Evaluating Sustainability of Projected Water Demands in 2050 under Climate Change Scenarios

More than One Out of Three U.S. Counties Face Water Shortages Due to Climate Change

More than 1,100 U.S. counties — a full one-third of all counties in the lower 48 states — now face higher risks of water shortages by mid-century as the result of global warming, and more than 400 of these counties will be at extremely high risk for water shortages, based on estimates from a new report by Tetra Tech for the Natural Resources Defense Council (NRDC).

The report uses publicly available water use data across the United States and climate projections from a set of models used in recent Intergovernmental Panel on Climate Change (IPCC) work to evaluate withdrawals related to renewable water supply.  The report finds that 14 states face an extreme or high risk to water sustainability, or are likely to see limitations on water availability as demand exceeds supply by 2050. These areas include parts of Arizona, Arkansas, California, Colorado, Florida, Idaho, Kansas, Mississippi, Montana, Nebraska, Nevada, New Mexico, Oklahoma, and Texas. In particular, in the Great Plains and Southwest United States, water sustainability is at extreme risk.

The more than 400 counties identified as being at greatest risk in the report reflects a 14-times increase from previous estimates. For a look at county- and state-specific maps detailing the report findings (including a Google Earth map), go to http://www.nrdc.org/globalWarming/watersustainability/ and http://rd.tetratech.com/climatechange/projects/nrdc_climate.asp.

While detailed modeling of climate change impacts on crop production was beyond the scope of the Tetra Tech analysis, the potential scale of disruption is reflected based on the value of the crops produced in the 1,100 at-risk counties. In 2007, the value of the crops produced in the at-risk counties identified in the report exceeded $105 billion.  A separate study compared the Tetra Tech data with county-level crop production data from the U.S. Department of Agriculture; state-specific fact sheets outlining the potential agricultural impacts may be found at http://agcarbonmarkets.com/Science.htm.

Dan Lashof, director of the Climate Center at NRDC, said: “This analysis shows climate change will take a serious toll on water supplies throughout the country in the coming decades, with over one out of three U.S. counties facing greater risks of water shortages. Water shortages can strangle economic development and agricultural production and affected communities.  As a result, cities and states will bear real and significant costs if Congress fails to take the steps necessary to slow down and reverse the warming trend. Water management and climate change adaptation plans will be essential to lessen the impacts, but they cannot be expected to counter the effects of a warming climate.  The only way to truly manage the risks exposed by this report is for Congress to pass meaningful legislation that cuts global warming pollution and allows the U.S. to exercise global leadership on the issue.”

Sujoy Roy, principal engineer and lead report author, Tetra Tech, said: “The goal of the analysis is to identify regions where potential stresses, and the need to do something about them, may be the greatest. We used publicly available data on current water withdrawals for different sectors of theeconomy, such as irrigation, cooling for power generation, and municipal supply, and estimated future demands using business-as-usual scenarios of growth.  We then compared these future withdrawals to a measure of renewable water supply in 2050, based on a set of 16 global climate model projections of temperature and precipitation, to identify regions that may be stressed by water availability.  These future stresses are related to changes in precipitation as well as the likelihood of increased demand in some regions.”

Water withdrawal will grow by 25 percent in many areas of the U.S. including the arid Arizona/New Mexico area, the populated areas in the South Atlantic region, Florida, the Mississippi River basin, and Washington, D.C. and surrounding regions.

Estimated water withdrawal as a percentage of available precipitation is generally less than 5 percent for the majority of the Eastern United States, and less than 30 percent for the majority of the Western United States. But in some arid regions (such as Texas, the Southwest, and California) and agricultural areas, water withdrawal is greater than 100 percent of the available precipitation. In other words, in many places, water is already used in quantities that exceed supply.

A summary of the report and related links are available at http://www.nrdc.org/globalWarming/watersustainability/.


Tetra Tech projected future water demand and supply.  Demand was projected based upon a business-as-usual scenario of continued population growth and associated energy and cooling water needs. Supply – or available precipitation – was estimated from current and future temperature and precipitation scenarios, obtained from an ensemble of 16 global climate models.  The analysis then compared future demand to future supply to provide an initial assessment of water resources sustainability across the nation – resolved at the county level, the best resolution for water use information – and helped identify areas most likely to be adversely impacted by increasing water demand and climate change.

The Tetra Tech report develops a new water supply sustainability index. The risk to water sustainability is based on the following criteria:  (1) projected water demand as a share of available precipitation; (2) groundwater use as a share of projected available precipitation; (3) susceptibility to drought; (4) projected increase in freshwater withdrawals; and (5) projected increase in summer water deficit.

More detailed explanations of the study methodology and water sustainability criteria can be found at  http://rd.tetratech.com/climatechange/projects/nrdc_climate.asp.

[Source: NRDC press release]

Simulating Pedestrian Movement in Dynamic Environments

Article 499, 17/05/2010 | Cybergeo, revue européenne de géographie

Arnaud Banos and Angèle Charpentier

“Agent-based simulation offers multiple advantages when dealing with complex phenomena like pedestrian movement, characterised by a possibly large number of locally interacting entities. The main goal of this article is to illustrate this key point, from the simulation of pedestrian movements in confined designed spaces. It specifically focuses on the formalisation of space and of agents populating it. The model developed, MAGE, allows exploring the role played by local interactions on the global dynamic of the designed spatial system.”

