DEVELOPMENT OF MODELS AND CONSERVATION PRACTICES FOR WATER QUALITY MANAGEMENT AND RESOURCE ASSESSMENTS
Location: Grassland, Soil and Water Research Laboratory
Title: Development and integration of sub-hourly rainfall-runoff modeling capability within a watershed model
| Jeong, Jaehak - |
| Kannan, Narayanan - |
| Glick, Roger - |
| Gosselink, Leila - |
| Srinivasan, Raghavan - |
Submitted to: Water Resources Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 2010
Publication Date: December 1, 2010
Citation: Jeong, J., Kannan, N., Arnold, J.G., Glick, R., Gosselink, L., Srinivasan, R. 2010. Development and integration of sub-hourly rainfall-runoff modeling capability within a watershed model. Water Resources Management. 24(15):4505-4527.
Interpretive Summary: Increasing urbanization changes runoff patterns causing increased flooding and down cutting and widening of stream channels. The Soil and Water Assessment Tool (SWAT) was modified to accurately simulate the impact of urbanization on flooding and also on management practices, such as detention structures, that are used to mitigate the impacts. The improved SWAT model provides a valuable tool for policy makers to develop strategies to alleviate the impacts of urbanization on flooding and water quality.
Increasing urbanization changes runoff patterns to be flashy and instantaneous with decreased base flow. A model with the ability to simulate sub-daily rainfall–runoff processes and continuous simulation capability is required to realistically capture the long-term flow and water quality trends in watersheds that are experiencing urbanization. Soil and Water Assessment Tool (SWAT) has been widely used in hydrologic and nonpoint sources modeling. However, its subdaily modeling capability is limited to hourly flow simulation. This paper presents the development and testing of a sub-hourly rainfall–runoff model in SWAT. SWAT algorithms for infiltration, surface runoff, flow routing, impoundments, and lagging of surface runoff have been modified to allow flow simulations with a sub-hourly time interval as small as one minute. Evapotranspiration, soil water contents, base flow, and lateral flow are estimated on a daily basis and distributed equally for each time step. The sub-hourly routines were tested on a 1.9 km**2 watershed (70 percent undeveloped) near Lost Creek in Austin Texas USA. Sensitivity analysis shows that channel flow parameters are more sensitive in sub-hourly simulations (t = 15 min) while base flow parameters are more important in daily simulations (t = 1 day). A case study shows that the sub-hourly SWAT model reasonably reproduces stream flow hydrograph under multiple storm events. Calibrated stream flow for 1 year period with 15 min simulation (R**2 = 0.93) shows better performance compared to daily simulation for the same period (R**2 = 0.72). A statistical analysis shows that the improvement in the model performance with sub-hourly time interval is mostly due to the improvement in predicting high flows. The sub-hourly version of SWAT is a promising tool for hydrology and non-point source pollution assessment studies, although more development on water quality modeling is still needed.