How to prevent sludge deposition in reservoirs?

How to prevent sludge deposition in reservoirs?

In the case of accumulation lakes (1), especially artificial ones, a large problem is the deposition of sediments at the bottom of the accumulation lake, especially near the dam (2). Such lakes, in addition to serving for the production of hydro energy, often serve as a source of drinking water and to feed the fields.

And they are often used for recreational purposes.

Rivers naturally carry sediments such as gravel, sand, silt and clay. When water hits the dam, the water flow slows down, and sediments settle to the bottom. Over time, the amount of sediment can rise so much that it bury a large part of the lake, thus reducing the accumulation capacity of the lake.

In order to solve this problem, it is necessary to ensure constant cleaning of sludge from the bottom of the lake. This is most easily achieved by preventing the water from slowing down at the bottom. Slowing down the water at the bottom of the lake can be prevented by taking water from the bottom. To do this, it is necessary to place wide suction pipes (3) (preferably concrete) at the bottom of the tank with perforated small openings on the side through which water enters the suction pipe (3), and it is used for various purposes. The velocity of the water entering these perforated pipes is about openings large enough to draw the sediment with it. In that way, the sediment would not remain at the bottom of the lake, but would go away with the water. The width of the suction pipes (3) should be larger at the dam (1), and further towards the beginning of the lake (1) the width of the suction pipes (3) should decrease so that the water inside them would be approximately equal to the entire length of the suction pipes (3).

The width of the small side openings on the suction pipes (3) depends on the purpose of the water.

If drinking water is used on the long suction pipe (4) the openings should be very small.

And on the pipes that would serve to bring water into the water turbines (4), the openings would also have to be very small, so that coarser sand would not damage the turbine blades.

On the pipes that would be used for irrigation of the field (5) through the open channels, the openings should be several centimeters in size so that silt, sand and even small gravel could pass through them.

On the pipes that would be used for irrigation through the pipe system (6), the openings should be smaller so that no sand enters the pipe.

On the pipes that would serve for emptying the accumulation basins (7) in cases of high water level and sudden inflow of a large amount of water, the openings should be large enough for the passage of larger gravel.

All these pipes (3) should be placed parallel to the bottom of the lake (1), along the entire length of the lake, with a distance of several meters from each other in order to keep the bottom around them at the same level at all times. At a few meters from the pipe, the sediment could raise the bottom a little, but larger deposits would constantly collapse, thus preventing a significant rise in the soil of the lake.

The openings on the suction pipes (3) could become clogged over time, so they should be cleaned from time to time on the outside with a strong water jet. This cleaning job could be done by small robotic unmanned submarines with remote control.

With such a system of protection against sediment at the bottom, only larger stones and gravel could be significantly deposited, while clay and silt would mostly go to irrigation fields. This would clean the lake and fertilize the fields at the same time.

Larger stones and gravel that would remain on the upper part of the lake, after being cleaned of sludge by this procedure, could be extracted as construction material.


Other of my technical analyzes and innovations can be found in this book.