Environmental Engineering Reference
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Fig. 16.18
The multi-arched Churchill Dam on the Kromme River in the Eastern Cape of South
Africa
up to eight, further treatments before a given invasion is reduced to acceptable
levels (McConnachie et al. 2012 ) (Table 16.3 ).
Thus Working for Water is clearing aliens at three times the rate of invasion.
16.4 Discussion
Over the past half century wetlands, floodplains and fertile riverbeds, the areas in
the catchment that are the most vital in terms of providing essential services to
mankind, have been the most heavily impacted and transformed. Research has
shown the transition from intact indigenous vegetation to landscapes heavily
transformed by agriculture and invasive alien plants results in significant hydro-
logical changes (Prinsloo and Scott 1999 ; Jackson et al. 2001 ; Jewit 2002 ; Gleick
2003 ; Shiklomanov and Rodda 2003 ; Allan 2004 ; Scanlon et al. 2007 ; Gleick et al.
2011 ). The main drivers of land-use change and wetland transformation in the
Kromme appear to be unsustainable agricultural practices and alien invasion of the
riparian zone. These drivers cause erosion and headcuts, lowering of the water
table, decreased river flow due to increased transpiration and irrigation, greater
flood damage, decreased base flow and a decrease in water quality (Hibbert 1971 ;
 
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