RainfallNZ
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4 years ago Point Source Scenario details.
Implementing the Point Source Scenario required using new point source data provided by Ton. These data included a new point source site for the 2017 scenario: "Winstone Pulp WWTP at oxpond waste", which is associated with nzsegment 7196647. This segment has not been included in the CASM network before. This is the first scenario that requires a change in the CASM network. This scenario has a changed tributary network, and changed point source sites. There is also a point source site that has been removed: "NZ Pharmaceuticals wastewater". nzsegment 7240047. The removal of this site has no effect on the CASM network as it is not at the end of a tributary.
Additional scenarios have been requested. See email from Ton to Tim Kerr "FW: PC2 - additional scenarios" Monday 29th June at 7:25 and the attachment "20200626_Scenarios.xlsx" The scenarios are described in the spreadsheet which was prepared by Abby at Environment Southland. Additional details are included in the email exchange between Abby and Ton from 6:42pm June 29th. And then again in an email from Ton to Tim Kerr 29th June at 11:06 am) For the "Point source" scenario, Tim Cox may be able to simply update his model directly with new point source data from
Operative plan (Horizon's Scenario 4)
What if all properties met the operative plan's requirements? For non-intensive properties use MPI Cox-corrected losses. For all intensive land use the Operative Table 14.2 Year 20 values.
Operative plan with Dairy conversions (Horizon's Scenario 5)
What if, within each water management sub zone 11 % expansion of Dairy (from sheep and beef land) and the operative Table 14.2 Year 20 was adhered to? As for Scenario 4 except with landuse changes.
Overseer 2012-2013 rates (Horizon's Scenario 6)
What if loss rates continued as they were in 2012-13? For non intensive properties use MPICoxCorrected. For intensive properties use the properties 2012-13 Overseer-assessed loss rates (if it is available) otherwise use the MPI Cox-corrected.
Natural state scenario (Horizon's Scenario 7)
What if there were no anthropogenic nutrient sources? Implemented by converting all landuse to "Non-productive land (inactive)" and removing all point sources.
The native land use leach rates are taken from the MPI leach rate table and do not account for the variations implemented by Tim Cox to help the initial nutrient budget to balance. The Cox-variations on leach rate were sub-management-class based, not land use based. This means implementing the Cox-variations would lead to spatial variations in leach rates that cannot be attributed to spatial variations in soil, climate or slope. The imprecision of the native scenario (through not considering e.g. change in soil depths, river flows and wetlands) makes this scenario highly uncertain and only really indicative.
Federated Farmers Scenario (Horizon's Scenario 8a and b)
What if non-compliant farms were able to reduce their nutrient losses to 90 % of their 2012-23 values, or to the 75th percentile of all the 2012-13 values for the water management zone?
This is an attempt to model an approach suggested by Federated Farmers see pages 33 and 50 of their submission. Further clarification of the desired scenario was provided by email from Craig Depree (Dairy NZ) and Abbie Matthews (Horizons) dated 28th August with subject "dairy scenario" and forwarded to Ton Snelder, then to Tim Kerr and Tim Cox on the same day. See the very end of the email for the scenario specification.
Non-intensive land is left at the MPI-Cox-Corrected values. Consented land continue with their consented values. Non-consented intensive land use has its N-loss reduced to the greater of:
To be clear, the Water Management Zone baseline data, not the Water Management SUB-zone data has been used to determine the 75th percentiles. Properties without Overseer data are set to PC2 Table 13.2 Year 20.
For variant (b), as per above but in addition:
determine the average leach rate in each water management zone for the unconsented properties that have "Overseer" leach rate estimates. Apply this to all the unconsented dairy areas in a water management zone without "Overseer" estimates.
This generalises the suggested discretionary pathway, at least for the water management zones where "Overseer" values exist.
Potato Scenario (Horizon's Scenario 9)
What if potatoes were grown wherever they could be?
Ton is investigating this with help from Potato NZ (Nic Conland and Chris Keenan). See email from Ton to Chris and Nic titled "representation of more potato growing in scenario modelling" of 1st July 2020 at 12:57 pm, cc'd to Tim Kerr All LUC 1:3 land use is converted to potato growing on a 1 in 5 year crop rotation. The potato N-loss rates determined by Bloomer et al, 2020 report (Section 10) at 46 kg/ha/year. Implementation of this is achieved in two different ways:
adjusting the leach rate at all LUC 1-3 locations to equal:
46 0.2 + Existing 0.8
That is, implement a time-weighted leach rate, where 1/5th of the time there are potato leach rates, and 4/5ths of the time it is the existing leach rate.
adjusting the leach rate at all Dairy LUC 1-3 locations as in 1 above.
