Critical Source Areas
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Critical Source Areas (CSAs) are small, low-lying parts of farms such as gullies and swales where runoff accumulates in high concentration. This page emphasises that by managing CSAs effectively, you can reduce the loss of nutrients and sediment from your farm. Steps include identifying CSAs on your farm and establishing grass buffer zones to filter contaminants. Also, divert new tile drains into areas where runoff can be filtered before entering waterways. This results in benefits such as reduced loss of topsoil, lowered nutrient and sediment loss to waterways, and improved animal health. Remember, the faster the water flows, the wider the buffer zone should be.
Critical source areas (CSAs) are small, low-lying parts of farms such as gullies and swales where runoff accumulates in high concentration. Runoff from CSAs carries sediment and nutrients to waterways. Managing these areas well is a great way to reduce sediment and nutrient loss from your farm.
Buffer zones or grass strips in and around CSAs and next to waterways act as filters by slowing overland flow to trap suspended contaminants.
The buffer zone should be left uncultivated and ungrazed to operate effectively.
The faster the water is flowing into a buffer zone, the wider the buffer zone will need to be to provide time for effective filtering. This is particularly important in a CSA or on sloping land.