Using the TIN-Based Real-Time Integrated Basin Simulator (tRIBS) to Model Streamflow and Terrain Processes in the Rio Grande de Añasco, Puerto Rico
Author(s)
Huner, Fatma Ekin
Advisor(s)
Editor(s)
Collections
Supplementary to:
Permanent Link
Abstract
Rainfall–runoff models support decisions in water resources management, such as hydraulic design, planning, and flood control, especially where observations are limited in space and time. These models exist in several forms, and each has been developed for various purposes. Physically based distributed models, which solve governing physical equations, are particularly useful for representing hydrological processes in space and time, but they require greater expertise. The Triangulated Irregular Network (TIN)-based Real- time Integrated Basin Simulator (tRIBS) is one such model, and although it has been applied in various settings, additional case studies are valuable for informing its practical use. This study applies tRIBS to simulate streamflow, terrain processes, and hydrological dynamics in a clay soil-dominated, predominantly evergreen-forested subbasin of the Río Grande de Añasco in western Puerto Rico. The goals are to establish and calibrate the model, evaluate its performance across an event-based window and an extended period, and document insights on initialization, sensitivity, and calibration strategies to guide future tRIBS applications and water resources studies in the region. The model was successfully calibrated for August 2000–June 2001 and produced reasonable streamflow simulations during both the event-based (November 4–17, 2003) and long-term (September 1990–July 1991) validation periods. Performance depended strongly on precipitation patterns: watershed-wide, uniform rainfall events were captured well, whereas localized storms were more difficult to reproduce due to limitations in gauge- based rainfall representation. For this study, spin-up tests indicated that recycling the xiv hydrometeorological forcing was the most effective approach for initializing the groundwater table. The sensitivity analysis showed that saturated hydraulic conductivity in the clay- dominated study area played a critical role in controlling infiltration, groundwater, and baseflow. The pore-size distribution index was also important because it strongly affected the model response and baseflow. Lower values of this parameter substantially decreased baseflow and amplified the impact of changes in air entry pressure. Other influential soil parameters included the hydraulic decay parameter, anisotropy ratio, and saturated soil moisture. Land use parameters were less influential, although the optical transmission coefficient and stress thresholds for evaporation and transpiration had noticeable effects on model response. Model performance results are summarized as follows. For the 11-month calibration (August 2000–June 2001), hourly performance had a correlation coefficient (CC) of 0.68, a Nash–Sutcliffe efficiency (NSE) of 0.39, and a root-mean-square error (RMSE) of 11.54 m³/s. The model was validated with both a short high-rainfall window where precipitation was relatively uniform across the watershed (November 4–17, 2003) and an independent period equal in length to the 11-month calibration (September 1990 to July 1991). In the short, high-rainfall period, when rainfall was more uniform across the watershed, hourly performance showed CC 0.91, NSE 0.69, and RMSE 47.85. For the 11-month period that includes wet and dry seasons and a mix of uniform and non-uniform events, hourly performance showed CC 0.58, NSE 0.24, and RMSE 13.55. Performance improved at the daily time step: NSE and CC increased, while RMSE decreased.
Sponsor
Date
2025-12
Extent
Resource Type
Text
Resource Subtype
Thesis (Masters Degree)