Section 4 Part 2 - Umgeni Water

Surface Water
The hydrological characteristics of the catchments in the Mvoti region are shown in Table 4.4.
Table 4.4
Hydrological characteristics for the Mvoti region (WR90).
Annual Average
Region
River (Catchment)
Area
(km 2 )
Evaporation
(mm)
Rainfall
(mm)
Natural Runoff
(million
m 3 /annum)
Natural Runoff
(mm)
Mvoti Nonoti River (U50) 179 1 250 1 056 35.8 200
Mvoti River (U40) 3 035 1 223 892 435.0 143
Groundwater
The Mvoti region occurs in the KwaZulu-Natal Coastal Foreland Groundwater Region (Figure 4.16).
This Groundwater Region is characterised by fractured aquifers which are formed by predominantly
arenaceous rocks consisting of sandstone and diamictite that is Dwyka tillite.
Hydrogeological Units
The hydrogeologically relevant lithologies recognised in the study area comprise sandstone, tillite
and mudstone/shale supporting fractured groundwater regimes and dolerite intrusions and
granite/gneiss supporting fractured and weathered groundwater regimes.
Geohydrology
Natural groundwater discharge occurs in the form of springs, seeps and in isolated cases, uncapped
artesian boreholes. The wetlands and dams in the headwaters of the Mvoti River are supported by
perennial groundwater seeps associated with the dolerite sill intrusions in the mudstone/shale
lithologies. Springs rising in the sandstone and granite/gneiss lithologies relate to structural features
(faults and fracture zones, lineaments). An analysis of baseflow-derived stream runoff values per
quaternary catchment suggests that groundwater recharge from rainfall varies in the range 3% to 7%
of the mean annual precipitation.
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