Environmental Assessment
Volume B-3.8
Mine
Hydrology
Ambatovy Project
107
January 2006
Mangoro River Pipeline
The Mangoro River will be the primary supply for mine water requirements. In
the wet season, withdrawals from the Mangoro River may be significantly
reduced if mine water requirements can be largely satisfied by excess local (mine
site) runoff. As shown in Table 3.8-12, mine water requirements of
approximately 1,000 m
3
/h (0.28 m
3
/s) represent less than 0.3% of the mean
annual flow in the Mangoro River, and less than 1.5% of the flow for dry
conditions. These dry conditions are based on minimum daily flows, but can also
be used to characterize drought conditions where low flows are maintained over a
prolonged period. In terms of maximum daily flows, the mine withdrawal would
represent less than 0.1% of the available Mangoro River water.
Table 3.8.12 Change in Mangoro River Flow due to Mine Water Withdrawal
Flow
Mangoro River Flow
(m
3
/s)
Withdrawal for Mine Supply
(m
3
/s)
Withdrawal
Driest month (Oct)
22.5
0.28
1.2%
Annual
88.9
0.28
0.3%
Minimum daily flow: 2-yr
23.3
0.28
1.2%
Minimum daily flow: 5-yr
21.3
0.28
1.3%
Minimum daily flow: 10-yr
20.2
0.28
1.4%
Maximum daily flow: 2-yr
440
0.28
<0.1%
Maximum daily flow: 5-yr
810
0.28
<0.1%
Maximum daily flow: 10-yr
1,210
0.28
<0.1%
The proposed Mangoro River pipeline is about 23 km long and crosses seven
small- to moderate-sized streams between the river and the mine site.
Construction and operation of the pipeline corridor and associated access road
may result in local increases in runoff due to land disturbance, but these changes
are not expected to be measurable in receiving water bodies. During
construction, there may be short-term changes in flow velocities and depths
where the pipeline is buried at watercourse crossing locations. No changes
during operations or post-closure are expected.
