Raging Memories

A reader, who wishes to remain anonymous, wonders why natives in East Africa falsely remember that long ago rivers were raging torrents all year round, compared to seasonal trickles now:

Participatory research in East African catchments uncovers memories of catchment hydrology at odds with the hydrological record. Community elders paint a picture of drying and increasingly seasonal rivers; gone are the raging torrents of their youth, replaced by trickles which flow only in the rainy season. However, hydrological records from colonial and the post-independence era suggest that these memories are something of a fiction. In certain catchments, river flow has actually increased over time.

I wonder if you might be able to explain this apparent bias. It may be that participatory research methodologies are to blame – eliciting false information. However, conversation with colleagues indicates that this discrepancy between memory and the record may be a global phenomenon. Additionally, I have noticed that the conclusions of scientist colleagues appear to be influenced by community perceptions of a changing hydrology.

If there is a bias at work, do you think this may have consequences for our understanding of climate change? Do false childhood memories influence the popular  view that the weather is changing?