Spatial resolutions in areal rainfall estimation and their impact on hydrological simulations of a lowland catchment

• Published in: Journal of hydrology (Amsterdam) 2018-08, Vol.563, p.319-335
• Main Authors: Terink, Wilco, Leijnse, Hidde, van den Eertwegh, Gé, Uijlenhoet, Remko
• Format: Article
• Language: English
• Subjects: Hupsel Brook catchment; Hydrological simulations; Spatial resolutions; SPHY; Uncertainty; X-band radar
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2018.05.045

•Rain gauge sampling uncertainties impact hydrologic model output in small catchments.•High-resolution radar data can be used to simulate rain gauge sampling uncertainties.•A single rain gauge in a 6.5-km2 area may sample 6 times the average hourly rainfall.•Discharge uncertainties are 60%, 20%, and 10% for 1, 10, and 40 gauges, respectively.•Uncertainties increase for larger rainfall intensities. Many studies suggest that high-density rain gauge networks are required to capture the rainfall heterogeneities necessary to accurately describe the components of the hydrological cycle. However, equipping and maintaining a high-density rain gauge network will also involve high costs. Although many studies provided useful insights on the required accuracy of rainfall estimates to accurately describe the components of the hydrological cycle, most of these studies focused on streamflow simulations, large river basins or urban environments. The objective of this study is therefore to evaluate the impact of uncertainties in areal rainfall, estimated at several spatial resolutions, on hydrological simulations of a small ∼6.5 km2 rural lowland catchment. The approach followed in this study is to force a calibrated spatially-distributed hydrological model (SPHY) with rainfall retrieved from an X-band radar and various synthetic rainfall products, calculated using bootstrap samples of a varying number of radar pixels, treated as virtual rain gauge locations within the catchment. This enables us to determine the most appropriate resolution of rainfall data to accurately describe the hydrology of a small rural lowland catchment. We found that the use of one rain gauge to estimate the catchment’s areal rainfall may lead to a potential error of more than six times the average hourly rainfall. This may lead to uncertainties in simulated discharge that approach 60% of the average hourly discharge. More than 40 rain gauges are required to reduce the potential error in areal rainfall estimation to values