Development and Integration of Sub-hourly Rainfall–Runoff Modeling Capability Within a Watershed Model

Abstract

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 4506 J. Jeong et al.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% 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.

Comparative Studies of Different Imputation Methods for Recovering Streamflow Observation

“…Therefore, the magnitude of peak streamflow in 2009 was the lowest compared to 2007 and 2008 ( Figure 6). In a previous work, SWAT tends to underestimate high peak flows, which is one of the limitations of the model [38,[43][44][45]. This is analogous to the results in Table 5, showing that SWAT performed better in 2009 while SOM was better in 2007 and 2008.…”

Análise de sensibilidade e calibração do modelo SWAT aplicado em bacia hidrográfica da região sudeste do Brasil

“…Assim, a acurácia do modelo depende, em grande parte, dos parâmetros que descrevem as características relevantes da bacia hidrográfica e do quão representativos eles são (Adriolo et al, 2008). ressalta-se que o swAt é sensível a uma gama de variáveis de entrada relacionadas a vegetação, manejo e tipo dos solos, clima, aquífero, canal e reservatório (Adriolo et al, 2008;Jha, 2009;reungsang et al, 2009;Jeong et al, 2010). devido a esse grande número de parâmetros de entrada, não é possível estudar a incerteza de todos eles.…”

Simulating Flash Floods at Hourly Time-Step Using the SWAT Model

“…The improvement in the model's performance at the sub-daily time-step is mostly due to the improvement in predicting high flows [21]. Indeed, in our study, the peak discharge is better simulated at the hourly time-step with the 15 km 2 delineation scheme.…”

“…As previously highlighted by Jeong et al [21], the sensitivity of the SWAT parameters was significantly influenced by the model operational time step. The parameters related to channel routing (CH_N2, CH_K2) were relatively more sensitive at the hourly time step, whereas the significance of groundwater flow parameters (RCHRG_DP, GWQMN) was relatively higher at the daily time interval.…”

“…Therefore, the parameters from SWAT that are involved in the GAML equation are the saturated hydraulic conductivity (SOL_K), the curve number (CN2), the soil texture (SOL_CLAY, SOL_SAND, SOL_BD) and the soil available water content (SOL_AWC). The GAML equation is a physically-based model that allows continuous simulation of the infiltration process assuming the soil profile is homogeneous and antecedent moisture is uniformly distributed in the profile [21]. The GAML method requires sub-daily precipitation data.…”