Overall Assessment LOCAL CLIMATE PROFILE
Coordinator
The City of Bologna covers an area of approximately 14 hectares, has a population of about 380,000 inhabitants, and is a strategic hub of the national road and rail network. The local economy is based on small and medium-sized enterprises, which have a reputation of prestige and national importance, and that contribute greatly to the richness of the territory. [email protected] - [email protected]
Partner
Kyoto Club is a non-profit organization founded in February 1999. Its members are business companies, associations and local municipalities and governments engaged in reaching the greenhouse gases reduction targets set by Kyoto Protocol. [email protected]
Ambiente Italia is accredited as an expert European center for urban and environmental policies and has been approved as ESCO from the Italian Energy Authority. It is partner with the Sustainable Energy Europe Campaign and the Global Footprint Network. Ambiente Italia is the first Italian company accredited as a “Footprint Expert”. [email protected]
ARPA is the Regional Agency for Environmental Protection in Emilia-Romagna.It is an environmental control technical support body to the regional and local authorities and is administratively and technically independent. Activities deal with monitoring and control related with all types of chemical, biological and physical pollution in all environmental media. [email protected]
Under evaluation of the BLUE AP Scientific Board
Summary Summary ...... 3 1. CLIMATE VARIABILITY AT LOCAL SCALE ...... 5 1.1. The observed climate variability at Bologna city ...... 5 1.1.1. The variability of observed minimum and maximum temperature: mean and extreme values ...... 10 1.2. The observed variability of seasonal and annual precipitation: mean and extremevalues………………...... 13 1.3. Climate change scenarios at Bologna over the periods 2021-2050 e 2071-2099 ...... 16 1.3.1. Climate change projections at Bologna: mean and extreme temperature .. 18 1.3.2. Climate change projections at Bologna: mean and extreme precipitation .. 22 2. LAND AND USE INFRASTRUCTURE ...... 24 2.1. Urbanized area and new transformations and/or urban settlements ...... 24 2.1.1. Artificial water canals ...... 24 2.1.2. Urban land to be structured...... 25 2.1.3. Population and urban density ...... 26 2.2. Land use…………………...... 28 2.3. Territorial infrastructures ...... 30 2.3.1. Artificial water canals ...... 30 2.3.2. Transport networks ...... 30 2.3.3. Energy networks ...... 31 3. HEAT WAVES AND HEAT ISLAND ...... 33 3.1. Measurement campaigns and alerts ...... 33 3.2. Distribution of urban green spaces and the most vulnerable population...... 36 Urban green spaces land local ecological network ...... 42 3.3. Interaction between climate change, pollution, pollen and health ...... 43 3.4. Climate change, new pests and health ...... 46 4. WATER SYSTEM AND HYDROGEOLOGICAL RISK ...... 49 4.1. Water System, Soil Drainage and Water Holding Capacity ...... 49 4.1.1. Surface water system...... 49 4.1.2. Waterproofing and drainage capacity ...... 50 4.2. Hydrogeological risk ...... 52 4.2.1. Surface Flood risk areas ...... 52 4.2.2. Surface Landslide risk areas ...... 55 4.3. Surface water quality and water treatment ...... 57 4.3.1. Surface water quality ...... 57 4.3.2. Sewage system ...... 58 4.3.3. IDAR Purification plant ...... 60 4.4. Water use and water scarcity ...... 61 4.4.1. IDAR Water taking and water consumption ...... 61
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4.4.2. Water taking ...... 61 4.4.3. Water consumption ...... 62 4.5. Water use in agriculture ...... 63 4.5.1. IDAR Water use in industry ...... 64 4.5.2. Water losses ...... 66 4.5.3. Agreements for water use in case of drought ...... 66 4.5.4. Final assessment, challenges, future scenarios ...... 68 4.6. Groundwater: Qualitative and quantitative status ...... 68 5. MAIN RESILIENCE FACTORS ...... 71 5.1. New building ………………………………………………………………………………………………………….71 5.2. Saving and management of water resource ...... 71 5.3. Stream requalification ...... 72 5.4. Increase and improvement of urban green areas ...... 73 5.5. Heat waves………………… ...... 74 6. CONCLUSIONS ...... 75 6.1. Rising of summer temperature and heat-island...... 75 6.2. Water crisis and drought ...... 76 6.3. Increase of intense weather events ...... 76
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1. CLIMATE VARIABILITY AT LOCAL SCALE
1.1. The observed climate variability at Bologna city
The IPCC AR4 (2007) concluded that the warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level. The analysis of historical time series of the main meteorological fields (for example temperature, precipitation) from different areas, contribute to the understanding of the past and present climate variability and also to the construction of future climate change scenarios using different tools. The climate analysis requires long time series, in order to estimate the significance of signal, and also large area in order to capture better the spatial variability (basin, region, continent).
