Conclusiones y recomendaciones

The results of the optimization procedure, expressed by equation (3.18), are graph- ically presented in Figure 5.7. In Table 5.17 are reported the obtained values. Suitable sites for the intake have been localized along all the three considered branches of the Bussento river. The choice of the turbine type has been made case to case, as previously said. The major earnings are leaded by sites characterized by high hydraulic jump and large contributing area, in fact these sites are localized near the middle of each branch, where is achieved the better compromise between these quantities. From Figure 5.17 it can be seen that the highest earnings should come from plants situated along the branch A. This is because along that the river leads the highest slopes, and the contributing area is relatively high. It can be seen also that along a tract of the upstream part of the branch B the potential hydropower has not been evaluated: this is becouse here the river bed slope is too low, and plants with the fixed forced pipe lenght cannot have a sufficient hydraulic head. In four cases the obtained NPV value is negative: these sites are characterized by low hydraulic head and can not be exploited profitably (neither using Kaplan turbines), because revenues are lower than costs even if qD = qNPV.

Maybe particular turbines, specifically projected for small hydraulic heads and limited flows (on average less than 1 m3_{), are suitable for the exploitation of these}

LEGEND NPV > 4 M€ 2 M€ < NPV < 4 M€ 0 M€ < NPV < 2 M€ NPV< O M€ 1 3 6 9 11 15 8 7 4 13 5 16 10 14 2 12 (A) (B) (C)

5.3 Estimate of the hydropower potential 53

Intake A sq rq H Turbina MFD hqi qNPV NPV [km2] [-] h m3 s i [m] [-] h m3 s i h m3 s i h m3 s i [Me] 1 13.00 3.74 6.67 150 P 0.16 0.56 0.86 7.72 2 6,63 3.74 13,03 228 P 0,08 0,29 0,38 5.58 3 16.40 3.74 5.26 95 F 0.20 0.71 0.87 4.90 4 30.45 3.74 2.84 49 F 0.39 1.32 1.44 3.56 5 7.74 3.74 11.16 112 P 0.09 0.33 0.46 2.97 6 18.00 3.74 4.80 59 F 0.22 0.77 0.85 2.55 7 31.92 3.74 2.71 35 F 0.41 1.38 1.34 1.90 8 7.70 3.74 11.26 77 F 0.09 0.33 0.36 1.38 9 11.70 3.74 7.38 52 F 0.14 0.51 0.50 1.09 10 5,08 3.74 17,01 82 F 0,06 0,22 0,23 0.88 11 34.04 3.74 2.54 24 K 0.43 1.47 1.32 0.82 12 4,71 3.74 18,34 77 F 0,05 0,20 0,21 0.74 13 36.10 3.74 2.39 17 K 0.46 1.56 1.04 -0.08 14 5,05 3.74 17,11 30 K 0,06 0,22 0,09 -0.13 15 9.83 3.74 8.79 25 K 0.12 0.43 0.23 -0.15 16 32.22 3.74 2.68 15 K 0.41 1.39 0.65 -0.37

Chapter 6

Conclusions

The aim of this work is the evaluation of the hydropower potential of the Bussento river. For this purpouse the hydrologic regime has been studied. To this aim, the probability density function of the streamflows has been modeled using a stochas- tic approach that explicitely includes informations about climate and landscape attributes.

The hydrologic regime has been modeled on the basis of two different data sets, one concerning the period 1954-1968 and one concerning the period 2002-2012. Because of the lack of discharge data in the period 2002-2012, the model is calibrated during the years 1954-1968, and then is applied to the period 2002-2012.

Using the obtained probability density function of the specific streamflows, an analysis of the hydropower potential of the Bussento river has been carried out. The evaluation evidenced a set of economically profitable sites for the plant intake, and the corresponding plant capacities.

The most significant results of this work are listed below.

• A preliminary analysis of the data sets has shown the complexity of the hydrologic regime of the Bussento river. The karstic territory in which the catchment is situated and the presence of external contributions lead to runoff coefficients that are very variable at monthly and annual timescales. In par- ticular, runoff coefficients are, on average, <1 in cold and rainy months, and >1 in the rest of the year. The baseflow defined as the portion of the stream- flow which has no causal relationship with flow generating rainfall events. Being the river discharges, in each season and in different measure, consti-

tuted by a fraction of baseflow, due to slow runoff, carryover and external contributions which cannot be directly quantified, only with an analysis of the flow regime and of the rainfall precipitation done on a longer timescale it is possible to understand and therefore describe the dynamic of the baseflow. • The presence of baseflows significantly complicates the analytical description of streamflows dynamics and flow regimes. The complexity of the hydrologic regime leads to a necessary modification of the standard hydrologic model. The subdivision of the discharge into two different components permits a good representation of the hydrologic regime by means of physically mean- ingful quantities. In particular, the process of flow producing events has been splitted into two independent processes: the generation of hypodermic (fast) flow (with frequency λH), and the production of slow flow (with frequency

λS). Slow runoff subtracts an amount of water to the root zone. Such water

is released from the catchment as baseflow within longer timescales. These slow flows, jointly with the contribution of external sources, constitutes the baseflow of the Bussento river.

Baseflow contributions to streamflows are well represented by a gamma dis- tribution whose parameters have been calibrated based on the observed mean and variance of mean daily rainfall. Causal relationships between seasonal baseflow and precipitation have been identified through regression analysis. The method proposed for the modelization of the river flow regime in presence of baseflow well represents the hydrologic behavior of Bussento at Caselle in Pittari.

• From the preliminary analysis done in this study, the Bussento river at Caselle in Pittari basin is suitable for the installation of run-of-river power plants.

In particular, 16 sites have been found to be suitable to host the plant intake. These are situated along the three small branches of the river, upstream of the main valley where the outlet of Caselle in Pittari is located. In these sites the relative contributing area is much smaller than the area of the entire catchment where the hydrologic regime is analiyzed. This leads to a significative uncertainty in the estimate of the flow PDF used to analyze the earnings from the energy selling.

57 The method has allowed a proper evaluation of the maximum hydro-potential of the considered catchment. Nevetheless, given the complexity of the hy- drologic regime found for the whole basin, it is reasonable to think that each suitable sub-basin would deserve a more specific analysis of the hydrological regime. In particular, the external contributions and the baseflows could be highly heterogeneous in space, thereby, implying a pronounced heterogeneity of the flow regime along the stream network.

Bibliography

[1] Basso, S., G. Botter (2012), Streamflow variability and optimal capacity of run-of-river hydropower plants, Water Resources Research

[2] Bertacchi, P., G. Celentani, G. Marchetti (1990), Indagine sulle risorse idroelet- triche minori nel mezzogiorno d’Italia, Convegno nazionale sulle prospettive di sviluppo nel Mezzogiorno e condizioni di operativit¨ı£¡ del settore.

[3] Botter, G., S. Basso, I. Rodriguez-Iturbe, and A. Rinaldo (2013), Resilience of river flow regimes, Proc. Natl. Acad. Sci. U.S.A.

[4] Da Deppo, L., C. Datei, P. Salandin (2011) Sistemazione dei corsi d’acqua, DiCEA, University of Padova

[5] Lazzaro, G., S. Basso, M. Schirmer, and G. Botter (2013), Water manage- ment strategies for run-of-river power plants: Profitability ad hydrologic impact between the intake and the outflow, Water Resources Research

[6] Marani, M., Processi e modelli dell’idrometeorologia. Un’introduzione, DiCEA, University of Padova

[7] Consulted site: http : //www.isprambiente.gov.it [8] Consulted site: http : //sit.regione.campania.it