An integrated modelling system for management of the Patuxent River estuary and basin, Maryland, USA

• Published in: International journal of remote sensing 2006-09, Vol.27 (17), p.3705-3726
• Main Authors: Williams, M. R., Fisher, T. R., Boynton, W. R., Cerco, C. F., Kemp, M. W., Eshleman, K. N., Kim, S-C., Hood, R. R., Fiscus, D. A., Radcliffe, G. R.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied geophysics; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Internal geophysics; Teledetection and vegetation maps
• ISSN: 0143-1161; 1366-5901
• DOI: 10.1080/01431160500500417

The Patuxent River watershed is a heavily impacted basin (2290 km 2 ) and estuarine tributary (120 km 2 ) of the Chesapeake Bay, USA. To assist management of the basin, we are testing a coupled modelling system composed of a watershed model (HSPF), an estuarine circulation model (CH3D), and an estuarine water-quality model (CE-QUAL-ICM). The modelling system is being tested to guide the development of Total Maximum Daily Loads (TMDLs), and therefore errors in the models must be carefully evaluated. A comparison of daily total nitrogen (TN) concentrations simulated in HSPF with observations indicated that there was no significant bias, with an rms error of 37%. In contrast, modelled total phosphorus (TP) and total suspended solids (TSS) had significant bias with larger rms errors (65% and 259%, respectively). In the estuary, CH3D accurately simulated tides, temperature, and salinity. CE-QUAL-ICM overestimated nitrogen (N) and phosphorus (P) in the upper estuary and underestimated in the lower estuary, primarily because intertidal marshes are not currently a model component. Model errors declined from short (⩽1 day) to long (multi-year) timescales as under- and overestimations cumulatively cancelled. Watershed model errors propagate into the estuarine models, interacting with each subsequent model's errors, which limits the effectiveness of this TMDL management tool at short timescales.