This chapter is focused on the description of observed climate variability and future projections of the temperature and precipitation (mean and extreme values) at Bologna, the results being compared with those obtained at global, European and national scale. Also, the impact of present and future climate changes obtained at Bologna are discuss in terms of risks and vulnerability.
At global and European level, the WG1-IPCC report from 2007 (www.ipcc.ch) underlined significant changes in the observed climate variability, such as:
global mean surface temperatures have risen by 0.74°C ± 0.18°C when estimated by a linear trend over the last 100 years (1906–2005). The rate of warming over the last 50 years is almost double that over the last 100 years (0.13°C ± 0.03°C vs. 0.07°C ± 0.02°C per decade). The trend is not linear, and the warming from the first 50 years of instrumental record (1850–1899) to the last 5 years (2001–2005) is 0.76°C ± 0.19°C; at European level, the analysis of temporal variability of mean air temperature underlies that the warming was higher during the last decade. In addition the Iberian Peninsula, Central and N-E part of Europe are the areas that exhibits higher signal of warming; the analysis of precipitation shows significant trends in different regions of the world, from 1900-today. These trends presents different sign, for example: an increase has been noted in N-Europe, northern and central Asia while negative trends have been obtained over Mediterranean area, south part of Africa, Sahel.
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A complete framework of climate variability requires analysis focused not only on mean values, but also on extreme values. An extreme weather event is an event that is rare within its statistical reference distribution at a particular place. The extreme events could be defined through the thresholds specific to each place, for example using of the percentile : 5th,10th, 90th ,95th . By definition, the characteristics of what is called extreme weather may vary from place to place.
During the last century the frequency of extreme events in Europe has significantly changed. An increase in the frequency of extreme events associated to higher temperature and a decrease of the frequency of events associated with lower temperature have been observed. As concerns precipitation, an increase of intense precipitation and of dry events have been registered.
Similar signal of changes have been obtained at smaller scale, for example over Italian peninsula, Northern Italy, or Emilia-Romagna. Brunetti et al (2006) analyzing secular time series, found positive and significant trends in annual mean air temperature from Italian peninsula over the period 1880-2011. This signal has been confirmed at seasonal level by Toreti e Desiato (2010), more intense during summer than in the other seasons. Simolo at al., (2010) showed that an increase in the extreme events of temperature was recorded over Italian peninsula during the last decades, especially those extremes associated to maximum temperature. As regards precipitation, Brunetti et al. (2006), Toreti and Desiato (2010) detected over Italy a slightly negative trend in annual precipitation over long period, namely 1800-2011 (-0.58±0.15 %/decade), more intense in northern Italy than in the southern part. Studies focused over the last decades, emphasis that in northern Italy the slightly negative trends is maintained while in the southern part there is a tendency to increase of precipitation. This could be due to an increase in the frequency of intense precipitation during the last decades.
Similar signal of changes in temperature and precipitation has been detected over Emilia Romagna region. The spatial and temporal variability of temperature and precipitation has been analysed by ARPA-SIMC in the framework of ERACLITO project. The final product of the project is an hydro-climatic atlas of Emilia-Romagna, that includes: climatic maps of mean and extreme temperature and precipitation, over the period 1961-1990 , maps of changes over 1991-2008 with respect to 1961-1990 (Marletto et al.,2010). One example of map is presented in Figure 1a that displays the changes of annual mean air temperature over the period 1991-2008 with respect to 1961-1990. As could be noted, positive anomalies had been registered over whole region during the period 1991-2008, with value between 0.5°C and 3°C.
