Environmental Assessment
Volume E-3.8
Tailings Facility
Hydrology
Ambatovy Project
64
January 2006
3.8
SURFACE WATER HYDROLOGY
3.8.1
Introduction
Development of the tailings facility will involve the collection and diversion of
surface runoff in the upper basins of the affected watersheds. The facility will
also include a series of interceptor wells downgradient of the embankments that
will collect seepage and return it to the water pond. As a result of these
diversions, flows in the downstream valley will be reduced and the availability of
water for other users (i.e., human and animal consumption, irrigation and fish
habitat) may be affected. Long-term changes in flows and water levels could
also affect the channel morphology of receiving streams.
Regional climate and hydrologic information have been compiled to characterize
baseline conditions in the tailings area (Volume I, Appendix 8.1). The available
baseline information is used in the following sections to evaluate potential effects
of the Ambatovy Project (the project) on streamflow and sediment yield.
3.8.2
Study Areas
The tailings facility is located in the upper valley of three parallel tributaries to
the Ambolona River. As shown in Volume A, Figure 7.2-3, the hydrology local
study area (LSA) extends from the headwaters of the valleys, along the main
stem of the Ambolona River, to the confluence with the Vorinkina River about
2 km downstream of the south valley. This endpoint was chosen to enable the
assessment of combined impacts from each of the basins on the Ambolona River,
and because any impacts from the tailings facility would be greatly reduced
downstream of the confluence with the larger Vorinkina River.
3.8.3
Baseline Summary
3.8.3.1 Introduction
Baseline conditions in the tailings area were characterized by analyzing available
climate and hydrologic (streamflow) data. A summary of the climate and
hydrology baseline study is provided in the following sections. Details can be
found in Volume I, Appendix 8.1.
3.8.3.2 Methods
Information on Madagascar’s climate was primarily obtained from Chaperon et
al. (1993). Climate information was also obtained from the World
