(a) Urbanisation and intensive agricultural operations are similar in many ways and different in others in terms of both impact on aquatic ecosystems and practices (both structural and non-structural) to mitigate these impacts. Source controls are one such practice; they take different forms at the farmstead and field levels. (b) In this paper, source controls are classified as those primarily directed at controlling runoff quantity (which also mitigate water quality impacts) and those concerned with runoff quality. As is the case in urban areas, the former generally have a longer history than the latter. This classification s somewhat artificial. For example, early practices for reducing runoff also reduced erosion and sediment in receiving waters. However, the focus on erosion was soil loss rather than quality of the receiving waters or ecosystem degradation so that the classification still applies. (c) Measures for reducing runoff and erosion, which are applied at the field level, include conservation tillage, cover cropping, and maintaining/restoring wetlands. Measures for enhancing water quality, which are applied both at the farmstead and field levels, include education, awareness and participation, process control, input and waste management, and buffer zones and shelter belts. (d) For each of the above measures, there are both general and specific guidelines, and demonstrated performance through research and demonstration projects. However, at the field level in particular, there is far more variation in acceptable measures than in the urban case. This is due primarily to the wider variation in the natural environment than in the built environment, but also to the wider variation in economic incentives/disincentives. (e) Another difference between the urban and agricultural cases, in some instances, is the proximity of the source to the upper ends of the impact 3d aquatic ecosystems and the general affinity that fanners have to the land. As a result, one might expect more receptive audience for education, awareness and participation measures.
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