The Future of the Chesapeake Bay Watershed Region: Coupling Socio-Economic and Earth-System Models

Urban sprawl, deforestation, and other human influences substantially alter and fragment local landscapes, significantly affecting local, regional, and global climates by changing the energy balance of Earth’s surface (Marland et al., 2003). Current efforts to combat global warming focus on reducing the emissions of greenhouse gases, but do not fully address the substantial contribution of land use to climate change (Fall et al., 2010; Yang et al., 2011). Since even relatively small changes in the order of 100 square kilometers of urban areas can change local rainfall patterns (Shepherd et al., 2002) and trigger other climate disruptions (Coutts et al., 2008), it is very important to include impacts of land use change on regional climate change in analyzing dynamics of human and natural systems (Marland et al., 2003). In addition, local socio-economic change — such as population growth and infrastructural development for public and private sector activities— will increase the pressure on local water resources and threaten the local environment further. Our research goal is to understand how climate change - in particular droughts, floods, storms, and sea level rise (Haer et al., 2013) - could affect the CBW over the next several decades under different Land-Use/Land-Cover Change scenarios as a result of socio-economic change and regional policies. Our proposed modeling framework allows us to assess the impact of different land use policies on the regional climate as well as the water and land availability across the watershed, and associated impacts in downstream socioeconomic sectors. Therefore, the research outcomes can be beneficial for scientifically informed decision making at the regional/state level.

Models Coupling Structure

MRIO Model on Land Displacement and Land Stress

Input-Output (IO) analysis is an accounting procedure that relies on national or regional input-output tables. An input-output table shows the flows of goods and services and thus the supply and demand interdependencies along the production chain within an economy. Due to the ability of input-output analysis to provide a life cycle perspective from ‘cradle to grave’ by accounting for impacts of the full upstream supply chain IOA has become an important tool in Ecological Economics and Industrial Ecology, for example being used in life-cycle analysis and for linking local consumption to global impacts along global supply chains. In a multi-regional input-output framework, different regions are connected through interregional trade. With extension of water coefficient, the MRIO model is able to capture the total direct and indirect water consumption associated with the final demand of a region and the virtual water flows to/from the region.

MRIO Model Example

COWA Model

The Coupled Water Model (COWA), developed by Motesharrei, Gustafson, and Rivas under supervision of Profs Kalnay and Miralles-Wilhelm, models both natural and human elements of regional freshwater system. COWA is a model is of intermediate complexity for the water system. COWA can simulate the future evolution of water sources and supplies under different scenarios given by the model parameters. These parameters control collection of water from the sources into the supply, transfer of water to different consumers, wastage of water through leaks, recirculation of the used water through the treatment plants, return of used water to the sources, and lost water due to runoff to the ocean and bay or due to evaporation. COWA takes into account the water consumption of five different sectors: households, industry, energy production, agriculture, and livestock and aquaculture. The demand in each sector is linked to the population and other demographic data such as per capita consumption for households and per acreage consumption for agriculture. The net demand is then calculated by considering the effectiveness of dispensing technologies in reducing the net consumption. The parameters that determine leakages and recycling are taken from the regional and national data sources.

COWA Model Framework


There are widespread concerns that current trends in resource-use are unsustainable, but possibilities of overshoot/collapse remain controversial. Collapses have occurred frequently in history, often followed by centuries of economic, intellectual, and population decline. Many different natural and social phenomena have been invoked to explain specific collapses, but a general explanation remains elusive. We build a human population dynamics model by adding accumulated wealth and economic inequality to a predator–prey model of humans and nature. The model structure, and simulated scenarios that offer significant implications, are explained. Four equations describe the evolution of Elites, Commoners, Nature, and Wealth. The model shows Economic Stratification or Ecological Strain can independently lead to collapse, in agreement with the historical record. The new dynamics of this model can also reproduce the irreversible collapses found in history. Collapse can be avoided, and population can reach a steady state at maximum carrying capacity if the rate of depletion of nature is reduced to a sustainable level and if resources are distributed equitably.

HANDY Model Example

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