OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

3.18.6 Implications for water quality and quantity management
There is some evidence to suggest that the Moatize Coal Mine may have had a minor-medium impact on local
water quality whilst other mining operations are likely to have had small, localized impacts at most. The artisan
gold diggings have contributed to a considerable increase in the suspended sediment load of the Zambezi River
during periods of low flow. The Matangua uranium and thorium deposit holds the risk of contaminating local
water supplies.
3.19 The Shire (Malawi) sub-catchment (including Tanzania)
3.19.1 General description
3.19.1.1 Hydrology
This area comprises one large sub-catchment containing the Lake Malawi and its outflow, the Shire River, with
a series of smaller streams and rivers that drain into Lake Malawi from the Malawi and Tanzanian portions of
the rift valley.
In the Tanzanian sector, the most import inflow is the Ruhuhu River, with smaller rivers draining the Livingstone
Mountains and entering Lake Malawi at Songwe. All of these rivers are short, with steep gradients and carry
large volumes of water since they drain areas that receive annual rainfalls in excess of 2,000 mm.
Lake Malawi also receives inflows from several smaller perennial streams and rivers that drain the Rift Valley
and flow into the lake. Outflows from Lake Malawi flow down the Shire River to the Zambezi River.
The Shire River is perennial, though flows have declined in recent years due to a drop in the water level of Lake
Malawi. The lower portion of the Lake Malawi Rift Valley lies in a partial rain shadow that reduces rainfall from
the southeasterly winds, and annual rainfalls average some 850 mm. Slightly further south, the Mulanje Plateau
receives over 2,500 mm of rainfall and provides strong inflows into the Shire River.
All of the smaller, perennial and non-perennial streams that drain the Rift Valley into Lake Malawi have steep
gradients and have incised deeply into the country rock.
3.19.1.2 Geology
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