Description: Inland Water Remote Sensing Validation Campaign 2017

Description: We simulated an experimental summer storm in large-volume (~1200 m3, ~16m depth) enclosures in Lake Stechlin (https://www.lake-lab.de) by mixing deeper water masses from the meta- and hypolimnion into the mixed layer (epilimnion). The mixing included the disturbance of a deep chlorophyll maximum (DCM) which was present at the same time of the experiment in Lake Stechlin and situated in the metalimnion of each enclosure during filling. Size-fractionated (0.2-3 µm and 〉3.0 µm) chlorophyll a (Chla) development was monitored for 42 days after the experimental disturbance event. Mixing disrupted the thermal stratification, increased concentrations of dissolved nutrients and CO2 and changed light conditions in the epilimnion. Thereby, mixing increased the concentration of Chla of the small size fraction 0.2-3.0 within one week after mixing. After 2-3 weeks, mixing resulted in increased concentrations of Chla also in the large size fraction, which was associated to a bloom of Dolichospermums sp.

Description: We simulated an experimental summer storm in large-volume (~1200 m3, ~16m depth) enclosures in Lake Stechlin by mixing deeper water masses from the meta- and hypolimnion into the mixed layer (epilimnion). The mixing included the disturbance of a deep chlorophyll maximum (DCM) which was present at the same time of the experiment in Lake Stechlin and situated in the metalimnion of each enclosure during filling. Water physical variables and water chemistry was monitored for 42 days after the experimental disturbance event. Mixing disrupted the thermal stratification, increasing concentrations of dissolved nutrients and CO2 and changing light conditions in the epilimnion. Mixing, thus, stimulated phytoplankton growth, resulting in higher particulate matter concentrations of carbon, nitrogen and phosphorous.

Description: Water isotopes (δ2H and δ18O) were analyzed in samples collected in lakes associated to major riverine systems in northeastern Germany throughout 2020. This sub-dataset is derived from water samples collected from lake shores. Samples were taken in March and July 2020 with a pipette from 40-60 cm depth below water surface and directly transferred into a measurement vial. Stable isotope analysis was conducted at IGB Berlin, using a Picarro L2130-i cavity ring-down spectrometer. The data give information about the seasonal isotope amplitude in the sampled lakes and about spatial isotope variability in different branches of the associated riverine systems.

Description: We simulated an experimental summer storm in large-volume (~1200 m3, ~16m depth) enclosures in Lake Stechlin (https://www.lake-lab.de) by mixing deeper water masses from the meta- and hypolimnion into the mixed layer (epilimnion). The mixing included the disturbance of a deep chlorophyll maximum (DCM) which was present at the same time of the experiment in Lake Stechlin and situated in the metalimnion of each enclosure during filling. Water physical variables and water chemistry was monitored for 42 days after the experimental disturbance event. Mixing disrupted the thermal stratification, increased concentrations of dissolved nutrients and CO2 and changed light conditions in the epilimnion. Mixing stimulated phytoplankton growth, thus, resulting in a bloom of Dolichospermum sp. and thereafter increased biomass of Bacillariophyceae. Subsequent, break down of both phytoplankton groups resulted in higher particulate matter sinking fluxes of particulate organic carbon (POC), total particulate nitrogen (TPN) and total particulate phosphorous (TPP) 4-5 weeks after the disturbance event. Mixing resulted in average increases in elemental downward fluxes of 9% POC, 14% total particulate Nitrogen (TPN) and 19% TPP by the end of the experiment (42 days) (n.control=4, n.mixed=4).

Description: Water isotopes (δ2H and δ18O) were analyzed in samples collected in lakes associated to major riverine systems in northeastern Germany throughout 2020. This sub-dataset is derived from water samples taken at buoys temporarily installed in deep parts of the lake. Samples were taken monthly to bimonthly from March to October 2020. A Limnos water sampler was used to obtain samples from 1 m below water surface. Isotope analysis was conducted at IGB Berlin, using a Picarro L2130-i cavity ring-down spectrometer. Water temperatures were measured in similar depths with an Aqua TROLL 600 multiparameter sonde (In-Situ, Fort Collins, CO, USA). The data give information about the seasonal isotope amplitude in the sampled lakes and about spatial isotope variability in different branches of the associated riverine systems.

