Nitrates in water – now and inthe future
Predicting nutrient exports from catchments, and inputs to receiving lakes and estuaries, will become more accurate with the development of a new GIS-based model, ‘ROTAN’. ROTAN can model the effects of land-use changes, and mitigation measures such as tree planting along riparian margins, on nitrogen export to waterways.
Increasing nitrate concentrations in major streams draining into Lakes Rotorua and Taupo sparked the model’s development. Using ROTAN we can now provide information such as:
- maps showing the flow and nutrient delivery pathways from each part of the catchment to the lake
- tables for each part of the catchment showing quantities of flow and nutrients, time delays, and nutrient losses
- tables/graphs showing historic trends in land use, stocking rate, and fertiliser usage
- tables/graphs showing the relationship between historic trends in land use, rainfall, and stream nutrient concentration
- predictions of nutrient inputs to the lakes for various scenarios of land use, rainfall, and mitigation measures.
ROTAN is being applied in the Rotorua catchment for Environment Bay of Plenty in collaboration with GNS Science, and at Taupo as part of Foundation for Research, Science & Technology-funded research in collaboration with AgResearch, Lincoln Ventures, and GNS Science.