Reservoir seepage management design

[mmeyer]

Need to get some advice concerning a seepage management feature proposed for a large reservoir. The reservoir has a capacity of approximately 400k acre-feet at a depth of 12'. It is an aboveground reservoir surrounded by levees. The reservoir is constructed aboveground due to the highly permeable subsurface geology (pourus limestone caprock about 5'-10' below soil surface). The main purpose of the reservoir is to control storm flows by storing the water and gradually releasing it at a later date. We don't plan on placing a liner within the reservoir and expect seepage to take place. The seepage is captured in a large seepage canal located about 100m from the base of the levee. We plan on allowing the area between the levee and canal to act as a seepage buffer, allowing water to be stored in the soil and lost through evapotranspiration. We also plan on allowing the buffer area (approximately 500 acres) to vegetate with a variety of wetland species to provide some ecological benefits. Has anyone heard of this type of design or have any suggestions. Our engineers have run various models and say it is feasible and cost effective but we have some naysayers from other groups questioning this design.

 

[cvg]

Have the naysayers given any reasons for being pessimistic?

This is not totally new as I know of more than one artifical reservoir (lakes) that lose water at such a high rate that there is virtually no seepage through the dam and the spillway never operates.

 

[mmeyer]

That's the problem. They have asked our engineers to provide the modeling data, our biologists have provided the ecological data, but they have not volunteered to give us any reasons for their opinion. The only thing we can get from them is that we are losing the possibility to expand the reservoir into this buffer area. My response back on that is that even if we did expand the reservoir into this area (a 1/60th increase in total volumn) we would still need some sort of seepage buffer or control for the reservoir.