Strategy for FOCUS run-off scenarios

According to the SW FOCUS report (FOCUS, 2001) each of the 4 run-off scenarios represents a defined vulnerable situation with respect to possible surface water contamination by

pesticides. The concrete characterisation of the scenarios, the FOCUS SW group explained in their report on table 3.2-6 (FOCUS, 2001), page 37). The most relevant information is summarised in table 2-18.

Table 2-18: Selection properties of the FOCUS run-off-scenarios (FOCUS, 2001).

Scenario

° soil texture class 3 (medium fine) used in the analysis for R1 and R3

^ soil texture class 1 (coarse) used in the analysis for R2 as the soil in the scenario is actual sandy

* soil texture class 2 (medium) used in the analysis for R4

In this study a similar procedure was followed to analyse the relevance of the FOCUS EU run-off scenarios for the agricultural area of Norway, considering thematic maps with information on topsoil texture, annual rainfall, annual temperature, and land cover. As the models does not consider slope for calculating the amount of runoff water, slope was not considered further here. To perform an analysis similar to the original FOCUS evaluation, also other soil parameters (e.g., parent material) were not taken into consideration.

Different tables in FOCUS (2001) shows that this report is not very strict regarding the methodology described in its chapter 3 since the soil that was picked for R2 is rather sandy (>70 %). Therefore, the soil texture class 1 (coarse) was used for R2 in this analysis.

Table 2-19: Key properties of the FOCUS surface water scenarios (FOCUS, 2001).

Scenario Corresponding STU attributes Annual rainfall^

location Soil

Date of first application March to

Medium fine. <15% sand and <35% clay. 4. Fine 35% to 50% clay

* all R1-locations with rainfall < 800 mm were considered as being dryer than FOCUS R1

** All R2 locations with annual rainfall <1000 mm were considered as being dryer than FOCUS R2

°° All R4 locations with annual rainfall < 700 mm were considered as being dryer than FOCUS R4

^ Based on the selected weather year for each application season for creation of PRZM to TOXSWA (P2T) files and the corresponding rainfall over 12 months

Comparing different tables in the FOCUS report further shows that it is also not very strict on climate data categorization. Therefore, another adjustment was done regarding the grouping of scenarios based on precipitation data. The actual annual rainfall in the selected weather years (table 2-19) used when performing FOCUS simulation (see also FOCUS 2001, table 4.1.2-3), shows that the actual weather conditions selected by FOCUS for R1 is not lower than for R3, as opposed to what is indicated in table 2-19. Therefore, the following classification was performed to compensate for these inconsistencies in the FOCUS document:

• All locations with rainfall >800 mm were considered representative for R1

• All R2 locations with annual rainfall >1000 mm were considered as being representative for FOCUS R2 (extreme worst-case selection since the actual minimum rainfall at R2 is, at least 1400 mm)

• All locations with rainfall ≤800 mm were considered representative for R3

• All locations with annual rainfall >700 mm were considered representative for R4

Figure 2-24. Flow chart describing the representativeness analysis of the FOCUS surface run-off scenarios in this study

The flowchart in figure 2-24 shows how the respective maps were combined.

The initial procedure of the analysis was to consider the two key properties texture and rainfall in the same way as FOCUS developed in 2001. Based on the map for soil texture (figure 2-18) and overlay of annual rainfall (figure 2-20), the agricultural area will contain four main groups; three run-off groups (R1/R3, R2, R4) and a group of locations which is considered as not vulnerable to run-off according to FOCUS because they have no soil texture (i.e., histosols).

It is not possible to distinguish between the scenarios R1 and R3 because they belong to the same texture class. Therefore, they are called “run-off groups” rather than “run-off

scenarios”. After overlay with annual rainfall R1 (locations with annual rainfall >800 mm) and R3 (locations with annual rainfall <800 mm), the analyses would split up and finally result in

Start map

Validated Corine land use map

Assignment 2 Subgroups with less rainfall

{R1, R2, R3, and R4}

with correct rainfall {R2 and R4} with less rainfall

No run-off-scenarios with correct temperature 4+2 run-off scenarios colder than EU-FOCUS

WorldClim annual rainfall map

mean spring/autumn temperature map JRC based on WorldClim EUsoil data base ESDB v2

Attribute: texture

four different run-off scenarios. In contrast, the representative locations for runoff scenarios R2 and R4 were already completely defined based on soil texture only. However, rainfall was used to further classify respective locations (either “rainfall according to FOCUS” or “rainfall lower than FOCUS”).

The next steps were to consider climate information on temperature to further classify into subgroups for run-off scenarios (Jones et al., 2005).

Organic matter and slope were not further considered as criteria. Organic matter was not considered because pesticides are anyhow transported during the run-off event, either via the water phase (soils with low organic matter contents) or via the suspended soil particles (soils with high organic matter content). According to the respective map presented

previously (figure 2-23), slope is a dominant factor in nearly all agricultural fields in Norway.

Therefore, also the slope was not considered further to discriminate among scenarios.

The exact analysis procedure was based on the methodology FOCUS developed in 2001. In the final step, the temperature map (figure 2-21) was used to complete the given climate properties of the run-off scenarios. Areas which do not fit with respect to the temperature are considered as variations to the main scenarios.