The use of riparian buffer zones for the attenuation of nitrate in agricultural landscapes.
The focus of this mini-dissertation is the use of riparian buffer zones to manage nitrate pollution of water resources. Riparian buffer zones are vegetated areas adjacent to streams, lakes and rivers, that are managed to enhance and protect aquatic resources from the adverse impacts of agricultural practices. These zones are recognised globally for their function in water quality amelioration. Despite the growing literature, there is little consensus on how to design, assess and manage these riparian buffer zones specifically for nitrate attenuation. For the purpose of this mini-dissertation, a literature review of world-wide research into the nitrate attenuation efficiencies of riparian buffer zones was undertaken. A database was created using the key information from this literature. Two key processes responsible for immobilising and/or removing nitrate from surface and subsurface flows are generally recognised in the available literature, namely: vegetative uptake and the process of denitrification. A comparison of the available riparian studies indicated that there are similar characteristics in riparian buffer zones that may be responsible for enhancing these key mechanisms. Studies where there was shallow lateral subsurface or uniform surface water delivery pathways, vegetation of close structure and composition, high organic matter in the soils and fluctuating soil surface saturation rates showed the most significant nitrate attenuation efficiencies. The mini-dissertation proposes that these similarities can be used to both assess a riparian landscape for its potential to attenuate nitrate, and to size a riparian buffer zone specifically to meet this function. A set of proposed guidelines based on the findings of the dissertation attempt to illustrate how riparian pollution control recommendations can be achieved. These guidelines are an example of how to assist a farmer or similar landowner in achieving good nitrate removal efficiencies from a riparian buffer zone. The guidelines work through three steps, which help to establish and prioritise management zones, assess each zone's potential for nitrate attenuation, and determine adequate riparian buffer widths for each management zone. A case study was used to illustrate the practical application of the guidelines. Full testing of these guidelines was not within the scope of this mini-dissertation, however the guidelines are an indication of how information regarding riparian function can be applied to a system to determine effective management of water resources.