Monitoring water flow, turbidity and suspended sediment load, from an Apennine catchment basin, Italy

The aim of this paper is to discuss the results of a study conducted on the monitoring of the suspended sediment load and water flow of the Sillaro torrent, during 1997-2000. The river basin is located in the Northern Apennines in the province of Bologna in Italy. Its height is from 68 to 993 in above sea level. A clayey-waterproof soil characterises the 137.6 km(2) basin surface. The mean annual precipitation is 942 mm (1962 1983). The mean annual temperature is 11.8degreesC, while the maximum, registered in July, is 22degreesC. A station for measuring the amount of sediment yield and water flow was established at the outlet from the mountain basin of the Sillaro Torrent. The monitoring station was equipped with an ultrasonic flow meter and an automatic water sampler. The flow meter measured the hydraulic level, computed the water flow and sent signal to the water sampler, so that there would be a sample of sediment yield every 100 000 m(3) of water crossing the section. The suspended sediment concentration (SSC) and the turbidity were measured on the samples, and the water samples were analysed by a laboratory turbidimeter. The best relationship between turbidity and SSC was established and applied to the turbidity of the samples so as to obtain the concentration of the suspended sediment. It was concluded that firstly, the instrumentation used for hydrologic monitoring is reliable, secondly, a simple linear regression of SSC and turbidity is adequate for an accurate estimation of the load and thirdly the multiplicative model of the suspended sediment yield on water flow is a statistically significant relationship. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.