**3.3 Study area: Beliche and Odeleite reservoirs**

Beliche and Odeleite reservoirs are located on two small affluent streams to the Guadiana estuary (Fig. 8), and were built for purposes of drinking water production. They are interconnected by an underground water channel, with sluices that are operated by the managing authorities, whenever they need to transfer water from Odeleite to Beliche reservoir. Together these reservoirs constitute the raw water source for 230,000 inhabitants of eastern Algarve, a province on the south coast of Portugal. Since Algarve constitutes an important national and international tourism destination, summer population more than

Fig. 8. Location of Beliche and Odeleite drainage basin

For their intercalibration exercise, the Med GIG agreed on using chlorophyll *a* and total biovolume as phytoplankton biomass indicative parameters, and elected three phytoplankton composition metrics, namely the contribution of cyanobacteria to total phytoplankton biovolume, the General Algal Index (GAI - Catalàn et al. 2003) and the Mediterranean Phytoplankton Trophic Index (MedPTI - Marchetto et al. 2007). Although recognizing strong limitations of the dataset used and the fact that not all tipologies of Mediterranean lakes and HMWBs were covered, actual law enforcement stipulates that ecological potential of the reservoirs in the Guadiana watershed should be classified, according to the proposed metrics. However, application of such phytoplankton composition metrics to CHABs management

The following case study constitutes an effort to evaluate the Med GIG selected ecological indicators when applied to water management strategies for the Guadiana watershed. Different phytoplankton metrics determined for two reservoirs and compared in order to assess their usefulness in CHAB management, taking in consideration the EPA Guidelines

Beliche and Odeleite reservoirs are located on two small affluent streams to the Guadiana estuary (Fig. 8), and were built for purposes of drinking water production. They are interconnected by an underground water channel, with sluices that are operated by the managing authorities, whenever they need to transfer water from Odeleite to Beliche reservoir. Together these reservoirs constitute the raw water source for 230,000 inhabitants of eastern Algarve, a province on the south coast of Portugal. Since Algarve constitutes an important national and international tourism destination, summer population more than

for Evaluation of Ecological Indicators (Jackson et al., 2000)

**3.3 Study area: Beliche and Odeleite reservoirs** 

Fig. 8. Location of Beliche and Odeleite drainage basin

has yet to be assessed.

doubles and puts water demand at its peak during the high season (June through September), coinciding with low precipitation and high atmospheric temperature. Table 1 presents important features of these two reservoirs, where the most notorious aspects are the ones relative to their catchment area. While other reservoirs from the Guadiana watershed contributed to extensive development of irrigation (eg. Alqueva), promoted by the use of EU subsidies that encouraged high value intensive crop production (Varela Ortega et al. 1998, Varela-Ortega et al. 2003), the catchment areas of these two streams do not support any significant economic activity (Fig. 8).

Historical reasons linked to deforestation and farming mal-practices, back in the 30s of the XX century, led to extensive soil erosion, agriculture relinquishment and human desertification. Indeed, these catchment areas are the poorest counties in Portugal, with population densities around 20 habitants /Km2. Human settlements are small villages concentrated downstream of the catchment area. In order to rehabilitate the landscape there has been a large investment in replanting pine woods with the objective of developing new soil and future stimulation of natural vegetation. Apart from some small goat herds in the Odeleite watershed and extensive cropping of sparse almond trees, there are no human impacts, no sewages, no pig style farms, no intensive or extensive farming. From a CHAB prevention point of view, it is difficult to point out what could be improved for the protection of their drainage basins.


Table 1. Beliche and Odeleite reservoirs location and some main features. (Data source: http://snirh.pt/)
