Applicability of acoustic Doppler devices for flow velocity measurements and discharge estimation in flows with sediment transport

Acoustic Doppler devices (Unidata Starflow) have been deployed for velocity measurements and discharge estimates in five contrasted open-channel flow environments, with particular attention given to the influence of sediment transport on instrument performance. The analysis is based on both field observations and flume experiments. These confirm the ability of the Starflow to provide reliable discharge time-series, but point out its limitations when sediment is being transported. (i) After calibration of the instrument by the Index Velocity Method, the deviation from reference discharge measurements was = 150 mu m) transported by way of saltation or as bedload caused a significant underestimation of velocity by as much as 50%; a slight underestimation (10-15%) was also observed when significant quantities of fine particles (<= 150 mu m) were transported in suspension; this underestimation was shown to reach 20-30% when suspended sediment concentrations were very high (c. 50-100 g L-1)

Challenges to estimate surface- and groundwater flow in arid regions: The Dead Sea catchment

The overall aim of the this study, which was conducted within the framework of the multilateral IWRM project SUMAR, was to expand the scientific basement to quantify surface- and groundwater fluxes towards the hypersaline Dead Sea. The flux significance for the arid vicinity around the Dead Sea is decisive not only for a sustainable management in terms of water availability for future generations but also for the resilience of the unique ecosystems along its coast. Coping with different challenges interdisciplinary methods like (i) hydrogeochemical fingerprinting, (ii) satellite and airborne-based thermal remote sensing, (iii) direct measurement with gauging station in ephemeral wadis and a first multilateral gauging station at the river Jordan, (iv) hydro-bio-geochemical approach at submarine and shore springs along the Dead Sea and (v) hydro(geo)logical modelling contributed to the overall aim. As primary results, we deduce that the following: (i) Within the drainage basins of the Dead Sea, the total mean annual precipitation amounts to 300 mm a(-1) west and to 179 mm a(-1) east of the lake, respectively. (ii) The total mean annual runoff volumes from side wadis (except the Jordan River) entering the Dead Sea is approximately 58-66 x 10(6) m(3) a(-1) (western wadis: 7-15 x 10(6) m(3) a(-1); eastern wadis: 51 x 10(6) m(3) a(-1)). (iii) The modelled groundwater discharge from the upper Cretaceous aquifers in both flanks of the Dead Sea towards the lake amounts to 177 x 106 m(3) a(-1). (iv) An unexpected abundance of life in submarine springs exists, which in turn explains microbial moderated geo-bio-chemical processes in the Dead Sea sediments, affecting the highly variable chemical composition of on- and offshore spring waters. The results of this work show a promising enhancement of describing and modelling the Dead Sea basin as a whole. (C) 2014 Elsevier B.V. All rights reserved