Spatial and Temporal Scale Effect in Simulating Hydrologic Processes in a Watershed

Abstract

Small-scale variations of hydrologic processes both in space and time have a significant impact on the simulation of hydrologic processes at different scales in the watershed. The objectives of this study were to investigate: (1) how the spatial and temporal grid scales affect the results of hydrologic process simulations; and (2) how the variability of input driving parameters (e.g., elevation and precipitation intensity) at different grid scales is related to the simulated discharge response. A hydrologic model system (HMS) was used to simulate hydrologic processes at different spatial and temporal grid scales in a small watershed. The spatial distributions of various hydrologic properties, such as soil and land-use/land-cover data, were included in the simulations along with a digital elevation model (DEM) and precipitation data. 5-min precipitation records collected from four gauge stations within the watershed were used to drive fifty model simulations, which were designed to examine the effects of grid size change and different parameterization schemes on hydrologic responses. Simulation results showed that small-scale variations in elevation and precipitation both in space and time have significant impacts on the streamflow hydrograph and the discharge volume. Results illustrated that the grid scale effect on the hydrologic response is highly correlated to the variability of elevation and precipitation at the corresponding scales; and therefore, the variations in elevation and precipitation are strong indications of the hydrologic response in the watershed.