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a)
Temporal variability of annual anomalies of minimum and maximum temperature over Emilia-Romagna
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2.5 Tmax Tmin C)
° 2
1.5
1
0.5
0 anomaliesTmin/Tmax( -0.5
-1
-1.5 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 2011 years
b) Fig. 1. Spatial variability of the anomalies of annual mean temperature of the period 1991- 2008 with respect to 1961-1990 (a) and temporal variability of annual anomalies of minimum and maximum temperature over Emilia Romagna region (b).
Analysing in details the annual minimum and maximum temperature over Emilia Romagna region, positive trend has been detected over the period 1961-2011, more intense in maximum (0.5°C/decade) than in the minimum (0.3°C/decade) temperature. As could be noted in figure 1b the temporal variability of minimum and maximum temperature over the region presents an intensification of the anomalies especially after 1990. Similar signal of trend has been detected at seasonal level, with anomalies more intense during summer: 0.65°C/decade for maximum temperature and 0.4°C/decade for minimum temperature. The analysis of extreme temperature revealed an increase in 10th and 90th percentile associated
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with a decrease in winter frost days and an increase in summer heat waves, over the period 1958-2000 (Tomozeiu et al., 2006).
As regards the precipitation over Emilia-Romagna, negative anomalies had characterized the last two decades (figure 2a), while over long period (1961- 2011) a slightly negative trend of annual precipitation had been noted (figure 2b).
a)
b)
Fig. 2.Spatial (a) and temporal (b) variability of anomalies of annual precipitation over Emilia- Romagna region. The spatial variability is referred to 1991-2008 with respect to 1961-1990.
Seasonally, a slightly negative trend had been recorded in winter, spring and summer precipitation while a positive trend had been obtained during autumn. As regards the extremes of precipitation, Pavan et al.,(2008) founded negative trends in the number
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of wet days during winter and spring and positive trend for the number of days with intense precipitation during summer season.
In the followingthe results of observed climate variability focused on Bologna city are presented The analysis over Bologna has been done using daily minimum and maximum temperature, and precipitation registered by the historical station of Bologna. The station was initially placed in via della Zecca, (25/06/1934 to 31/12/1953), then has been moved to Piazza VIII Agosto (height 51m., latitude 44°29’36’’ and longitude 01°06’25’’). Figure 3 shows sensors of the climatic station of Bologna.
Fig. 3. Meteorological station- Bologna
The daily data has been quality controlled and homogenized. The following climatic indices had been selected, computed and analyzed at seasonal and annual level, in order to construct present and future climate profile for Bologna city:
seasonal and annual minimum (Tmin) and maximum temperature (Tmax); the 90th percentile of maximum temperature (Txq90); the 10th percentile of minimum temperature (Tnq10); the number of frost days, defined as the number of days when the minimum temperature is under 0°C (Fd) the number of ice days, defined as the number of days when the minimum and maximum temperature are under 0°C (Txice) heat wave duration (HWD), defined as the maximum number of consecutive days with maximum temperature greater than 90th
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percentile. This index has been computed for each season and particular attention has been paid on summer. seasonal and annual amount of precipitation (prec); the number of days with precipitation greater than 90th percentile; the number of consecutive dry days, defined as the maximum number of consecutive days without precipitation (pxcdd).
The above indices were selected such as to describe the intensity and the frequency of extreme events. Trend analysis have been performed for each index, season and the significance of trends has been tested through statistical test (Kendall-Tau test).
