Desktop Calendar for May 18 : 1 post by 1 author.

May – 2018

Dear Nature Lovers,

Greetings from oikos !

On its course, a river takes with it various sediments and, along the way, sculpts them into various shapes and sizes. The shapes change between the source region and the place where it amalgamates with the sea. The river’s bed and banks are continually eroded, and this adds the material (or load) to the water, which it transports downstream.

The type and quantity of the sediment load depends upon the river’s velocity , gradient rock type and the intensity of rainfall. Boulders, gravel and sand is dragged, rolled and bounced along the bottom of the river. This is called the bed load. Finer sand and mud that is supported by the water column is called the suspended load. Dissolved minerals and nutrients form soluble load which is an invisible load but matters a lot for life.

Fast moving sections of a river can carry a lot of sediment as bed load and suspended load. However, slower sections of rivers can’t, so the heavier ones are dropped first, followed by gravel and then sand and then silt. This is the reason why we see big boulders at source, coarser sediments like cobbles, gravels and sand in the plains, and sand and silt particles near the mouth of the river.

Each type of sediment forms a unique habitat in the river channel. This gives rise to a diverse flora and fauna like algae, diatoms, higher plants, insects, fishes and others. An abundance of decaying matter at the river bottom promotes the growth of plankton populations, which thrive well because of the diverse sediments. It is therefore necessary to preserve the sediment diversity within a river channel. The way we use it’s catchment affects the maintenance of this sediment diversity.

The physical and biological elements together make up a river ecosystem. Disturbing any of them changes the river’s functioning and the ecological services which mankind relies on.

Regards,
Ketaki & Manasi.
With Team oikos !

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