Aqualinc (New Zealand)

The 2016 Mw7.8 Kaikōura earthquake induced groundwater level changes throughout New Zealand. Water level changes were recorded at 433 sites in compositionally diverse, young, shallow aquifers, at distances of between 4 and 850 km from the earthquake epicentre. Water level changes are inconsistent with static stress changes but do correlate with peak ground acceleration (PGA). At PGAs exceeding ~2 m/s2, water level changes were predominantly persistent increases. At lower PGAs, there were approximately equal numbers of persistent water level increases and decreases. Shear-induced consolidation is interpreted to be the predominant mechanism causing groundwater changes at accelerations exceeding ~2 m/s2, whereas permeability enhancement is interpreted to predominate at lower levels of ground acceleration. Water level changes occur more frequently north of the epicentre, as a result of the fault’s northward rupture and resulting directivity effects. Local hydrogeological conditions also contributed to the observed responses, with larger water level changes occurring in deeper wells and in well-consolidated rocks at equivalent PGA levels.

Abstract To support irrigation efficiency improvement, it is essential to identify the major limitations to irrigation management. Thirty‐two dairy farmers in Canterbury, New Zealand, were interviewed in order to understand current irrigation strategies on pastoral farms, particularly in relation to grazing rotations and plant available water (PAW). A water balance model, IrriCalc, was used to estimate irrigation and drainage from irrigation strategies obtained from the survey.Current irrigation strategies differ greatly from farm to farm, which depend solely on PAW with no consideration for grazing rotations. During shoulder seasons (Sept–Oct and Mar–Apr) the majority of farmers start irrigation at 50% PAW and stop at 80% PAW. During the peak irrigation season (Nov–Feb) irrigation mostly starts at 70% PAW and stops at 100% PAW, leaving no room for precipitation. Results showed that over 14 irrigation seasons (2001/2002–2014/2015) this irrigation strategy would have produced a range of drainage per irrigation season between 40 and 400 mm, which demonstrates a high potential of optimising current irrigation strategies. Better utilization of rainfall during the irrigation season would minimize irrigation requirements and drainage losses. This would help to address the issues of nutrient losses and relieve the pressure on water resources. © 2018 John Wiley & Sons, Ltd.

ABSTRACTWater use demand has increased steadily in Canterbury, New Zealand, over the last 20 years resulting in insufficient water availability. Prevailing irrigation management strategies in Canterbury consider soil moisture measurement up to a certain extent with no regard to crop’s development stages and sensitivity to water shortage; therefore, lacking to address the spatial and temporal variability of crop’s irrigation demand. This paper proposes an agent-based model that can be used to prioritise irrigation allocation to different crops on a farm. The proposed agent-based model takes into account the crop’s drought sensitivity, growth stage, soil type and the crop coefficient value when allocating water. It prioritises the crops based on their water requirements and generates an irrigation plan based on the predetermined water reduction. Our preliminary results showed that using this agent-based model, a significant water saving can be achieved even when water reduction is in effect, without impacting on production.

Transport through the soil and vadose zone to groundwater of Escherichia coli, fecal coliforms, and Campylobacter spp. from pasturing of dairy cows was studied on two working dairy farms under a traveling irrigator and a center pivot system. Leachate was collected from 1.5 m depth using a large linear lysimeter over a period of 4 yr after rainfall or irrigation applied using a traveling irrigator. There was little transport of fecal coliforms or Campylobacter from irrigation applications of 55 mm. There was some transport of fecal coliforms at applications of 80 mm (corresponding to irrigation plus heavy rainfall) but no detectable Campylobacter. When fresh cow pats were placed on half of the lysimeter plots with an 80-mm water application, there was transport of fecal coliforms and Campylobacter, but levels of Campylobacter were low (<or=4 MPN L(-1)). Groundwater at the farm with center pivot spray irrigation was monitored monthly from September 2001 to June 2007, with 60% of samples being collected from downgradient wells. Escherichia coli were detected in 5.4 and 2.8% of samples from upgradient and downgradient wells, respectively, at concentrations of >or=1 cfu 100 mL(-1). Campylobacter was detected in 0.7% of samples over the study period, with equal percentages from up- and downgradient wells. The results indicate minimal impact of dairying at these sites on microbial quality of groundwater as a result of spray irrigation using traveling irrigators at rates of approximately 55 mm every 2 wk or center pivot irrigators at 18 mm every 3 to 4 d.