Sediment Transport in Reservoir

Environmental concerns in lakes and reservoirs due to anthropogenic changes has prompted a need for mathematical modeling tools that can be used as a decision support system for watershed management issues. In order to get a better understanding of flow circulations, the interactions between flow and bottom and the sediment distribution, the hydrodynamic modeling is absolutely required. Here is a summary of an example numerical simulation of reservoir hydrodynamics, the sediment-transport process and its distribution.

The upper Brantas River
The 2002 and 2003 survey provided 17 cross-sections along the upper part of Brantas River and 32 cross-sections along Lesti River. The reaches are 3,645 m 7,746 m from dam axis for Brantas River and Lesti river respectively.


Sediment Transport
By employing GIS-techniques, changes of reservoir volume and bathymetry are determined. The portion of results is given in the below figures.



Compared to the observed data, they seem to be good enough.
Year 2002, the difference = 4.925.454,618 m3 – 4.527.583.411 m3 (observed)
= 397.871,207m3 ~ 8.8% of error
and
year 2003, the difference = 3.698.383,96 m3 – 3,663,658 m3 (observed)
= 34.725,64 m3 ~ 0,95% of error.



NUMERICAL MODELING
1. Grid generation - DEM ( derived from 1:25.000 map)

2. Hydrology Data



Example run #1.
Assuming the reservoir is almost empty in this stage, only 0.1m in depth of water playing as initial condition. The spillway on Dam maintains the water depth of the reservoir at 0.65m. The boundaries are set as a constant water depth in Brantas River at 0.10m and a flood in Lesti River. The flood is rising up to 1.65 m within 1200s and slowly decreasing to 0.25 at 7200s. Total computational time is 10800s.

(click here for an animation with 360s in interval).

be continued with sediment transport modules ...