Characterization of SWOT Water Level Errors on Seine Reservoirs and La Bassée Gravel Pits: Impacts on Water Surface Energy Budget Modeling

Abstract

The Surface Water and Ocean Topography (SWOT) space mission will map surface area and water level changes in lakes at the global scale. Such new data are of great interest to better understand and model lake dynamics as well as to improve water management. In this study, we used the large-scale SWOT simulator developed at the French Space National Center (CNES) to estimate the expected measurement errors of the water level of different water bodies in France. These water bodies include five large reservoirs of the Seine River and numerous small gravel pits located in the Seine alluvial plain of La Bassée upstream of the city of Paris. The results show that the SWOT mission will allow to observe water levels with a precision of a few tens of centimeters (10 cm for the largest water reservoir (Orient), 23 km2), even for the small gravel pits of size of a few hectares (standard deviation error lower than 0.25 m for water bodies larger than 6 ha). The benefit of the temporal sampling for water level monitoring is also highlighted on time series of pseudo-observations based on real measurements perturbed with the simulated noise errors. Then, the added value of these future data for the simulation of lake energy budgets is shown using the FLake lake model through sensitivity experiments. Results show that the SWOT data will help to model the surface temperature of the studied water bodies with a precision better than 0.5 K and the evaporation with an accuracy better than 0.2 mm/day. These large improvements compared to the errors obtained when a constant water level is prescribed (1.2 K and 0.6 mm/day) demonstrate the potential of SWOT for monitoring the lake energy budgets at global scale in addition to the other foreseen applications in operational reservoir management.

Hydrodynamic relationships between gravel pit lakes and aquifers: brief review and insights from numerical investigations

“…More investigation is needed to obtain valid estimations of the magnitude and seasonal distribution of open water evaporation in the particular case of gravel pit lakes. In this respect, state-of-the-art thermodynamic lake models [Ottlé et al, 2020] or isotope mass balance models [Gibson, 2002] should prove useful in estimating the evaporation losses. A generalisation of studies on gravel pit lakes to any type of climatic context is also awaited, as well as a broad assessment of how groundwater-gravel pit lake interactions may be modified as a result of climate change, following the pioneer work of Mollema and Antonellini [2016].…”

“…With the development of ever more efficient remote sensing systems, satellite observation will soon provide regular monitoring of temporal fluctuations of open continental water surfaces with unprecedented precision. Despite their small size, gravel pit lakes are a good candidate for future monitoring by the SWOT (Surface Water and Ocean Topography) satellite [Ottlé et al, 2020]. For landscapes where few in situ groundwater level measurements are available, gravel pit lakes could be used as proxy indicators of local water resource trends.…”