Annotation: This paper describes an uncertainty evaluation for the measurement of water level and flow at small rivers, channels, ditches and wells all-year-round in field conditions using EHP-TEKNIKKA Measurement Systems. The EHP-TEKNIKKA Measurement Systems can be used in the different areas such as mining, water supply and water discharge, energy sector, forestry, pulp and paper, fishery and agriculture. The uncertainty of measurements must be quantified and considered in order to prove conformance with specifications and make other meaningful comparisons based on measurements. Type A uncertainties were obtained from repeatability study of the calibration process, a repeatability study of the real-time monitoring process and a system stability test. Type B uncertainties were obtained from calibration certificates and estimates.