## 2 Materials and Methods
### LUIPLES Method for the Assessment of Pollution-Related Pressure Levels  
For the quantification of pollution pressures, the method developed, LUIPLES (Land Uses for estimating Pressure Levels to approach the Ecological Status), is based on the quantification of the relative influence of land uses on the four main pressures related to  
Figure 1: Map of the location of the waterbodies where land uses in the catchments were determined for pollution pressure estimation; all located within the European Mediterranean biogeographical region. The sites tested for hydro-morphological pressures are listed in Table S1. pollution experienced by lentiic ecosystems, namely: eutrophication, organic enrichment, acidification, and pollutant pressures. Land uses were aggregated into groups from the different land cover uses that appear disaggregated at the third level category of CLC. Groups of land use of a similar type and incidence on each specific pressure were joined (Figure 3b). The groups were:  
* Irrigated agriculture areas, such as rice fields, vegetables and fruit trees (CLC codes 212, 213 and 222). * Rain-fed agriculture, including vineyards, olive groves, annual crops associated with permanent crops, mosaic crops, agricultural lands with significant natural and semi-natural vegetation spaces, as well as agroforestry systems (CLC codes 211, 221, 223, 241, 242, 243, 244). * Pressures exerted by livestock were estimated from land uses such as meadows and natural pastures (CLC codes 231 and 321). * Urban uses by continuous and discontinuous urban structure, industrial and commercial areas, railways and associated land for these networks, port areas, airports, areas under construction, green urban areas, and sports and leisure facilities, which correspond to the CLC codes 111, 112, 121, 123, 124, 133, 141, 142, respectively. * Finally, communication infrastructures (code 122), dumps (code 131), and mining areas (code 132) were also each mapped and assessed separately. Natural uses were not considered for the pressure assessment due to their low impact regarding the pressures identified in comparison with the other land uses promoted by the human activities. Figure 2: Steps followed for the delineation of the catchment area of the 11 studied coastal logoons in Geographic Resources Analysis Support System (GRASS) Q-GIS, with the example of CANE (Etangs de Canet et de Villeneuve-de-la-Raho waterbody): (**a**) Digital Elevation Model (DEM) and coastal lagoon delineation; (**b**) flow accumulation map; (**c**) drainage direction map; (**d**) streams map; (**e**) sub-catchments map (minimum 2000 pixels per sub-catchments); (**f**) integration of sub-catchments and total catchment (in black). Figure 3: (a) Land uses obtained from Corine-Land Cover (CLC) in the catchment area of CANE (Etangs de Canet et de Villeneuve-de-la-Raho waterbody) (taken as an example). (b) Land uses joined by the land use groups established for the LUPLES (Land Uses for estimating Pressure Levels to approach the Ecological Status) method. Dumps and mining do not appear because their coverage is not relevant in the catchment of this lagoon. In order to normalize the data for their use as pressure estimations, the percentage of the area occupied by each of these land use groups regarding the total catchment is used, as follows (Equation (1)):  
\[\text{Land use pressure level = [(Land use group area, km}^{2})/(\text{Total catchment area, km}^{2})]\cdot 100 \tag{1}\]  
Once the data for the areas of each land use type had been normalized, the relative contribution of each land use type to the level of each specific pressure related to pollution (autrophication, organic enrichment, acidification and specific pollutants) was obtained for each of the studied coastal lagoons by using a weighting factor. Weighting factors were adjusted according to the relative influence of each land use on each defined pressure type, the later causing impacts on the waterbody.