1.1.1. The variability of observed minimum and maximum temperature: mean and extreme values
The analysis of annual minimum and maximum temperature registered at Bologna emphasis a positive trend over the period 1951-2011, more intense in the maximum (0.3°C/decade) than in the minimum (0.2°C/decade). As underlined over Emilia Romagna region, also for Bologna the signal of warming became more intense after 1990, when peak of 2.5°C of anomaly had been registered (figure 4a). The positive trend of temperature has been detected also at seasonal level, more intense during summer and especially after 1990 when peaks up to 4°C of anomalies had been registered (for example on 2003, figure 4b).
Annual variability of minimum and maximum temerature anomalies- Bologna 3.5
3.0 C)
° Tmin Tmax 2.5
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anomaies( 1.5
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0.0 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 2011 -0.5
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The variability of summer minimum and maximum temerature anomalies- Bologna
5.0
C) ° 4.0 Tmin Tmax
3.0 anomalie(
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0.0 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 2011 -1.0
-2.0
-3.0 years
b)
Fig. 4. The temporal variability of the minimum and maximum temperature anomalies – Bologna: annual (a) and summer (b) anomalies time series
Table 1 presents the trend coefficient of minimum and maximum temperature at Bologna, seasonal and annual values, computed over the period 1951-2011 (first and third columns) and the climatic value (second and last columns).
Season Trend Climate Trend Climate (°C/decade) reference (°C/decade) reference Tmin (’61-’90) Tmax (’61-’90) Tmin Tmax
Winter (DJF) 0.4* 1 0.4* 7
Spring (MAM) 0.3* 10 0.2* 18
Summer (GLA) 0.3* 19 0.3* 29
Autumn SON) 0.2* 11 0.3* 19
Annual 0.3* 10 0.2* 18
Tab. 1. Trend over the period 1951-2011 and climatic values over the period 1961-1990 at Bologna for Tmin and Tmax. The significant values are marked by stars.
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A similar tendency of increas has been detected analyzing the extreme temperature. For example, 10th percentile of minimum and 90th percentile of maximum temperature exhibits positive and significant trends for each season and at annual level, more intense in the 10th percentile of Tmin and especially during winter (0.6°C/decade) and spring (0.4°C/decade). Table 2 reports the coefficient of trends for 10th of Tmin (Tnq10), number of frost days(Fd), number of ice days (Txice), 90th percentile of Tmax (Txq90).
Season Trend Trend Trend Trend (°C/decade) (days/dec.) (°C/dec.) (°C/dec.) Tnq10 Fd Txice Txq90
Winter (DJF) 0.6* -4* -1* 0.3*
Spring (MAM) 0.4* -4* n.s. 0.2*
Summer(JJA) 0.3* - - 0.3*
Autumn(SON) 0.3* -1 n.s. n.s
Tab. 2. Seasonal values of trend coefficient of extreme temperature over the period 1951-2011, Bologna. The values significant at 95% are marked by stars, while the values that are not significant are marked by n.s.
As could be noted from table 2, the increase in the 10 th percentile of minimum temperature connect to a decrease of the number of frost days, significant during winter and spring (4 days/decade). An important signal has been detected also in extreme of maximum temperature, especially in the heat wave duration. The heat wave duration is defined as the maximum number of consecutive days with maximum temperature greater than the 90th percentile computed over the 1961-1990 period. During summer, at Bologna the climatic value of seasonal percentile is 33.7°C. Figure 5 presents the evolution of the summer time series heat wave duration (continuous line) and the climatic value of the index (dashed line). As it could be noted, the climate value of the index is around 3 days (green line), but during the last two decades the index registered high value (up to 12 consecutive days).
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The variability of summer heat wave duration(HWD) index at Bologna
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12
10
8 days
6
4
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0 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 2011
years HWD climate_HWD
Fig. 5. The evolution of the time series of heat wave duration (continuous line) and the climatic value of the index (dashed line)
1.2. The observed variability of seasonal and annual precipitation: mean and extreme values
The quantity of precipitation registered at Bologna shows a slightly negative trend during winter, spring, and summer and a positive trend during autumn, over the period 1951-2011. Figure 6a presents like an example the variability of summer anomalies of precipitation. As could be noted there are years with intense positive/negative anomalies, but during the last decade negative anomalies have been frequently registered.
