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

3.37.3 Alluvial mining
Alluvial mining of gold is reported by Chiyanike (1997) from the Mazowe, Nyadiri and Nyagui Rivers (Figure
3.14). Other tributaries, such as the Mufurudzi River, are also alluvial mined. The alluvial mining is very
extensive.
3.37.4 Monitoring systems
ZINWA is currently setting up a monitoring system.
3.37.5 Water quality data
None available from ZINWA. Chenje and other (1998) provided data on discharges from Trojan Mine.
Table 3.37: Actual discharge from Trojan Mine, after Chenje et al. (1998).
PH 7.07 Alkalinity 140ppm TDS 221ppm Total
hardness
-
NO3
8.06ppm N Cl -
3-
2ppm PO4
Mg 8ppm Ca 34ppm K 4.6ppm
The most significant impacts of mining to be expected are:cci
2-
0.2ppm SO4
84ppm
13ppm
Gratwicke (1999), in a study on rivers downstream of the Mazowe Group and iron Duke Mines, provides the
following data (Table 3.38):
Table 3.38: Data from Mazowe area: range over 9 months, after Gratwicke (1999).
Site name
(Gratwicke 1999)
Mine Citrus Bridge After confluence
pH 3.10 – 6.90 6.95 – 7.94 6.29 – 7.92
Conductivity / µS/cm 125 – 5000 348 – 475 330 – 490
Dissolved O / ppm 0.00 – 6.84 5.18 – 7.52 4.10 – 7.40
Location relative to mines Below Iron Duke Below Mazowe Group Below both
3.37.6 Implications for water quality and quantity management