Groundwater, under the right conditions can be of benefit to plants. For example, cotton can derive substantial water from groundwater at depths of around 2.6m (Wanender et al 1979). Excessive exposure to groundwater however can be detrimental. It has been shown that yield can be reduced by as much as 60% in the presence of a ground water that rises from around 3 in to less than 1m (Kahlown and Azam 2002). This occurs by either a) extending the period for which the crop root zone is saturated after irrigation or b) soil remains permanently saturated in the root zone. The depth to groundwater is primarily a function of the environmental and geological setting in which the area is located. However land management practices also have varying degrees of influence on groundwater depth.