Why can high levels of silt in irrigation water cause problems for reservoirs?

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Large wheeled irrigation sprinkler sprays water over green crops in a field, with mountains and cloudy sky in the background. — Irrigation Specialized irrigation equipment watering crops in a field.

High levels of silt in irrigation water pose a significant threat to reservoirs because they lead to a process known as siltation. When water from a river enters a reservoir, the flow velocity decreases, causing suspended sediment to settle and accumulate at the bottom.1

This accumulation creates several critical issues:

Reduced Capacity: Siltation occupies the space intended for water storage, which rapidly diminishes the reservoir's total storage capacity.1
Shortened Lifespan: By depleting storage volume, sedimentation severely limits the useful life of a reservoir. At current rates, the life expectancy of most reservoirs is less than 100 years.1
Economic and Practical Challenges: Because removing deposited sediment is generally too costly to be practical, engineers must often plan for extra storage capacity from the outset to offset these losses.1

Ultimately, streams that transport high volumes of suspended sediment are considered poor sites for reservoir construction due to these inevitable impacts on long-term functionality.1