## 2 Data
### Satellite Altimetry  
Satellite altimeter data is an alternative data source for validation as it can be used also in remote areas where no gauging stations are available. For many years, satellite altimetry has been proven to have the capability of monitoring water level changes of inland waters [28; 29; 30]. Depending on the investigated inland water body, water level time series since 1992 can be achieved. In this study, we use altimeter missions ERS-2 (1995-2011), Envisat (2001-2013) and SARAL (since 2013) all characterized by the same orbit with a repeat cycle of 35 days. Additionally, the altimeter missions Topex/Poseidon (1992-2006), Jason-1 (2001-2013), Jason-2 (since 2008) and Jason-3 (since 2016) are used for the estimation of water level time series which have a repeat cycle of about 10 days. Sentinel-3A (since 2016) has a repeat cycle of 27 days and has a different orbit than the other two satellite constellations. The temporal resolution of the water level time series depends on the size and shape of the lakes. This fact influences the number of crossing satellite tracks. The temporal resolution varies between a few days for large inland waters crossed by several altimeter tracks and 35 days for small lakes crossed by only a single altimeter track (e.g., Envisat). Satellite altimetry has the potential to provide  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Band Description** & \begin{tabular}{c} **Landsat-4,-5,-7** \\ **(TM and ETM+)** \\ \end{tabular} & \begin{tabular}{c} **Landsat-8** \\ **(OLI)** \\ \end{tabular} & \
\begin{tabular}{c} **Sentinel-2A,-2B** \\ **Name** \\ \end{tabular} &
\begin{tabular}{c} **Standard** \\ **Name** \\ \end{tabular} \\ \hline Blue & Band 1 & Band 2 & Band 2 & \(BLUE\) \\ Green & Band 2 & Band 3 & Band 3 & \(GREEN\) \\ Red & Band 3 & Band 4 & Band 4 & \(RED\) \\ Near-Infrared (NIR) & Band 4 & Band 5 & Band 8 & \(NIR\) \\ Short Wave Infrared 1 (SWIR\({}_{1}\)) & Band 5 & Band 6 & Band 11 & \(SWIR_{1}\) \\ Short Wave Infrared 2 (SWIR\({}_{2}\)) & Band 7 & Band 7 & Band 12 & \(SWIR_{2}\) \\ Mask (Clouds, Shadow, etc.) & CFmask & CFmask & Fmask4.0 & \(QUALITY\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Overview of used individual and standard band names.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Lake/Reservoir** & **Station Name** & **Station ID** & **Source** \\ \hline Claiborne & Aycock & 07364840 & USGS \\ Clear & Clarence & 07352895 & USGS \\ Cooper & Cooper & 07342495 & USGS \\ Forggen & Rosshaupten & 12001301 & BEA \\ Lewisville & Lewisville & 08052800 & USGS \\ Mead & n.a. & n.a. & USGS \\ Murray & Columbia & 02168500 & USGS \\ Nova Ponte & n.a. & n.a. & ANA \\ Poco da Cruz & n.a. & n.a. & ANA \\ Ray Roberts & Pilot Point, TX & 08051100 & USGS \\ Richland Chambers & Kerens, TX & 08064550 & USGS \\ Salton Sea & Westmorland & 10254005 & USGS \\ [PERSON] & Jasper & 08039300 & USGS \\ Tavakoni & Wills Point & 08017400 & USGS \\ Toledo Bend & Burkeville & 08025350 & USGS \\ \hline \hline \end{tabular}
\end{table}
Table 2: List of used in situ stations.  
water level time series also in remote areas where no in situ stations are available. The accuracy varies between a few centimeters for large lakes and several decimeters for smaller rivers.  
In this study, water level time series of the \"Database of Hydrological Time Series of Inland Waters\" (DAHITI) developed by the \"Deutsche Geodatisches Forschungsinstitut der Technischen Universiat Munchen\" are used. The processing strategy of DAHITI is based on an extended outlier detection and a Kalman filtering approach [31]. Currently, DAHITI contains more than 1600 freely available water level time series of inland waters.