A R package for quickly updating trend analysis: application to French streamflow time series.

This work presents trend analyses performed on time series. It follows the work done by Giuntoli et al. (2013) on trend analysis of low flows and their relationship with large-scale climate variability in France. A R package was implemented to allow the extraction of variables on time series and performing statistical trend analysis on the extracted variables. Detected trend can be summarised on maps. The methodology uses the Mann-Kendall statistical test to assess the significance of linear trend. Regional consistency can also be checked.

The methodology used was performed on 207 French daily streamflow over the period 1968-2020. Three period subsets are studied: 1968-2000, 1968-2010 and 1968-2020 to compare trend results and assess the variability over time.
Results confirm a North-South geographical split in temporal trends for droughts. They also show the increase of the severity of droughts over the last decades in Southern France.

Results also suggests a similar North-South geographical split for high and medium flows. They show that temporal trends are decreasing over the last decades in the Southern part of France for both high and medium flows. However, in the North part of France, results shows less significant trends in streamflow time series.

Giuntoli, I., Renard, B., Vidal J.-P., and Bard, A. (2013). Low flows in France and their relationship to large-scale climate indices, Journal of Hydrology, 482, 105-118, http://dx.doi.org/10.1016/j.jhydrol.2012.12.038.