Modelling of Land Cover and Agricultural Change in Europe: Combining the CLUE and CAPRI-Spat Approaches

Agriculture, Ecosystems & Environment, Article in Press, 2010

Wolfgang Britz, Peter H. Verburg, and Adrian Leip

“Recent European research projects have developed approaches that downscale land use related results of economic models. These results are primarily downscaled from the national or regional scale to a spatial resolution appropriate for environmental impact analysis. Different studies represent the interactions between the economic and geographic components of the land system in different ways. This paper explores how interactions between economic and geographic aspects of the land system can be strengthened in modelling studies. It does so by comparing two existing approaches (CLUE and Capri-Spat) for the European Union (EU27). CLUE focuses on disaggregating national level changes in claims for agricultural and urban area to a 1 km × 1 km grid, explicitly addressing consequences of changing demands for agricultural and urban area for other land uses such as (semi-) natural vegetation. Whereas, CAPRI-Spat is concerned with agricultural land use, disaggregating cropping shares, animal stocking densities, yield and agricultural input use for mapping units. The mapping units are clusters of 1 km × 1 km pixels considered homogenous in terms of soil, slope, land cover and administrative region. This paper discusses differences between the two models relating to geographical units, distribution algorithm and most importantly diverging interpretation of ‘agricultural land’, in relationship to their respective concepts and objectives. It concludes that a stronger integration of the geographic and economic aspects can be achieved by linking the overall land use dynamics simulated by CLUE to the detailed representation of the agricultural sector by CAPRI-Spat. Therefore, relative changes in land use classes at 1 km × 1 km resolution obtained from CLUE simulations update a priori means in CAPRI-Spat entering a Highest Posterior Density Estimator. The findings of this study contribute to our overall capacity to integrate approaches from different disciplines in the integrated analysis of land change and the ex ante assessment of environmental and economic effects of agricultural policies.”

The Digital Earth: 12 Years Later

Vice President Al Gore delivered a forward-looking speech titled “The Digital Earth: Understanding our Planet in the 21st Century” at the California Science Center in Los Angeles on 31 January 1998.  Regardless of how you feel about Al Gore, every geospatial professional should read this once in a while – to both congratulate ourselves on how much progress we’ve made, and remind us there is still work to be done.

“A new wave of technological innovation is allowing us to capture, store, process and display an unprecedented amount of information about our planet and a wide variety of environmental and cultural phenomena. Much of this information will be “georeferenced” – that is, it will refer to some specific place on the Earth’s surface.

“I believe we need a “Digital Earth”. A multi-resolution, three-dimensional representation of the planet, into which we can embed vast quantities of geo-referenced data.”

You can read Gore’s complete speech here [PDF]

For a good overview of what’s happened in the last 12 years, see Digital Earth on Wikipedia

Indoor Routing for Individuals with Special Needs and Preferences

Transactions in GIS, Volume 14 Issue 3, June 2010, p 299-329

Hassan A. Karimi and Mahsa Ghafourian

“Recently much research has been focused on developing techniques and systems for providing routes within buildings. While outdoor routing is based on criteria such as shortest, fastest and least turns, indoor routing is primarily based on accessibility and safety criteria, and while outdoor routing could adversely be impacted by weather and traffic, among other conditions, such conditions do not affect indoor routing. However, developing techniques that meet user’s indoor routing preferences, especially those with special needs, is a challenging task. An example is development of a set of techniques that avoids a hallway with a protruding object to allow safe passage by the visually impaired or that avoids stairs for the mobility impaired. In this article, we present and analyze new techniques based on the Americans with Disabilities Act (ADA) standards that provide routes within buildings and meet user’s special needs and preferences.”

3-D Visualizations of Coastal Bathymetry by Utilization of Airborne TOPSAR Polarized Data

International Journal of Digital Earth, Volume 3, Issue 2 June 2010 , pages 187 – 206

Maged Marghany; Arthur P. Cracknell; and Mazlan Hashim

“Multi-frequency C and L bands in the TOPSAR data have been utilized to reconstruct three-dimensional (3-D) bathymetry pattern. The main objective of this study is to utilize fuzzy arithmetic to reduce the errors arising from speckle in synthetic aperture radar (SAR) data when constructing ocean bathymetry from polarized SAR data. In doing so, two 3-D surface models, the Volterra algorithm and a fuzzy B-spline (FBS) algorithm, which construct a global topological structure between the data points, were used to support an approximation to the real surface. Volterra algorithm was used to express the non-linearity of TOPSAR data intensity gradient based on the action balance equation (ABC). In this context, a first-order kernel of Volterra algorithm was used to express ABC equation. The inverse of Volterra algorithm then performed to simulate 2-D current velocities from CVV and LHH band. Furthermore, the 2-D continuity equation then used to estimate the water depth. In order to reconstruct 3-D bathymetry pattern, the FBS has been performed to water depth information which was estimated from 2-D continuity equation. The best reconstruction of coastal bathymetry of the test site in Kuala Terengganu, Malaysia, was obtained with polarized L and C bands SAR acquired with HH and VV polarizations, respectively. With 10 m spatial resolution of TOPSAR data, bias of -0.004 m, the standard error mean of 0.023 m, r 2 value of 0.95, and 90% confidence intervals in depth determination was obtained with LHH band.”

Spatial Analysis of Species Diversity in Pastures Using GIS and GPS Technologies

Iowa State University, Rhodes Research and Demonstration Farm Report # ISRF00-39

John A. Guretzky and Ken J. Moore

“The Rhodes research farm with its large topographic variability and extensive pasture acreage is an ideal site to evaluate the application of precision agriculture technologies to forage production and management. In previous studies at Rhodes it has been shown that forage legumes are adapted to sites with higher slopes (15 – 20%), and increasing species diversity with legumes at these sites improves productivity and forage quality. In the current study we are using global positioning systems (GPS) and geographic information systems (GIS) technologies to describe and map the spatial variability in pasture vegetation and examine its relationship to maps generated for slope, drainage, and electrical conductivity. Our objective is to determine whether these technologies can be used successfully to predict grass and legume distribution within the pastures based on topography and soil properties.”