As regards seasonal extreme of precipitations, it has been noted that the dry days index present a positive trend over 1951-2011 period, more intense during summer. Figure 6b presents the temporal variability of maximum number of consecutive dry days during summer. As it could be noted from figure 6b, the index presents a climatic value around 15 days, but, the last decade registered high value ( up to 50 days consecutive without precipitation).
A slightly positive trend has been detected also in the frequency of days with intense precipitation in all season, except on spring when a slightly negative trend has been
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observed. Figure 6c displays like an example the temporal variability of this index during summer.
200 Temporal variability of the summer anomalies of precipitation -Bologna 1951-2011 150
anom_prec(mm) 100
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0
-50
-100
-150 1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 2011 years
a)
60 days Temporal variability of the number of dry days during summer 50 season- Bologna (1951-2011)
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0 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 2011
years
b)
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6 Temporal variability of the frequency of number of days with intense
precipitation -summer, Bologna days 5
4
3
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0 1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 2011
years
c)
Fig. 6. The variability of the anomalies of precipitation, consecutive dry days and the number of days of intense precipitation- Bologna
These results underlined that, as regards observed climate variability at Bologna over the period 1951-2011, important changes had been noted in minimum and maximum temperature associated to positive and significant trend at seasonal and annual level. In addition, an increase in heat wave had been noted in each season, more intense during summer and a decrease in winter frost and ice days. The precipitation presents a slightly negative trends in all season with except to autumn when a slightly increase in the quantity of precipitation had been observed. An increase in the dry days and intense precipitation has been detected in summer, especially during the last decade.
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1.3. Climate change scenarios at Bologna over the periods 2021-2050 e 2071-2099
The best tools made available by the climate community, in order to evaluate the future climate projections over different spatial and temporal scale, are the coupled global climate models (AOGCMs). The spatial resolution of the global models has been improved in the last time arriving to 100km. Unfortunately, this resolution is not sufficient for the impact studies, such as an increase of resolution is requested in order to study the impact of climate changes at local scale. The dynamical and statistical downscaling methods are used to reach this objective. The dynamical downscaling uses limited-area, high-resolution models (regional climate models - RCMs) driven by boundary conditions from global climate models so as to derive local-scale information, while the statistical downscaling (SD) is based on the statistical relationship that links the large-scale atmospheric variables (predictors) and local/regional climate variables (predictands). The statistical downscaling technique presents the advantage that is not expensive in terms of computational time and the climate signal could be constructed at the station/grid point requested by the end- users. One major problem for all tools mentioned before is to quantify and reduce the uncertainties that appear in modeling processes. Particular attention has been paid on this problem and many projects have been focused on this issue. One of this is Ensembles project (http://www.ensembles-eu.org/), where it was recommended use of a range of models over the same area and construction of an ensemble mean (EM).
In the present study, the climate change projections at Bologna are obtained through the statistical downscaling model (SD) developed by ARPA-SIMC. The model is a multivariate regression based on canonical correlation analysis applied at seasonal level (CCAReg model). Through the canonical correlation analyses is detected the link between “large scale fields” , that are actually best represented by GCMs ( for example mean sea level pressure, geopotential height at 500 HPa, temperature at 850hpa), and “local fields” (minimum, maximum temperature or total amount of precipitation).
The data set used in the construction of the model includes:
Daily minimum, maximum temperature and precipitation measured over 25 stations from Emilia-Romagna region over the period 1958-2002 (figure 7). These data have been used in order to compute mean and extreme events of temperature and precipitation at seasonal scale; Large scale fields (mean sea level pressure, geopotential height and temperature at 850 hPa) from ERA40 reanalysis that covers the period 1958-2002.
