Bed elevation, bed surface grain size (D50 and D90), and water discharge- Waal, Pannerden Channel, Nederrijn, and IJssel, 1928-2020

Rijkswaterstaat has measured bed level along the Rhine branches since 1926 (Bovenrijn-Waal), 1928 (Pannerden Canal- Nederrijn), and 1941 (IJssel). The measurements were done using single beam echo sounders until 1999 and multibeam echo sounders since 1999-2002. Single beam measurements were taken at cross-sections spaced roughly 25 m apart and were averaged over 1 km. Multibeam measurements cover the river's entire length, and 100 m averaged data is provided here. Only cross-section averaged data is provided here. The error in bed elevation data (defined as two times the standard deviation) has been estimated to be up to 0.2-0.5 m until 1990; 0.2-0.3 m between 1990-1999, and 0.05-0.1 m since 1999 (Wiegmann, 2002). Water discharge data at Lobith, Waal, and IJssel have been measured by Rijkswaterstaat using Ott current meters until 1999 and acoustic Doppler current profiler (ADCP) since 2000. Uncertainty related to Ott current meter measurement is smaller than 20% and smaller than 10% for ADCP. Rijkswaterstaat has measured grain size data using digging buckets (until 1984) and grab-samplers (since 1984). We have included data from 1966, 1976, 1984, 2008, 2016, 2017, and 2020 measurement campaigns in this dataset. The samples were taken at cross-sections spaced 500 m to 1 km, with three samples (spaced 65 m) at each cross-section. The uncertainty of grain size data is high due to the high natural Spatio-temporal variability and limited spatial and temporal sampling density.

荷兰国家公共工程与水管理署（Rijkswaterstaat）自1926年起开展莱茵河支流上莱茵-瓦尔河（Bovenrijn-Waal）的河床高程（bed level）测量，1928年起启动潘讷尔登运河-下莱茵河（Pannerden Canal-Nederrijn）河段的测量，1941年起新增艾瑟尔河（IJssel）的河床高程监测。1999年以前，所有河床高程测量均采用单波束测深仪（single beam echo sounder），1999至2002年间逐步切换为多波束测深仪（multibeam echo sounder）；其中单波束测量沿间距约25米的横断面（cross-section）布设测点，数据以1公里为单元进行平均，多波束测量覆盖河流全河段，本次公开的多波束数据为100米沿程平均结果，且本数据集仅提供横断面平均后的河床高程数据。河床高程数据的不确定度（定义为两倍标准差）估算结果如下：1990年之前为0.2～0.5米，1990年至1999年间为0.2～0.3米，1999年以来降至0.05～0.1米（Wiegmann, 2002）。该机构同时对洛比特水文站、瓦尔河及艾瑟尔河的过水流量开展监测：1999年以前采用奥特流速仪（Ott current meter）进行测量，2000年起改用声学多普勒流速剖面仪（acoustic Doppler current profiler, ADCP），奥特流速仪的测量不确定度小于20%，声学多普勒流速剖面仪的测量不确定度则小于10%。该机构还采用两类工具采集沉积物粒度数据（grain size data）：1984年之前使用挖掘铲（digging bucket），1984年起改用抓斗采样器（grab-sampler），本数据集纳入了1966、1976、1984、2008、2016、2017及2020年共7轮野外测量的粒度数据；采样点沿间距500米至1公里的横断面布设，每个横断面采集3个间距为65米的沉积物样品，受自然时空变异性较强且采样的时空密度有限，该粒度数据集的不确定度较高。