A Parameter Sensitivity Analysis Across Mesoscale Basins Entering the Gulf Mexico Basin
Abstract
Hydrologic models are tools that can quantify the natural flow regime for locations
that lack pre-disturbed flow records by matching existing measurements and translating
information from areas we have measurements to places that we don’t. With any model
application, we try to balance model complexity, the number of model parameters, with
our ability to predict a range of hydrologic processes at fine scales. To address
over-parameterization issues that arise from complex models, a sensitivity analysis
can be employed to determine which parameters are more or less important.
The objective of this study is to understand unaltered drainages in the headwater
basins of lower Alabama. To understand unaltered drainages we employed the Method
of Morris sensitivity analysis for 7 headwater sites within the Gulf of Mexico Basin.
At the headwater locations we used the Precipitation Runoff Modeling System (PRMS)
model to simulate streamflow and compared to existing measurements. The importance
of a model parameter was identified based on the mean (μ) and standard deviation (σ)
across multiple elementary effects. By analyzing parameter sensitivity with respect
to multiple metrics describing the flow regime, the sensitivity analysis allows us
to rank the importance of the 17 model parameters and understand the dominant hydrologic
process for unaltered drainages in headwater basins of lower Alabama.
In order to account for different flow regimes, performance of watershed models is
often evaluated for multiple functions that capture different parts of the hydrograph.
The evaluation functions focused on high flow, low flow, and daily flow.
Across the 7 mesoscale basins, we were able to identify the dominant parameters for
the 6 different evaluation functions. The sensitivity analysis identified 8 PRMS model
parameters as highly impactful on streamflow. These model parameters are associated
with the soil-zone, subsurface, impervious zone, and the groundwater reservoir of
the PRMS model. The main purpose of these parameters is to route water once it hits
the land surface either to the stream network or through the soil profile into the
groundwater reservoir are the controlling model parameters. Also, we were able to
determine the parameters that were considered impactful were dominated by interactions.
Due to the interactions, we have difficulty characterizing the model in terms of model
parameters because multiple parameter sets are able to produce the same model output.
Model interactions complicate the modeling effort and should be considered during
calibration. Ultimately, a sensitivity analysis is able aid in model calibration by
identifying impactful parameters and reducing the number of parameters to focus on
during calibration.
Type
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https://hdl.handle.net/10161/9650Citation
Hunt, Alexandria (2015). A Parameter Sensitivity Analysis Across Mesoscale Basins Entering the Gulf Mexico
Basin. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/9650.Collections
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