Salinity Management in the World’s Most Saline Dam Reservoir: The
Gotvand Reservoir, Iran
Abstract
The Gotvand dam was built on the most important Iranian river to support
a number of populated cities with freshwater, provide irrigation water
for million hectares of fertile farmlands, and meet water demand for the
country’s hub industrial zones. This dam is known as one of the worst
engineering failures in Iran’s history because its impoundment submerged
the enormous salty unit of Gachsaran evaporite formation (GEF)
outcropped in the reservoir, leading to reservoir water salinization in
deep layers up to several times greater than that of in the high-seas.
Given the failed practical application of direct intervention strategies
to control the salinity crisis, we suggested a low-cost salinity
management strategy based on the reservoir operation to mitigate the dam
outlet salinity and preserve the downstream environment from the
salinity hazards. The three-dimensional MIKE3 model, was run to
calculate the GEF dissolution rate, accumulated salt in the reservoir,
and the dam outlet salinity. Then, we ran the model considering
different outlet salinity levels to explore the best reservoir operation
strategy to prohibit the accumulated salt in the reservoir and keep the
safe salinity for downstream irrigation-use. Simulation results
suggested that the GEF dissolution rate varied from 0.5 to 7 cm/hr,
mainly due to incremental submergence of the GEF during multi-stage
impoundment of the reservoir. Considering the final dissolution rate of
0.5 cm/hr and inlet salinity from the upstreams, salt accumulation
inside the reservoir can be gradually prevented by setting the outlet
salinity to its maximum historical downstream level, i.e., 1400
µmhos/cm.