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Fig. 7. Map with stations used in the set-up of statistical downscaling model (SDs)
The statistical downscaling models have been constructed for each season and variables (mean and extreme fields) using observed data that belong to the periods: 1958-1978+1995-2002 and were validated over the period 1979-1994 (Tomozeiu et al., 2013). The correlation coefficient, BIAS and root mean square error, computed between observed and downscaled data, have been used to test the performance of the SDs. Ones the best statistical scheme has been identified in the set-up phase, to this scheme are then applied the large scale predictors simulated by the GCMs, available in the framework of ENSEMBLES project (http://ensembles- eu.metoffice.com/; Van der Linden e Mitchel, 2009) such as to construct climate change projections at station level, over the period : 2021-2050 and 2071-2099. The global climate models used in the present work are: IPSL, METOHC, MPIMET, INGV- CMCC e FUB(2 runs) while the emission scenario is scenario A1B. Finally, for each season and variable the SDs constructed from the observed data have been applied to the 6GCMs and finally 6 scenarios have been obtained at local scale for each season/variable. An Ensemble Mean has been computed for each season/local predictands.
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1.3.1. Climate change projections at Bologna: mean and extreme temperature
Climate change scenarios of seasonal minimum and maximum temperature obtained through statistical downscaling technique applied to the 6GCMs experiments, estimate a possible increasing in both minimum and maximum temperature at Bologna, in all seasons and over both periods: 2021-2050 and 22071-2099 with respect to 1961-1990.
Figure 8a presents like an example the PDFs of winter Tmin changes projected at Bologna over the period 2021-2050 while the Ensemble Mean of projected changes is presented in Figure 8b. As could be noted, all the models project an increase between 1°C (for example EGMAM_run1, INGV) to 1.5°C (for example IPSL). This increase of temperature lead to a shift of whole distribution to “warm” value, as could be noted also from figure 8b, that displays the Ensemble Mean of changes, with an increase not only in the mean value but also in the extreme (shift in the tails of the distribution).
Climate change projections of winter Tmin, scenario A1B 2021:2050-1961:1990 Bologna
changes Tmin (°C)
CCAReg_ingv CCAReg_egmam_r1 FunctionDensityProbability CCAReg_egmam_r2 CCAReg_meto_hc clima_1961-1990 CCAReg_echam5 8 a)
Fig. 8a. PDFs of winter Tmin changes projected at Bologna (multi-model) over the period 2021- 2050
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8 b)
Fig. 8b.Climate change projections of winter minimum temperature-Bologna (Ensemble- Mean), 2021-2050 with respect to 1961-1990 .
A similar signal of changes has been obtained for the other seasons, with the peak of increasing during summer when the projected changes is around 2.5 °C , over the period 2021-2050 with respect to 1961-1990 period.
The warming becomes more pronounced going to the end of the century, namely to the period 2071-2099, when the projected increasing in minimum and maximum temperature (central value of the probability distribution function) during winter, spring and autumn is between 3-4°C and around 5.5°C during summer season. As in the case of first period, a shift of the distribution to the “right” is also obtained over 2071-2099.
Table 3 summaries the mean values of future changes at Bologna, projected by the statistical downscaling scheme applied to the GCMs for seasonal minimum and maximum temperature, over the periods 2021-2050 and 2071-2099(Ensemble Mean- EM).
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Winter Spring Summer Autumn
Tmin 2021 2050 1.2°C 1.6°C 2.5°C 1.7°C
Tmax 2021 2050 1.5°C 2.1°C 2.5°C 2°C
Tmin 2071-2099 2.8°C 3.7°C 5.5°C 3.4°C
Tmax 2071 2099 3°C 4.1°C 5.5°C 4°C
Tab. 3. Climate change projections (EM) of seasonal minimum and maximum temperature at Bologna, over the periods 2021-2050 and 2071-2099.
As could be noted from table 3 the projected increases in minimum temperature are in generally closed to those ones in maximum temperature.
