Table A4.4 Hydraulic load waterlogging: control points, preventive measures, target — criteria and verification Target Control points Preventive measures criteria Verification ensure it is Irrigation Irrigation tools minimised. When irrigating, apply appropriate volumes of water and use alternative Appropriate volumes of water are irrigation methods (eg drippers) to applied for plants grown, weather restrict rates of water addition. conditions, soils and the leaching fraction required. Calculated Irrigation Irrigation tools amount of water needed is Ensure irrigation scheduling methods recorded, measured on follow best practice. Water applied is application and documented. carefully calculated to match current Drainage No symptoms of waterlogging in demand, according to standard capacity of plants. Symptoms include protocols (eg see Allen et al 1998; specific site yellowing or decay between the Christen et al 2006). appropriate veins, leaf tissue becomes soft at the base or in the centre. Wilting may occur due to root decay and damaged roots blackened. Groundwater Hydraulic conductivity of the soil below 2 m profiles will cope with the required leaching fraction and irrigation volume required for the Soils Site selection plants to be grown (saturated Select sites with sufficient drainage hydraulic conductivity (Ksat) at capacity. If there is a shallow A soil Groundwater least >5 mm/hour). horizon above a layer of below 2 m Groundwater remains below 2 m impermeable clay, this may lead to during irrigation and rain events waterlogging. Drainage throughout the year. greater than Soils Site selection 5 mm/hour Verify watertable is >2 m from soil surface or the lateral hydraulic Soil water Verify watertable in piezometer conductivity of the watertable will content is >2 m from surface. handle required leaching fractions remains and irrigation rates. less than Groundwater Monitoring Soil water content less than field field capacity, drainage at least Ensure watertable remains >2 m capacity, >5 mm/hour. from soil surface. except Soils Drainage where Subsoil drainage can be installed to leaching is increase infiltration rate and remove required. If excess water. leaching Delivery of correct water volumes r Delivery of correct water volumes u Note: All control points, preventive measures, target criteria, critical limits, critical control points and their verification are site and scheme specific. The examples given in this table should be validated and verified for specific schemes. A4.3.3 Watertable rise and secondary salinity Secondary salinity is normally accompanied by waterlogging, and the relative impacts of the two
Table A4.4 Hydraulic load — waterlogging: control points, preventive measures, target criteria and verification Control points Preventive measures Target criteria Verification Irrigation Irrigation tools When irrigating, apply appropriate volumes of water and use alternative irrigation methods (eg drippers) to restrict rates of water addition. Irrigation Irrigation tools Ensure irrigation scheduling methods follow best practice. Water applied is carefully calculated to match current demand, according to standard protocols (eg see Allen et al 1998; Christen et al 2006). Soils Site selection Select sites with sufficient drainage capacity. If there is a shallow A soil horizon above a layer of impermeable clay, this may lead to waterlogging. Soils Site selection Verify watertable is >2 m from soil surface or the lateral hydraulic conductivity of the watertable will handle required leaching fractions and irrigation rates. Groundwater Monitoring Ensure watertable remains >2 m from soil surface. Soils Drainage Subsoil drainage can be installed to increase infiltration rate and remove excess water. Delivery of correct water volumes Delivery of correct water volumes Drainage capacity of specific site appropriate Groundwater below 2 m Groundwater below 2 m Drainage greater than 5 mm/hour Soil water content remains less than field capacity, except where leaching is required. If leaching ensure it is minimised. Appropriate volumes of water are applied for plants grown, weather conditions, soils and the leaching fraction required. Calculated amount of water needed is recorded, measured on application and documented. No symptoms of waterlogging in plants. Symptoms include yellowing or decay between the veins, leaf tissue becomes soft at the base or in the centre. Wilting may occur due to root decay and damaged roots blackened. Hydraulic conductivity of the soil profiles will cope with the required leaching fraction and irrigation volume required for the plants to be grown (saturated hydraulic conductivity (Ksat) at least >5 mm/hour). Groundwater remains below 2 m during irrigation and rain events throughout the year. Verify watertable in piezometer is >2 m from surface. Soil water content less than field capacity, drainage at least >5 mm/hour. Note: All control points, preventive measures, target criteria, critical limits, critical control points and their verification are site and scheme specific. The examples given in this table should be validated and verified for specific schemes. A4.3.3 Watertable rise and secondary salinity Secondary salinity is normally accompanied by waterlogging, and the relative impacts of the two u r
water-recycling-guidelines-full-21.docx