Richard Cresswell

Richard Cresswell

Richard Cresswell, Australia.

Richard is Water Discipline Lead at Eco Logical Australia and a Principal Hydrogeologist, with particular expertise in hydrodynamics, geochemistry and isotopes. He has over 30 years research experience across a range of disciplines, including geology, archaeology, meteoritics, geomorphology and biomedicine and has spent the last 15 years dedicated to water resources. He has authored over 40 science journal articles and 20 scientific book chapters and has presented numerous national and international papers on salinity, water resources planning, water resource assessment, groundwater research, hydro-geophysics, surface water-groundwater interactions (including on groundwater-dependent ecosystems) and water in the mining and coal seam gas industries.Richard is a member of the International Association of Hydrogeologists, The Australian Water Association and the Australian Institute of Mining and Metallurgy. He is a Fellow of the Peter Cullen Trust.

Presentation Title:Integrated agricultural and water modelling to guide Healthy Rivers in New Zealand.

New Zealand has adopted the Healthy Rivers approach to environmental restoration and control landuse change with an intent to steer waterways towards pristine conditions that provide social, economic and environmental returns. Nutrients, in particular, have been increasing at all monitoring sites for many decades, reflecting on-going land-use change, specifically the varying fortunes of the dairy industry. Highly transmissive volcanic soils result in seasonal surges in nitrogen and phosphorous loads in baseflow to creeks and rivers, with dairy farms leaching more than 50 kg/ha/a nitrate, compared to 2-5 kg/ha/a from forests and plantations. This nitrate derives from excessive fertiliser use (>250 kg/ha/a) and high returns from animal excreta. Whilst management practices have significantly improved over the last few decades, reducing leaching by half through efficient fertiliser use and judicial stock management, significant nitrates still permeate the soils and drain to rivers and creeks, resulting in algal blooms, pollution of water supplies and disruption of ecosystems. The potential exists, however, to further attenuate nitrogen levels through microbial metabolism of facultative anaerobes (primarily Pseudomonas denitrificans) in oxygen-poor groundwaters. These bacteria use nitrate as an electron receptor during denitrification and can rapidly reduce nitrate to negligible levels in baseflow to creeks. Rates of denitrification, however, are highly variable, dependent on the oxygen levels in groundwaters and rates of transport through the aquifer. Multiple lines of evidence are required to evaluate the efficacy of denitrification impacts at any given site. We have use a combination of agricultural (APSIM) and groundwater (MODFLOW_MT3DMS) modelling and local monitoring to elucidate the nitrate story across the Upper Waikato catchments of New Zealand and we use this to help dairy farmers spatially and temporally manage land use change and develop stock management strategies that incorporate denitrification as a principle component of nutrient discharge mitigation.

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