The analysis performed on extreme temperature reveals important future changes. An increase in seasonal 10th percentile of minimum temperature of 1.5°C in the first period and 3.5°C in the second period, has been projected by the statistical scheme. It is important to underlay that as concerns the 10th percentile of minimum temperature, the projected changes over the period 2071-2099 could connect to a values of percentile close to 1°C with respect to -2.7°C that characterized the 1961-1990 period, so a future change not only of the magnitude of 10th minimum temperature but also of the sign. This could connect also to a decrease in the number of frost days. In fact, the scenarios constructed for the number of frost days emphasis a decrease during winter, spring and autumn, more pronounced at the end of the century. Figure 9 shows the projected changes of the seasonal frost days and ice days (when maximum temperature is below 0°C)over both periods: 2021-2050 and 2071-2099.
DJF MAM SON 0 -2 -4 -6 -8
-10 changes(days) -12 -14 -16
EM Tnfd 2021-2050 EM Tnfd 2071-2099
EM Txice 2021-2050 EM Txice 2071-2099
Fig.9. Climate change projections of seasonal number of frost days (Tnfd) and ice days (Txice) at Bologna, over 2021-2050 and 2071-2099 with respect to 1961-1990, scenario A1B
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As regards summer extremes temperature, the projections shows important changes also in 90 th percentile of maximum temperature , with an increase especially at the end of the century when the index could reach 40°C with respect to 33.7°C of the present climate (1961-1990). This is associated also with an increase in the number of heat waves, namely the maximum number of consecutive days with maximum temperature greater than 33.7°C. Figure 10 presents an example of climate scenarios of seasonal heat wave at Bologna, present and future climate .
Scenario of heat wave duration index at Bologna station, outputs of the SDs- Ensemble Mean, scenario A1B, periods: 1961-1990, 2021-2050, 2071-2099 12
10
8
6
4 HWD(days)
2
0 DGF MAM GLA SON seasons
clima 1961-1990 hwd_2021-2050 hwd_2071_2099
Fig. 10 Observed and projected seasonal heat waves at Bologna.
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1.3.2. Climate change projections at Bologna: mean and extreme precipitation
The statistical downscaling techniques developed for the seasonal precipitation and applied to each GCM reveals in generally a decrease of precipitation over both periods 2021-2050 and 2071-2099. During the first period, the projected decrease is around - 5% during winter (not significant from the statistical point of view) and around -15% in the other seasons (figure 11). The signal is more pronounced at the end of the century and especially during summer (-30%). As regards extreme of precipitation, the projections show a possible increase in the maximum number of consecutive dry days , especially during winter spring and summer, and an increase in the summer intense precipitation.
Projected values of changes in mean daily precipitation (%) at Bologna station, outputs of the Ensemble Mean, scenario A1B DGF MAM GLA SON
0
-10 changes changes (%) -20
-30
-40
2021-2050 2071-2099 seasons Fig. 11. Scenario of seasonal precipitation obtained through statistical downscaling technique applied to 6GCMs (Ensemble Mean) at Bologna , over the periods 2021-2050 e 2071-2099.
Similar results have been obtained by the regional climate models (RCM), that underlined a possible increase in mean air temperature of 2°C over great part of Europe, for the period 2021-2050 with respect to 1961-1990 (http://ensembles-
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eu.metoffice.com/). In addition a decrease in precipitation, more intense during summer (up to 40%) have been projected over Mediterranean area.
Conclusions: present climate variability and future scenarios at Bologna
The results of present and future climate variability at Bologna could be summarised as follows:
positive and significant trends of seasonal minimum and maximum temperature over the period 1951-2011 (around 0.3°C/decade) have been detected. During the analyzed period, an increase in the heat wave duration , especially during summer, and a decrease in winter frost and ice days has been founded. These signals became more intense after 1990, when strong and positive anomalies in temperature have been recorded ( for example summer 2003, winter 2007-2008) as concerns observed precipitation, the signal of trend is different from season to season. A slightly decrease have been observed during winter, spring and summer, while a slightly increase has been noted during autumn. The observed consecutive dry days shows an increase during summer season, when it was noted also an increase in the frequency of the number of intense precipitation. the future scenarios constructed through the statistical downscaling scheme applied to GCMs show a possible increase in the minimum and maximum temperature, around 2°C over the period 2021-2050 with respect to 1961-1990. The increase is more pronounced to the end of the century, and especially during summer , when the anomalies could reach 5.5°C respect to present climate. This will lead to a possible increase in the heat wave duration. As regards precipitation, a reduction of the amount has been projected during all seasons, more intense to the end of century and especially during summer season (reduction around 30% ).