Description: Water isotopes (δ2H and δ18O) were analyzed in samples collected in lakes associated to major riverine systems in northeastern Germany throughout 2020. This sub-dataset is derived from water samples taken at multiple spatially distributed spots in four selected lakes. A Limnos water sampler was used to obtain samples from 1 m below water surface on 29th and 30th September 2020. Isotope analysis was conducted at IGB Berlin, using a Picarro L2130-i cavity ring-down spectrometer.

Description: In this measurement campaign of five water bodies (lakes and reservoirs) several German research groups organised a joint effort to collect a data set for testing, evaluating, and potentially improving the abilities of satellite-based monitoring of water quality in standing waters. The strategy of the campaign is summarised in Figure 1 (documentation "Conceptual design of Inland Water Remote Sensing Validation Campaign 2017") and consists of three independently measured categories of data: (i) satellite-based monitoring, (ii) in situ monitoring, and (iii) bio-optical characterisation. The latter aspect, in particular, was intended in order to go beyond classical comparison of satellite-based and in-situ observations and to enable a more process-oriented and physically-based assessment of the observations made during the satellite overcasts. We concentrated our work on one week in summer 2017 and organised a synoptically measurement campaign on five lakes in Central Germany (Lake Arendsee, Lake Geiseltalsee, Kelbra Reservoir, Rappbode Reservoir, Lake Süßer See, see Tab. 1 in documentation "Main physical and limnological characteristics of the five water bodies from Inland Water Remote Sensing Validation Campaign 2017") based on various field and lab methods. The synoptically approach required the equipment of five sampling teams that are able to work independently from each other. Field- instruments used during the campaign (which required to be available in five sets) had been compared with each other in a separate intercalibration day. All lab-based measurements took place at the central lab of the Helmholtz-Centre for Environmental Research in Magdeburg using methods as outlined in Friese et al. (2014). The five water bodies were intentionally chosen because they reflect a broad range of temperate standing waters with respect to size, depth, trophic state, and the occurrence of cyanobacterial blooms. In addition, also natural and artificial water bodies are reflected by this set of lakes/reservoirs. To our knowledge, this is one of the rare multiple-teams efforts in remote sensing research on water quality making the collection of data in terms of their synoptic evaluation and broad methodological basis particularly useful and valuable.

Description: Kelbra Reservoir is a shallow lowland reservoir (approx. 35 Mio. m³ volume; max. depth 5,5 m, mean depth 3.5 m; surface area 600 ha), which was constructed 1962-1966 for flood protection for the downstream reaches of the river “Helme” and came into operation 1969. It is also used for irrigation and recreational purposes. Until the beginning of the 1990s, the production of carp was also initiated and played an important role (Ziemann 1986). Immediately after commissioning, the reservoir became an important resting place for diverse migrating birds (Görner et al. 1983; Scheuer 2003). In the last 30 years, cranes, during their migration from Scandinavia to Africa, occurred in high numbers (up to 10,000 individuals; Höpfner 2003; Scheuer et al. 2019) so that bird protection measures became a vital component of the reservoir management. During winter, the reservoir is emptied to have its full capacity for flood protection. The highest floods occur in river “Helme” typically from December through March (LHW 2016). Kelbra Reservoir has been highly eutrophic from the very beginning (Ziemann 1986) until now although waste water treatment was improved and carp production was stopped in the 1990s. Still, external and internal phosphorus loading is at a high level. Due to very high total phosphorous concentrations cyanobacterial blooms appear regularly in summer time and the trophic state can be characterized to be hypertrophic. This publication series includes datasets collected on Kelbra Reservoir during the Inland Water Remote Sensing Validation Campaign 2017 (Bumberger et al. 2023).

Description: On Aug. 29, 2017, the central intercalibration campaign was conducted on Lake Süßer See, in which all groups were participating that had been involved in the field measurements included in the overall project campaigns. The main goal of this intercalibration campaign was to realise a direct comparison of all involved field and lab sensors/analysis in order to assess their accuracy, comparability, and reproducibility. For this purpose, all used instruments were used simultaneously at the measuring point on Lake Süßer See. This fully parallel application enabled us to directly compare the results under identical in-situ conditions and to detect and quantify instrumental deviations.