Changing Planet

Building a Resilient Water Portfolio

A collection of water strategies reduces risk. (Photo collage by Robert B. Sowby)

By Robert B. Sowby

People often ask me, “So what’s the answer to the world’s water problems?” and expect an easy, digestible response. But there is no silver bullet. While most water plans have a dominant component, dependence on a single strategy is risky. Climate change, population growth, and other 21st-century challenges can adversely impact regions with few water options. Rather, we should think in terms of a water portfolio.

Like stocks and energy, a diverse water portfolio—a deliberate collection of assets, policies, practices, and technologies—is the best long-term option. A portfolio is designed with considerations for cost, applicability, time, and objectives.

Some strategies, like water conservation, have short-term benefits that buy us time to consider long-term issues. Others, such as groundwater recharge, are investments that pay off only over time. Some are better at different times of year or in different places. Tradeoffs are inevitable since each has its own strengths and weaknesses, but a portfolio still has a collectively lower risk than any individual component. This is the essence of the proverb, “Don’t put all your eggs in one basket.” Might I suggest: “Don’t get all your water from one bucket.”

Water strategies vary around the world, and looking globally, we can learn how to build our water portfolio locally. Utah relies on snowmelt captured in hundreds of mountain reservoirs. Energy-rich, water-poor countries like the United Arab Emirates can afford the high energy requirements of desalination. Densely populated Singapore is known for NEWater, its brand-name reclaimed wastewater that shortcuts the urban water cycle. Aquifer storage and recovery has been successful in several states and countries. Villages in Africa and throughout the world harvest rainwater, which is clean and suitable for many applications.

Here are a few ideas to consider when developing a water portfolio.

Stormwater. Transform stormwater from a waste product into a resource by techniques of low-impact development (LID). Possibilities include minimizing impervious areas and establishing rain gardens, permeable pavements, native vegetation, and engineered wetlands. Dual-use facilities are catching on, such as a soccer field detention pond, or even a stormwater skate park like one in Denmark that provides fun and prevents flooding. Rethinking how we handle stormwater in urban areas can realize benefits in flood control, water quality, and aesthetics.

Surface water. Surface waters such as lakes, reservoirs, and rivers are the most visible sources and are often tapped for public water supply. Since the open nature of surface water exposes it to pollutants, it must be thoroughly treated before human consumption. Surface waters also perform critical environmental functions that must be balanced with human appropriation.

Groundwater. Groundwater exists almost everywhere at some depth. Where not otherwise contaminated, groundwater is safer, with fewer pathogens and higher overall quality. However, groundwater takes centuries to be replenished, and overuse can cause irreparable damage.

Reclaimed water. Recycle treated wastewater for specific suitable uses in industry or agriculture. The regulatory framework on this issue is still developing, as is public opinion. If the treated water quality exceeds the natural source quality, reclaimed water is an economically sensible option.

Greywater. In commercial or institutional settings, reapply mildly used water from showers or sinks on-site for landscaping or toilet flushing.

Rainwater harvesting. Capture precipitation from roofs and store it for later use. Rainwater is relatively clean and is suitable for outdoor uses. In commercial developments, harvested rainwater can be used to flush toilets or wash cars. In urban and residential areas, rainwater harvesting reduces municipal water demands, preserves water quality, and decreases storm runoff.

Artificial recharge. Augment groundwater supplies with surface water. During wet periods, excess water from certain surface sources may be artificially infiltrated or injected into aquifers to store water for dry periods, or simply to supplement groundwater storage over time. Artificial recharge (AR) and aquifer storage and recovery (ASR) have been effective in areas with distinct hydrologic seasons.

Conservation. Reduce water use across industrial, agricultural, residential, and commercial sectors. While conservation may not avoid capital projects, in can defer them long enough to make better decisions.

Allocation. Where possible, match a water source to its intended use. Drinking water has high quality standards, but is often used for outdoor irrigation where lower-quality water would suffice. Consider the end-use requirements and allocate resources that best fit that end use.

Policy. Develop forward-looking, data-based, water-aware policies with public support. Regulation and policy can help or hinder application of any water strategy. Recent cases, such as one in Arkansas, demonstrate how public involvement allows water projects to be planned, funded, and executed locally, all with better results and lower costs.

These ideas and many more can fortify a water portfolio. Each one’s feasibility will need to be assessed for specific situations, and innovation and research will continue to produce new options. A resilient water portfolio is the best answer to our future water challenges.

Robert B. Sowby is a hydrologist and consulting engineer in Salt Lake City and currently serves as editor of the Utah Water Blog.

  • Ima Ryma

    Pollution and climate change will
    Destroy the waters on the Earth.
    In the end, life forms’ thirst will kill.
    No fire or ice – for what it’s worth.
    Water will flow with human greed.
    Haves will have and have nots will not.
    Governments will use the dire need
    To cling onto power they’ve got,
    Until even elites drink dry
    Because of profit “policy,”
    Some elites may even ask why,
    As the thirstier they do be.

    Water, water – oh where, oh where?
    There’s not a drop to drink – soon there!

  • Tim Peterson

    It’s good to see that hydrological resilience is starting to get some attention. However, in the post the meaning of ‘resilience’ is very vague and it misses the point that resilience has one of two very specific technical meanings: (1) the existence of multiple steady states for the same climate, landuse etc (i.e Holling’s resilience); or (2) the existence of only one steady state and the return time following a disturbance (Pimm’s resilience). If anyone is interested to find out more see the following papers (contact me if you need copies):

    Peterson, T. J., and A. W. Western (2014), Multiple hydrological attractors under stochastic daily forcing: 1. Can multiple attractors exist?, Water Resour. Res., 50, doi:10.1002/2012WR013003.

    Peterson, T. J., A. W. Western, and R. M. Argent (2014), Multiple hydrological attractors under stochastic daily forcing: 2. Can multiple attractors emerge?, Water Resour. Res., 50, doi:10.1002/2012WR013004.

    Peterson, T. J., A. W.Western, and R. M.Argent (2012), Analytical methods for ecosystem resilience: A hydrological investigation, Water Resour. Res., 48, W10531, doi:10.1029/2012WR012150.

    Peterson, T. J., R. M. Argent, A. W. Western, and F. H. S. Chiew (2009), Multiple stable states in hydrological models: An ecohydrological investigation, Water Resour. Res., 45, W03406, doi:10.1029/2008WR006886.

    If you want to know more about general Holling’s resileince see:

    Marten Scheffer, Steve Carpenter, Jonathan A. Foley, Carl Folke & Brian Walker (2001), Catastrophic shifts in ecosystems, Nature 413, 591-596 (11 October 2001) | doi:10.1038/35098000

  • S.J. Hayduke

    I believe the author uses “resilient” in the more common non-technical context – able to withstand and/or recover from various challenges without permanent damage – which is definitely desirable for water supplies.

    A good introduction to the topic for general readers.

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