized by grants. With the subsidy, the cost of treated water is ~$400-500/acre-foot; even without the subsidy, the cost is competitive with imported (CO River) water at ~$800/acre-foot.
Two key advantages to reclamation and re-use are: (1) the supply is by definition local, in that it was used by the same people who would use it again, and has already been captured for treatment. This substantially reduces the need for infrastructure and conveyance, and thus is highly efficient and reduces cost; and (2) the total dissolved solids (TDS) in wastewater are much lower than in seawater, such that the energy and cost are low in comparison to SWRO (Figure 8).
Another more local example is that of the Penn State “Living Filter”, which has been in operation since the early 1960s, and in full-scale operation since the mid-1980s. The treatment facility captures approximately 2.5 million gallons per day (the total water use on campus at the University, plus a small proportion of water used by residents of the nearby Borough of State College). This water is originally sourced from a fractured limestone aquifer that underlies the region. Rather than treating the wastewater and discharging it to local surface waters (Spring Creek), the water undergoes primary and secondary treatment, followed be de-nitrification and minimal chlorination to ensure that any (unlikely) remaining pathogens in the water are killed, and then spray application in the aquifer recharge area. After treatment, the biological oxygen demand has been reduced by 95-99%. The term “living filter” refers to the thick (>50-75 foot) soil column that overlies the aquifer; the combination of physical processes in the soil, natural degradation by exposure to soil acids and UV, and microbial activity effectively “filter” the treated wastewater to meet drinking water standards. In total, the system is almost 100% efficient in the re-use of extracted groundwater, with ~1 billion gallons of treated water per year recharged to the aquifer.
Of course, there are some obvious drawbacks to water re-use, though these are arguably mostly psychological and rooted in the so-called “Yuck Factor”. It is easy to forget that water is the ultimately reused product. The water in our rivers and oceans has certainly cycled through many organisms over the course of its history (think “dinosaur pee!”). The surface water that we think of as “clean” and which has historically been the dominant water supply for human consumption, hospitals, laundry, and other uses, is mixed with discharged treated wastewater from upstream communities. For that reason, we treat surface water before use. In this sense, why or how is directly treated wastewater any different? Likewise, rural domestic wells are often down-gradient of septic systems or leach fields, albeit a safe distance to allow natural degradation and filtration in the soils and aquifer system. Fundamentally, this raises the question of whether we would rather drink and do our laundry with water that was once our own wastewater, or somebody else’s.
As we covered in Module 8, one additional hedge against fluctuation in supply, and/or against climate change, is to purchase, trade, or bank water, either using one’s own allocated water in times of surplus or through the purchase of someone else’s unused water rights in a given time period. For example, Las Vegas has adopted this strategy to provide alternate sources in times of severe water shortage, through agreements with Arizona and California. These agreements are one means to transfer water, either actually or virtually, from areas where it is available (in surplus or actively stored in aquifers) to those where it is needed.
More sophisticated arrangements have also been explored, in which water is treated as a commodity and with prices determined by demand. One example of this is described in the High Country News piece “LA Bets on The Farm” [8]. The basic concept is that the MWD of Los Angeles pays farmers with water rights for irrigation to fallow some portion of their land. Because, at least currently, there is no shortage of food, the exchange works: LA gains an additional water supply, and the farmers or irrigation districts make a bit of money (without having to take on any risk associated with growing crops, commodity prices, or the like). A more recent iteration of the agreement provides both parties with additional flexibility to account for unpredictable precipitation patterns and water supply, whereby the MWD purchases “options” to the water rights for $10/acre-foot. By March of that particular year, the MWD must decide whether they will take the water or not. If they do, they pay an additional $90/acre-foot (enough that the irrigation districts make some money); if not, there’s still time to plant crops, and the irrigation district keeps the option fee.
At their core, these approaches use the market to define the pricing of water and to shape the terms of agreements that will be mutually beneficial. In part, they work because the amount of water needed for irrigation far exceeds that for municipal or domestic uses (see Module 1). And in part, they work because the irrigation districts receive water that has been heavily subsidized, largely through public investment in major infrastructure that underlies the water systems. Ultimately, however, it is not clear that the exchange or purchase of water rights will really work in the face of severe drought, major climate changes, or continued increases in demand. After all, these strategies are essentially a form of regional water re-allocation or transfer – but in a zero-sum game, they can only work if there is enough surface water or groundwater to be had.
