The Rotten Calder Water in South Lanarkshire, Scotland, is a river that starts its journey as the Calder Water up in the Ardochrig hills above the village of Auldhouse before passing East Kilbride and Blantyre.

It continues until it meets up with the Rotten Burn, where it becomes known as the Rotten Calder Water.

The term “Water” in this context suggests bigger than a burn but not as large as a river, like the River Clyde into which the Rotten Calder eventually flows.

The Rotten Calder is a lovely river to walk beside, but its name would suggest otherwise. Rotten gives the impression that the river is in some way polluted.

But, the presence of birds such as Dippers and Grey Wagtails indicates that the water quality is relatively good as the invertebrates these birds rely on for food need clean water.

So pollution is not the reason for this river’s unfortunate name.

One theory is that the name Rotten could have come from the Gaelic word Rua, which translates as a reddish brown russet color. Over time, this has translated into the description of Rotten.

On closer inspection, the color of the river does seem to be a reddish-brown color.
So what is responsible for this color?

It is likely to be a combination of peaty soil and rock type.

Each burn emerges from mires and raised bogs, while the river itself flows through a rocky gorge where there is the presence of ironstone.

On a rainy day, if you look at where waterfalls cascade off the rocks, there is a distinct orange color that indicates ironstone.

So, in conclusion, ironstone combined with the peat that the river flows through gives the river its rusty color.

So now what about the word Calder?

Where does that term originate?

Looking at maps reveals the word Calder is used, not just in Scotland, suggesting that it is not specifically Scottish.
So after much research, I discovered one explanation that seems to make sense. Calder appears to have its roots in very early Brittonic times and means “hard” or “violent.”

When it has been raining for a long time, the surge in water can be powerful enough to carry tree trunks causing damage to bridges and paths.

But is Rusty Coloured Violent water a fitting description for the Rotten Calder Water?

Violent would only describe the river after an exceptional amount of persistent, heavy rain, which would only occur once or twice a year.

In my view, dramatic would be a better word.

It reflects more accurately the condition of the river after there has been some rain when you can hear gurgling and water cading off the rocks.

For me, that is when the river is at its best. It is then that I would recommend that you go for a walk along the Rusty Coloured Dramatic Water.