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|Title:||Long and short roads to riparian zone restoration: nitrate removal efficiency|
|Authors:||Downes, M. T.|
Schipper, L. A.
|Citation:||Conference Name: Buffer Zones: Their Processes and Potential in Water Protection|
|Abstract:||Many riparian zones have been modified or destroyed by anthropogenic practices and there is a need to develop techniques which restore their ability to protect surface water quality. Because of the multiple functions of riparian zones, there needs to be a clear understanding of the objectives of restoration and of the mechanisms by which riparian zones function. In this context, we discuss three approaches we have taken in riparian restoration which differ in their objectives and timescale of restoration. Nitrate was used as the indicator of water quality changes. In the first two approaches, two types of grazed pasture streams were fenced off to protect stream banks from stock damage: 1) Streams with a strong, spring-fed source in which riparian vegetation modified the water quality in the stream channel; 2) Streams fed by surface flows from lateral groundwater in which riparian vegetation modified the water before it reached the stream channel. In stream type 1, water quality was improved in the first few years by nutrient uptake by non-woody instream vegetation. This declined with time as woody plants developed. In stream type 2, nutrient uptake was microbially mediated along the edges of the channel. The third approach considered a stream receiving sub-surface flow from lateral groundwater. In this case a trench was dug, a metre deep into groundwater and parallel to the stream. The excavated soil was mixed with sawdust (30% v/v) and returned into the trench. Sawdust provided a carbon source for groundwater nitrate removal by denitrification. Denitrifying enzyme activity in the trench increased at least 10-fold. These studies have demonstrated a range of timescales for restoration. Riparian restoration from pasture to a cover dominated by native vegetation (as opposed to introduced pasture plants) takes about 30 years. However, the third approach shows that modifying the path of groundwater flow has the potential to quickly decrease groundwater inputs of nitrate to surface waters within a matter of months.|
|Place:||London, United Kingdom|
|ISBN:||0 9530051 0 0|
|Appears in Collections:||Hunter Local Land Services|
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