Environmental Assessment
Volume B-3.8
Mine
Hydrology
Ambatovy Project
94
January 2006
Actual evapotranspiration (ET) at the mine site is estimated at 750 mm per year.
Evapotranspiration rates for the Torotorofotsy Wetlands are expected to be closer
to potential ET due to near-continuous water availability and are estimated at
900 mm/year. Based on data from 2004 to 2005 monitoring period, annual
runoff for the mine, Torotorofotsy and the Mangoro areas is on the order of 500
to 800 mm.
The Mangoro River mean monthly and annual flows are shown in Table 3.8-4.
Maximum and minimum daily flows are shown in Table 3.8-5.
Table 3.8-4 Mangoro River - Mean Monthly and Annual Flows
Mean Monthly flow (m
3
/s)
River and
Location
Drainage
Area
(km
2
)
Period
of
Record Nov Dec Jan Feb Mar Apr May Jun
Jul
Aug Sep
Oct
Annual
Mangoro at
Mangoro Gare
3,600
1956-
1997
(a)
52.4 111 165 179 177 109
68
56.6 49.8 42.5 34.2 22.5
88.9
(a)
Madagascar Ministry of Public Works and Transport, Meteorology Branch 2005 (1979-1997 data).
Note: Numbers have been rounded for presentation purposes.
Table 3.8-5 Mangoro River - Extreme Daily Flow
Minimum Daily Flow,
Qmin (m
3
/s)
Maximum Daily Flow,
Qmax (m
3
/s)
River
Drainage Area
(km
2
)
Period Of Record
10
years
5
years
2
years
2
years
5
years
10
years
Mangoro at
Mangoro Gare
3,600
1956-1979
20.2
21.3
23.3
440
810 1,210
(a)
Source: Chaperon et al. 1993.
(a)
Extrapolated values.
3.8.4
Issue Scoping
Hydrology issues related to the project were identified through consultation with
stakeholders and by reviewing previous environmental assessments for resource
developments in Madagascar and elsewhere. As described in Volume A, the
issues were identified, tracked and summarized at a high level for consideration
in the impact assessment. The following hydrology issues were identified:
•
changes in flows, water levels and sediment loads that could alter
channel morphology and sediment concentrations; and
•
changes in water availability for various uses (human and animal
consumption, irrigation and aquatic habitat, including the Torotorofotsy
Wetlands).
