Clutha Delta

The above soil moisture plot shows the percentage of moisture in the top 200 mm of soil (Left hand axis). Soil moistures are separated into four zones: Red, Orange, Yellow and Green Zone, with the Field Capacity line at the top of the Orange Zone showing the maximum amount of water that the soil can hold, the Red ‘Saturated soils Zone’ above field capacity shows that the soil is completely saturated. Guidance for effluent irrigation application is set out below with reference to these four zones. Rainfall on a daily basis is shown on the right hand axis.

Key:

Saturated Soils: Applying effluent to saturated soils is NOT a permitted activity, and if found to be in breach of this rule, may face compliance action. The soil is so full of water that any effluent applied is likely to runoff or leach through the profile.

Field Capacity: The maximum amount of water the soil can hold is expressed as a percentage of soil volume and for this soil the field capacity is 50%. This means there is 100mls of water in the top 200mm of soil when the soil moisture is at field capacity of 50%.

Soil type: The soil type at this site comprises Waikoikoi deep silt loam (Pallic soil) on undulating terrain with a pronounced pan at 400mm to 450mm depth and is poorly drained in its natural state. This drainage pattern has been modified with mole and tile drainage which improves soil health and pasture growth. The presence of mole and tile drainage does however increase the risk of effluent bypass to waterways when soil moisture levels are high (refer to guidance section below).

Please Note:

The soil moisture graphs and corresponding information are intended as a guide only. Rainfall and soil types on your property may vary to the information shown. This soil moisture site is designed to provide guidance in deciding whether to apply effluent. All farmers must use their own judgement in determining if effluent can be applied safely on their property.

Guidance for effluent application - with a travelling irrigator

Red (Saturated soil) Zone (>50% soil moisture)
Effluent irrigation with a travelling irrigator should not occur when readings are within the Red Zone as soils are saturated. Applying effluent to saturated soils is NOT a permitted activity, if found to be doing so you may face compliance action as it is in breach of ORC rules. There is a high risk that the effluent would make its way into waterways either by overland flow or via drainage through mole/tile drains.

Orange Zone (between 42.5% - 50% soil moisture)
Effluent irrigation with a travelling irrigator should not occur when readings are within the Orange Zone as soil moisture is considered to be too close to Field Capacity. There is a high risk that the effluent would make its way into waterways either by overland flow or via drainage through mole/tile drains.

Yellow Zone (between 35% - 42.5% soil moisture)
Effluent irrigation with a travelling irrigator may commence with caution when readings are within the Yellow Zone. Irrigation needs to be carried out with care. A travelling irrigator needs to be set at maximum travelling speed as there is still a medium to high risk for effluent to enter waterways either by overland flow or via drainage through mole/tile drains.

Green Zone (<35% soil moisture)
Effluent irrigation with a travelling irrigator can operate within the Green Zone with a much reduced risk of effluent entering waterways either by overland flow or via drainage through mole/tile drains, provided best management practices for irrigating are followed and the irrigator remains set at maximum travelling speed. Be cautious with effluent application when the soil is extremely dry as effluent may move straight to tile drains via soil cracks.

Guidance for effluent application - with a low rate system

Red (Saturated soil) Zone (>50% soil moisture)
Effluent irrigation with a low rate system should not occur when readings are within the Red Zone as soils are saturated. Applying effluent to saturated soils is NOT a permitted activity, if found to be doing so you may face compliance action as it is in breach of ORC rules. There is a high risk that the effluent would make its way into waterways either by overland flow or via drainage through mole/tile drains.

Orange Zone (between 42.5% - 50% soil moisture)
Effluent irrigation using a low rate system should be delayed when readings are closer to the Field Capacity line, as there is still some risk that the effluent would make its way into waterways through mole/tile drains. Small pulsed applications of effluent may be made with caution when readings are within the orange zone.

Yellow Zone (between 35% - 42.5% soil moisture)
Effluent irrigation using a low rate system can generally be carried out within the yellow zone as there is a much reduced risk of effluent entering waterways through mole/tile drains.

Green Zone (<35% soil moisture)