(a) Significant monotonic trend in % per year (seasonal Kendal test, p < 0.05) of SPM. Non-significant areas are represented in white. (b) Time series of averaged SPM values as a function of year during low (red dots) and high (black dots) river flow conditions. These values are extracted over the region in front of the delta (the prodelta region) where significant trends are observed to examine the origin of the trend observed in panel a (in blue in panel a). The linear regression equation are indicated for each sub-data set. Dashed lines represent the 95% confidence interval.