Integrated Ecological Economic Modeling of the Patuxent River Watershed, Maryland

Abstract

Understanding the way regional landscapes operate, evolve, and change is a key area of research for ecosystem science. It is also essential to support the “place‐based” management approach being advocated by the U.S. Environmental Protection Agency and other management agencies. We developed a spatially explicit, process‐based model of the 2352 km2 Patuxent River watershed in Maryland to integrate data and knowledge over several spatial, temporal, and complexity scales, and to serve as an aid to regional management. In particular, the model addresses the effects of both the magnitude and spatial patterns of human settlements and agricultural practices on hydrology, plant productivity, and nutrient cycling in the landscape. The spatial resolution is variable, with a maximum of 200 × 200 m to allow adequate depiction of the pattern of ecosystems and human settlement on the landscape. The temporal resolution is different for various components of the model, ranging from hourly time steps in the hydrologic sector to yearly time steps in the economic land‐use transition module. We used a modular, multiscale approach to calibrate and test the model. Model results show good agreement with data for several components of the model at several scales. A range of scenarios with the calibrated model shows the implications of past and alternative future land‐use patterns and policies. We analyzed 18 scenarios including: (1) historical land‐use in 1650, 1850, 1950, 1972, 1990, and 1997; (2) a “buildout” scenario based on fully developing all the land currently zoned for development; (3) four future development patterns based on an empirical economic land‐use conversion model; (4) agricultural “best management practices” that lower fertilizer application; (5) four “replacement” scenarios of land‐use change to analyze the relative contributions of agriculture and urban land uses; and (6) two “clustering” scenarios with significantly more and less clustered residential development than the current pattern. Results indicate the complex nature of the landscape response and the need for spatially explicit modeling.

Effects of land-use change on nutrient discharges from the Patuxent River watershed

“…The differences in TN and TP fluxes among the models seem relatively small compared to the variability among years observed for the models reporting predictions for more than 1 yr (Table 9). Load estimates were not reported for the Patuxent Landscape model, but average N concentration at Bowie for 1997 was predicted to be 11 mg N l Ϫ1 (Costanza et al 2002), well above observed average N concentrations of 2-3 mg N l Ϫ1 (Table 5 and Sprague et al 2000). The Smithsonian Environmental Research Center (SERC), CBP, and MDP models differ more in their attribution of sources and sinks of nutrients than in their average output estimates.…”

“…A Patuxent-specific version of HSPF offering more spatial detail (39 segments) and greater local calibration (9 Patuxent stations) was also developed (Aqua Terra et al unpublished data), but work was suspended before the model was thoroughly analyzed and applied. The Patuxent Landscape Model (PLM) is another model that incorporates more mechanistic detail on ecosystem processes and higher spatial resolution, using raster-based modeling to divide the Patuxent into thousands of grid cells (Voinov et al 1999;Costanza et al 2002). Like HSPF, PLM operates on a fine timescale (daily or finer) and includes hundreds of mechanistic parameters that are estimated indirectly then adjusted in model calibrations to actual watershed discharge data.…”

Group report: Global change and the European coast — climate change and economic development

“…A holistic attitude, involving integrated modelling that incorporates both natural and social sciences, is also necessary to deal with the uncertainties of the future. Spatially explicit models of river basins that incorporate economic drivers and costs are already available (e.g., Costanza et al 2002) and the development of coastal models of this type that are specific to the European context would be invaluable. Thus, the maintenance and enhancement of natural sinks and buffers in coastal zones combined with greater research into their effectiveness and limitations in ensuring human safety, economic development and ecological integrity, is clearly a necessary future goal.…”

STELLA software as a tool for modelling phosphorus removal in a constructed wetland employing dewatered alum sludge as main substrate

“…[14] It is noted that the STELLA software has been widely used in biological, ecological and environmental sciences including its application in CW. [15][16][17] As a so-called novel alum sludge-based constructed wetland system was developed in our research group, [18] and understanding P removal in the system is desirable especially for modelling and prediction purposes. This forms the basis of the study.…”