Recognition that these strategies may ameliorate shortages and can serve as a valuable hedge against variability in supply, but are unlikely to fully solve problems of water scarcity if we insist on continued development in water-poor regions, has led to large-scale proposals to transfer water or exchange water rights over great distances and across borders. For example, as discussed briefly in Module 8.1, and in Chapter 3 of The Big Thirst, Las Vegas has begun to explore distant sources of water. These include groundwater in Central and Northern Nevada (a project currently underway), as well as proposed exchanges in which Las Vegas would bankroll desalination facilities in Coastal California, and trade the “new” supply of desalinated water for withdrawal of the same amount from Lake Mead. As described in the next section, the basic fact that there is water available if one reaches far enough – and is willing to pay for it - has led to all manner of proposals to move water across oceans and continents. To an extent, this calls into question Fishman’s assertion that all water problems and their solutions are “local”.
Explain (~100 words) why water banking or optioning is not a viable long-term solution to water scarcity in the case of prolonged water shortage related to sustained severe drought or climate change.
Answer/talking points: Should note that these approaches are no more than water trades, either with other end-users at the current time, or for future water access or rights. These strategies, therefore redistribute or reallocate water to meet the greatest or most severe demand. But if there is simply not enough water to meet demand on a long-term basis, reallocation cannot solve the problem.
If you have ever carried your water on a camping or backpacking trip, you know first hand that water is heavy, and therefore that transport is costly and energy-intensive (that’s why there is a market for water filters and iodine tablets!). For example, almost 20% of electricity in California is used for the water-related activity, and much of that to move water across the state. Despite the high energy and economic cost to transfer large volumes of water, it remains the only – and ultimate – hedge against uncertain supply. As you’ve heard from Marc Reisner and George Miller in the Cadillac Desert films we’ve watched, the idea behind many ambitious water proposed water projects in the Western US, many of which never reached fruition, was to “go where there was so much water, you’d never run out”, and construct “pipelines beyond the wildest imagination”. Patricia Mulroy has even suggested that water transfers from the Great Lakes to the American Southwest should be considered in order to serve the greatest good; water rights and export form the Great Lakes watershed is, not surprisingly, a controversial topic.
In most instances, large-scale water transfers over huge distances by pipeline or tanker are simply too expensive to make sense, or there is too much political resistance. As one extreme example, in the early 1990s, Walter Hickel (then governor of Alaska) and California congressmen Edward Roybal and George Brown requested a feasibility investigation for a pipeline that would bring water from Alaska to California through a subsea pipeline (Figure 9). The committee estimated that the cost of water transfer would be between $3000-4000 per acre-foot, or approximately triple to quadruple the cost of SWRO desalination. In the same report, the committee assessed other sources of water for California and noted that bringing water in by tanker would cost $1,500-2,000 per acre-foot for contracts of at least 30,000 acre-feet.
In other cases, the economics are not as prohibitive. For example, water is routinely transferred within California, or between Western States (e.g. Colorado River water transferred to Southern CA in the All American Canal) over distances of hundreds or even over a thousand km. This so-called “imported water” is the basis for the cost comparison of alternative supplies. At a yet larger scale, China has recently undertaken the world’s largest water transfer project, the South-to-North Water Diversion Project (or SNWDP). The main driver for the water project is that precipitation, and thus water resources, are very unevenly distributed across China (Figure 10) – and water-scarce provinces account for over 40% of the GDP. At the same time, almost a third of the population (300 million people) have access only to contaminated water – largely because of insufficient clean water supply and/or limited surface water flows that do not flush pollutants from the channel (as discussed in Module 5 – sidebar on the Three Gorges Dam).
The SNWDP will move almost 45 billion m3 of water per year (36 million acre-feet, or ~3 times the Colorado River’s flow), over distances of almost 4500 km. Although the financial benefits seemingly outweigh the costs – and hence the project is moving forward – major drawbacks are inevitable. For example, such a large water transfer is likely to have major impacts on river systems, in terms of changes in flow, sediment transport, and flushing; relocation of people along the route; construction across archeological and religious sites; and environmental impacts on wetlands that may disappear and endangerment of species that have adapted to the natural river flow regime (sound familiar? think back to Modules 3, 4, and 5!)
Links
[1] http://creativecommons.org/licenses/by-sa/3.0
[2] http://www.gnu.org/copyleft/fdl.html
[3] http://tampabaywater.org
[4] http://climate.gov
[5] https://pacinst.org
[6] https://pacinst.org/
[7] http://pacinst.org/desal-and-energy-use-should-we-pass-the-salt/
[8] http://www.hcn.org/issues/358/17328
[9] https://commons.wikimedia.org/wiki/File:China_average_annual_precipitation_(en).png#mediaviewer/File:China_average_annual_precipitation_(en).png