Spatial variability in precipitation within the Hilton Experimental Site, Shropshire, UK (1982-2006)

Accurate precipitation measurements are essential for many hydrological and hydrogeological management strategies. Precipitation at the Hilton Experimental Site has been regularly measured since 1982. This paper summarises 157 rain gauge years of precipitation data, recorded between 1982 and 2006, using 11 rain gauges on the 0·5 hectare site. Precipitation varied markedly within the site. Precipitation totals were notably different between two adjacent rain gauges, the mean difference being 0·3% of the total. Variations in mean annual precipitation within the site were [less-than-or-eq, slanted]8%. Spatial variations in wind turbulence appeared to be the main factor influencing intra-site variability. Precipitation totals varied with gauge exposure, with surface level gauges receiving [less-than-or-eq, slanted]5·9% more precipitation than standard rain gauges, the difference being less lower down the slope. On a steep (~15° ) slope, basal sections had 2·5-7·9% more precipitation. Upper gauges received less, probably due to turbulence as increased exposure on the top of the slope resulted in precipitation being carried over the gauge orifice. Results confirm that due attention must be given to the inherent variability of precipitation amounts when calculating precipitation inputs. Copyright © 2008 John Wiley & Sons, Ltd.