Development of operational forecasting models for hydrological events requires large-scale modeling approach and integration of various physical components and interactions in the model. Additionally, these modeling systems rely on a significant amount of pre-processing efforts in terms of model parametrization. The NOAA National Water Model (NWM) is a recent example of a large hydrologic system with the primary goal of developing an operational framework for streamflow forecasting in the Contiguous United States (CONUS) domain. The NWM latest version (i.e., v2.1) includes 5,781 lakes/reservoirs (referred to as waterbodies) in the CONUS domain with a variety of geophysical attributes and outflow conditions (managed vs unmanaged). Major datasets that currently support features of the NWM rivers and waterbodies are based on the National Hydrography Dataset Plus (NHD+), United States Army Corps of Engineers (USACE), River Forecast Center (RFC), and USGS. However, our assessment of the model performance below managed reservoirs underscores the need for revision of the waterbodies geometry and discharge characteristics.

In this study, we investigate the sensitivity of outflows and water balance calculation of the NWM waterbodies to different geometric conditions such as different shape options and head-area-volume (h-A-V) relationships. We also further investigate the discharge characteristics of these waterbodies (e.g., weir and orifice parameters) and their impact on the streamflow prediction in the NWM. We validate different scenarios of geometric and discharge characteristics of the waterbodies against streamflow observations from a selected set of downstream USGS stations.

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Development of operational forecasting models for hydrological events requires large-scale modeling approach and integration of various physical components and interactions in the model. Additionally, these modeling systems rely on a significant amount of pre-processing efforts in terms of model parametrization. The NOAA National Water Model (NWM) is a recent example of a large hydrologic system with the primary goal of developing an operational framework for streamflow forecasting in the Contiguous United States (CONUS) domain. The NWM latest version (i.e., v2.1) includes 5,781 lakes/reservoirs (referred to as waterbodies) in the CONUS domain with a variety of geophysical attributes and outflow conditions (managed vs unmanaged). Major datasets that currently support features of the NWM rivers and waterbodies are based on the National Hydrography Dataset Plus (NHD+), United States Army Corps of Engineers (USACE), River Forecast Center (RFC), and USGS. However, our assessment of the model performance below managed reservoirs underscores the need for revision of the waterbodies geometry and discharge characteristics.

In this study, we investigate the sensitivity of outflows and water balance calculation of the NWM waterbodies to different geometric conditions such as different shape options and head-area-volume (h-A-V) relationships. We also further investigate the discharge characteristics of these waterbodies (e.g., weir and orifice parameters) and their impact on the streamflow prediction in the NWM. We validate different scenarios of geometric and discharge characteristics of the waterbodies against streamflow observations from a selected set of downstream USGS stations.

**[Access the Conference Proceedings Paper on ASCE Library](https://doi.org/10.1061/9780784483466.050)** 

Improvement of Lake and Reservoir Parametrization in the NOAA National Water Model

Created in 1999, the Environmental & Water Resources Institute (EWRI) is the recognized leader within ASCE for the integration of technical expertise and public policy in the planning, design, construction, and operation of environmentally sound and sustainable infrastructure impacting air, land and water resources.

[Paper Proceedings](https://doi.org/10.1061/9780784483466)

Conference DOI: https://doi.org/10.26226/m.6329c39b68fb0e00131f77d2