ERSE carries out analysis of inland waters in Tuscany and the rest of Italy, using the following synthetic indexes.

The EBI relies on the analysis of benthic macroinvertebrates communities colonizing the river ecosystems, especially on the qualitative-quantitative comparison between the sampled macrobenthic population and a generic population “expected” in free of anthropic impact habitats. Changes in the population’s composition are related to the set of effects provoked over time by different causes of disturbance (physical, chemical and biological). These changes are translated into numerical values by the Index and in turn linked to an ecological quality class.

The STAR_ICMi index (STAndardisation of River classifications_Intercalibration Common Metric index) allows to derive a quality class using macrobenthic organisms as indicator, defining the ecological status of the station in question, according to the requirements of the Water Framework Directive (WFD: 2000/60/EC). The main differences compared to other indexes based likewise on macrobenthos are: a sampling that is replicated according to the representativeness of the varied types of microhabitats present; the count of each systematic unit detected replacing the determination for presence/absence; the calculation of the index derived from six suitably weighted independent metrics.

Diatomic indexes are intended to define the ecological status of a stream based on the specific composition of benthic diatom’s population (Bacillariophyceae). These indexes are weighted on the characteristics of the individual species (such as sensitivity to pollutants, ecological plasticity, relative abundance within the population): the values obtained can be referred to Quality Classes established in advance, or to reference conditions calculated for each river macro-type, as required by Directive 2000/60/CE. The EPI-D (Eutrophication/Pollution Index-Diatom based) is the only index developed for the Italian territorial context, but it does not comply with the European water directives and cannot be used to determine the ecological quality ratio (Ecological Quality Ratio: EQR). Contrariwise, the Multimetric Intercalibration Index (ICMi) complies with the requirements of Directive 2000/60/EC. Additional diatomic indicators (such as TDI, TI, IPS, SI, IBD, IDG) may be calculated, upon agreement, based on specific customer requests.

The IBMR index is based on the analysis of the aquatic macrophyte community to evaluate the trophic state of watercourses. The use of macrophytes as indicators of the quality of flowing waters is based on the fact that some species and groups of species are sensitive to alterations in water bodies and are affected by the anthropic impact in different ways. In particular, the water pollution, the simplification of riverbeds or their morphology with the consequent reduction of natural habitats, and the alteration of the hydrological regime allow the development of low-diversity populations (tolerant and rapidly developing taxa). Therefore, on the basis of the variations of macrophytic populations, the analysis of the macrophyte community provides overall indications on the alteration level of the water bodies caused by anthropic pressures. The IBMR is based on a list of 210 indicator taxa which are sensitive to the concentrations of ammoniacal nitrogen and orthophosphates. However, the trophic state is determined not only by the concentration of nutrients but also by other factors such as brightness (iaffected by turbidity and shading) and speed of the current.

The index provides a summary assessment of the fluvial functionality and the causes of its deterioration, as well as precise guidance for redevelopment measures and a prior assessment of their effectiveness. Through the analysis of morphological, structural and biotic parameters of the ecosystem, which are interpreted according to the principles of fluvial ecology, the functions associated with them are detected, as well as the possible deviation from the maximum functionality condition, identified than an ideal reference model. To determine the index, it is necessary to sample the benthic invertebrate communities (see EBI and STAR_ICMi).

ESW defines the ecological status of water bodies’ surface as an expression of the complexity of aquatic ecosystems and the chemical and physical nature of water, considering the status of the biotic elements of the ecosystem as a priority. This index is built up by integrating the results obtained from the application of two sub-indexes and considering the worst result between the two: The Extended Biotic Index (EBI) and the Macro-descriptors Pollution Level (LIM, which provides for the determination of chemical-physical and biological parameters, as referred to in Table 7 of Legislative Decree 152/99 and subsequent amendments and additions).

The CARAVAGGIO Method (Core Assessment of River hAbitat Value and hydromorpholoGIcal cOndition) allows the timely detection of a wide range of hydromorphological and habitat characteristics, fulfilling the requirements of Directive 2000/60/EC; it also provides a qualitative estimate of the extent of the impacts due to the presence of artificial structures and / or anthropic interventions along the waterway axis. The method is however functional to the collection of qualitative-quantitative data at different spatial scales, to be used for conservation, monitoring and/or prevention purposes.

The MQI is the national evaluation method in application of Directive 2000/60/EC as established by the Decree of the Ministry of the Environment, Territory and Sea Protection No. 260 of 2010. It is a parametric method which evaluates whether human activities influence the natural evolution of a watercourse. The evaluation of the morphological state is carried out considering the geomorphological “functionality”, the artificiality and the morphological variations, which together contribute to the formation of the index. The MQI is calculated on the basis of successive steps of analysis, according to a hierarchical approach: first on a basin scale, then on a macro-stretch scale (segments), and finally on homogeneous stretch scale. For the last one, reconnaissance, analysis and punctual detection of morphological and anthropic characters are expected.

The Ecological Status of the Fish Communities is normally estimated by the NISECI index (formerly ISECI) in the internal water ecosystems among the national territory. The parameter estimates the natural status of the community (calculated on the presence of endemic species expected for the zoogeographic framework of reference, as well as the presence / absence of alien species) and its ecological health’ status (that can be derived from the analysis of dynamics ecological resources, such as the average age of the population and the ability to recruit). Further additions to the method make it possible to adapt the index to the European Water Directives (especially the Water Framework Directive 2000/60/EC), by introducing descriptors of the reference conditions for each water context and the identification of standardized indicator elements.