On 22 nd July, Nic Conland sent Ton a power point document with some alternative potatoe leach rates of 24, 13 and 9 kg/ha for "Bloomer" "good management practice" and "best management practice". The "Bloomer" rate does not match that in the Bloomer et al (2020) report so clarification is still required about these numbers.
_Bloomer, D., O'Brien, G., Posthuma, L. 2020. Modelled Loss Of Nutrients From Vegetable Growing Scenarios In Horowhenua - OverseerFM 6.3.2 Modelling of Representative Rotations within Hokio_1a, Hokio_1b, and Ohau1b WMSZ. Report by Page Bloomer Associates for Pattle Delamore Partners. Hastings.
Consents limited to PC2 Table 14.2 Year 20 (Horizon's Scenario 10)
Non-intensive land is at the MPICoxCorrected values Consented intensive land is at the lesser of the consented rate or the Plan Change 2 Table 14.2 Year 20 rate All other intensive land is at the Plan Change 2 Table 14.2 Year 20 rate
Point Source Scenario (bonus scenario offered by Ton)
Replace the point source data (which is from 2012) with 2017 data. Ton has provided this in a spreadsheet "pointSourcesTN_2012And2017.xlsx" (also in the projects sharepoint"Data" directory) that Ton provided (see email Ton to Tim Kerr) . Tim Cox may be able to implement this directly without any preprocessing.
Consent Impact Scenario (bonus last minute scenario)
What impact has consenting had on water quality?
This scenario explores how the water quality has changed by requiring consenting. Default to Cox-calibrated leach rates everywhere. For consented farms, set the leach rate to the consented value. For the unconsented farms with Overseer estimates from 2012-13, use those rates.
This scenario is intended to be compared with Scenario 6. The hypothesis is that there is an improvement in water quality resulting from consenting.
Horticulture at alternative loss rates (Scenario 13 A and B)
Original version, later called the A variant: This scenario adjusts the horticulture leach rate in the south west climate region from 71 kg/ha/year to 46. 46 is the lower rate from the "Bloomer" report for vegetables.
B Variant: As above but change to ?? kg/ha/year. This is derived from an WSP modelling referenced in section 3 of the Resumed Joint Witness Statement of the Farming and Growing Management Practices from 12th August 2020. This found that under good management practices, mixed crop vegetable rotations led to N-loss reduction of 36 to 94 %. The 36 % reduction was used as it is the more conservative option.
These scenarios were implemented by reclassifying the Cox-calibrated Leachrate raster. The leach rate of 71 kg/ha/year is unique to the SW climate region for vegies. After converting all 71's to the new vegie loss rate and the normal processing was applied. The re-calssifying was done using a function called "LeachRateReclassifier"
Proposed year 20 (pathways A and D) -Scenario 14
This scenario was requested by Christine Foster, Planing Consultant to Horizons. See email from Christine to Abby and Ton of 14th August 2020 subject "PC2 Water Quality Modelling Scenarios" and forwarded on to Tim Kerr and Tim Cox on Saturday 15th August 2020.
Consented Dairy plus all other dairy reduced by 9 kg.ha.year (down to the PC2Table 14.2 year 20 values) plus horticulture at some reduced rates assuming implementation of good management practices. Christine initially assumed the vegetable N-loss reductionw were t be agreed within the resumed joint witness statement of Experts Farming and Growing Management Practices 12th August 2020. This joint witness statement has been provided directly from Christine (see email from Christine to Ton and Abby 17th August 2020, subject "PC2 - Resumed Farm Systems Modelling". (Note that the resumed joint witness statement will eventually be made available from the Horizon's website).
As discussed in Christine's 17th August email, the joint witness statement does NOT agree on commercial vegetable growing N-loss reductions. The nutrient losses for commercial vegetable growing are discussed under issue 3 of the joint witness statement: While no agreement was reached on specified Nitrogen reductions, the statement describes WSP modeling N-loss reduction for commercial vegetable growing. This found that from a 2014 baseline without any good management practice implementation, the N-loss may be reduced by:
This scenario is to include a variant, where the unconsented dairy farms are reduced by 18 kg/ha/year. The unconsented dairy farms included in the Horizons spreadsheet are to be included explicitly.
These scenarios are to be compared with the: