April 2009, Vol. 21, No.4


Adapting to Climate Change in the Absence of A General Unified Theory

G. Tracy Mehan III

Notwithstanding the differing views on the ultimate causes of climate variability — with its attendant drought, rising sea levels, disruption of natural flow regimes, diminished snowpack, more intense precipitation, and increased polluted runoff — adaptation is a program water utility managers should rally around. The challenges of climate change are real, immediate, and extremely daunting whether you manage water and wastewater utilities west or east of the 100th Meridian.

Information Is a Fundamental Component of Adaptation
In the February 2008 issue of Science magazine, an article appeared with the arresting title, “Stationarity Is Dead: Whither Water Management?” (www.sciencemag.org, Vol. 319, pp. 573–574). In it, the authors argued that water management systems throughout the developed world were designed and operated under the assumption of “stationarity” — the idea that natural systems fluctuate within an unchanging envelope of variability. While the stationarity assumption often was compromised by human disturbances and even some natural climate changes in the past, planners were able to account for these, given the relatively small degree of change and variability. They could still utilize stationarity-based design.

But the authors say that due to “the magnitude and ubiquity of the hydroclimatic change apparently now under way … we assert that stationarity is dead and should no longer serve as a central, default assumption in water-resource risk assessment and planning. … Stationarity cannot be revived. Even with aggressive mitigation, continued warming is very likely, given the residence time of atmospheric [carbon dioxide] and the thermal inertia of the Earth system.”

The authors echo recent recommendations by such groups as the Water Utility Climate Alliance pointing to the urgency of downscaling global climate models to the watershed or community scale.

Water quantity and quality monitoring are essential parts of the research and development agenda, too. “Modeling should be used to synthesize observations; it can never replace them,” argue the authors of “Stationarity Is Dead.”

Failure to adequately fund, for example, stream gauging and ambient water quality monitoring, at multiple scales, is no longer something we can afford. Traditionally, monitoring is the first thing to be cut in budgetary hard times. It should be the last.

Adaptation Is an Integrating Principle of Water Management
Water law, policy, and management are segmented into impossibly neat, discrete categories: point versus nonpoint sources; groundwater versus surface water; land versus water; quantity versus quality versus flow. Managing across political boundaries and overlapping levels of government complicate matters even more.

For years, water managers have battled to overcome this fragmentation of what should be a comprehensive, integrated approach to managing water and the surrounding landscape.

Call it an ecosystem or watershed approach, integrated water or watershed resources management, total water management, or sustainable water management — it is hardly a new vision, albeit one long denied in the United States.

The great western explorer of the Colorado River and second director of the U.S. Geological Survey, John Wesley Powell, recognized the importance of watersheds, as evidenced by this statement he made to the Montana Constitutional Convention in 1889: “I think each drainage basin in the arid land must ultimately become the practical unit of organization, and it would be wise if you could immediately adopt a county system which would be convenient with drainage basins.”

Climate change and the imperative of adapting to it are accelerating this trend in the direction of a comprehensive, integrated mode of managing water resources and utilities.

For instance, in recent years, scientists have come to appreciate the importance of the natural flow regime, which is the master variable in terms of the ecological health of a river or stream. Dams, diversions, levees, and other structural interventions disrupt water flow and, just as importantly, the transport of sediment that nourishes floodplains, deltas, and estuaries.

Overconsumption of water, even in New England, can destroy a stream in the dry season.

Impervious surfaces and the loss of vegetated cover are the primary causes of urban stream syndrome, which is characterized by flash flooding, elevated nutrient and contaminant levels, altered stream morphology, sedimentation from eroded stream banks, and loss of species diversity. These conditions are indicative of a seriously altered flow regime.

The entire spectrum of urban wet weather issues — combined-sewer overflows, stormwater runoff, and even blending — are in substantial part the result of disrupted flow regimes. These altered flow regimes prevent retention of water onsite, as well as the infiltration and evapotranspiration that would filter out pollutants, regulate water releases over time, and allow for groundwater recharge. Progressive utilities and communities look to transform their urban environments with green roofs, trees, constructed wetlands, vegetated curb extensions, and rain gardens at a scale sufficient to reduce wet weather flows, provide habitat, and enhance the quality of life for citizens.

Trees and Trusts Are Water Management Tools
Focusing on trees and forests showcases the need for new tools, new skills, and new partnerships that must be cultivated by utility managers in an era of climate variability and drought.

In 2002, the Trust for Public Land (San Francisco) and the American Water Works Association (Denver) conducted a study of 27 water suppliers and found, unsurprisingly, that more forest cover in a watershed results in lower treatment costs. According to the study, Protecting The Source: Land Conservation and the Future of America’s Drinking Water, for every 10% increase in forest cover in the source area, treatment and chemical costs decreased approximately 20%. Almost 50% to 55% of the variation in treatment costs can be explained by the percentage of forest cover in the source area.

There is great potential for creative partnerships between land and water trusts and water and wastewater utilities for purposes of water quality, climate adaptation, and restoration of flow regimes.

According to the Land Trust Alliance (Washington, D.C.), private land trusts now protect an area more than 16 times the size of Yellowstone National Park, having doubled their protected acreage from 2000 to 2005. The Milwaukee Metropolitan Sewerage District has partnered with The Conservation Fund (Arlington, Va.), a prominent national land trust, to acquire and restore 730 ha (1800 ac) of floodplain as part of its flood and wet weather management efforts.

According to the Property and Environment Research Center (Bozeman, Mont.), water trusts, such as the Oregon Water Trust (Portland), which lease or purchase water rights in 11 western states for purposes of flow augmentation, have spent more than $300 million (adjusted for inflation) since 1998, four times the amount spent between 1990 and 1997. If this movement follows the same trajectory as land trusts, water trusts could become a key partner in adapting to climate variability in the West and Northwest.

Another example of this new approach is that of Clean Water Services, the public utility in Hillsboro, Ore., which is reforesting tributaries of the Tualatin River as a cost-effective means of achieving its National Pollutant Discharge Elimination System permit targets for temperature and generating multiple environmental benefits on a watershed scale.

The Denver water utility is now intensely engaged in forestry matters because of the threat of forest fires and sedimentation running off into reservoirs, thereby generating tremendous dredging costs.

In July 2008, the National Research Council of the U.S. National Academies issued a significant report, Hydrologic Effects of a Changing Forest Landscape. According to the report, streamflow from forests provides two-thirds of clean water supply in the United States.

Whether you are working with landscape architects on green infrastructure and low-impact development or with foresters at the landscape scale, utility managers will have to make new friends in order to cope with a changing climate.

Adaptation, Resilience, and Overcoming Old Dichotomies
The paramount objective is to adapt to an uncertain or nonstationary environment and make our watersheds and utilities more resilient in the face of a changing climate. This will require a multifaceted approach that overcomes old dichotomies within the water sector and beyond.

We must invest in more and better data, information, and modeling. We have to manage the landscape to manage water effectively and capture multiple environmental benefits, not just attain traditional regulatory targets, say, for water quality. We must pursue demand-side strategies as much as those on the supply side, including full-cost and conservation-based pricing.

New technology that enables more extensive water reuse and recycling, such as microfiltration, membrane technology, reverse osmosis, and ultraviolet light, also will be a part of the mix. Effective management of the watershed and the utility, as well as relations with the surrounding community and ratepayers, will be crucial.

Adaptation to climate change can serve as the integrating principle for a comprehensive, integrated approach to managing land and water for the benefit of water and wastewater utilities and their customers.  

G. Tracy Mehan III is a principal in the Arlington, Va., office of The Cadmus Group Inc. (Boston).