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2. LAND AND USE INFRASTRUCTURE
2.1. Urbanized area and new transformations and/or urban settlements
2.1.1. Artificial water canals
The urbanized area of the Municipality of Bologna increased from 19,35 Km2 in 1951 to 47,74 Km2 in 2003 (about 4,25 Km2 representing the old city), equivalent to 34% of the whole city surface. In 50 years the urbanized area has grown more than 200%, occupying approximately 20% of the vacant land.
The large and fast expansion of the city started slowing down at the beginning of the 90’s: from 1981 to 1989 there was an increase of urbanized areas of about 562 hectares, an annual mean of 70 hectares (comparable to the mean of 68 hectares per year of the decade 1971- 1981), while from 1989 to 2003 the average annual consumption decreased to 19 hectares per year, accounting for a total land consumption of 272 hectares during those 14 years.
Table 4. Evolution of land consumption (1951-2003)
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In the PSC – the Bologna urban plan (Table 1) - the structured urban land areas (Historical areas, consolidated planned area, consolidating areas, consolidated diffused areas, areas to be regenerated) and the other ones that are going to be structured (transformation areas, replacement areas) are about 65 Km2 (47% of municipality surface). The new urban settlements correspond to 4,05 Km2, and they represent an increase of 6% of the urbanized area.
2.1.2. Urban land to be structured
The urban land to be structured is composed by three different areas.
New settlement areas: part of the territory that is under an intensive transformation process due to the new urbanization and the expansion of urban pattern. Replacement areas: the intensive transformation comes from a “replacement of relevant part of the built up area” process. Transformation areas: new urban planning programs have been approved (or adopted, or under way), during the implementation of the existing urban plan (PSC).
Table 1 (PSC-Urban Plan)
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The portion of the urbanized territory in which the Bologna’s PSC predicts the most relevant transformations are the “Replacement areas”, made up of those part of the territory in which the intensive transformation involve a total change of the existing urbanized areas. All of these areas have a mixed destination, that means they are characterized by the presence - at the same time - of social, cultural, commercial and productive activities together with residence: among them Prati di Caprara (400.000 m2) and the ex-railway yard Ravone (320.000 m2), located in the north-west of the city.
2.1.3. Population and urban density
Population density in the city of Bologna is, on average, more than 2.700 inhabitants/km2, ranging from very compact and dense areas (more than 10.000 inh/km2), such as the historical and consolidated areas (Galvani and Murri – Santo Stefano neighbourhood, Irnerio – S. Vitale, Malpighi - Saragozza, Marconi - Porto) to less dense areas (below 1.000 in/ km2), i.e. the agricultural Borgo Panigale neighbourhood and the hillside area Colli, located in S. Stefano district.
Table 2 (Population density)
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Densità popolazione anno 2011
Quartiere Zona Pop residente Sup (km2) Densità
Borgo Panigale Borgo Panigale 25.350 26,2 968,8
Bolognina 34.524 4,9 6.983,6
Navile Corticella 17.847 9,9 1.806,9
Lame 14.594 11,1 1.320,2
Marconi 14.189 1,1 13.407,5 Porto Saffi 17.914 2,7 6.712,2
Barca 20.912 3,3 6.295,2 Reno S. Viola 12.884 1,9 6.616,4
San Donato San Donato 31.661 15,5 2.047,3
Irnerio 13.921 1,4 10.120,2 San Vitale S. Vitale 33.779 10,8 3.126,6
Colli 8.443 25,1 336,8
Santo Stefano Galvani 13.162 1,1 11.785,6
Murri 28.391 2,8 10.058,8
Costa Saragozza 24.208 10,7 2.254,2 Saragozza Malpighi 12.230 1,0 12.744,9
Mazzini 37.699 5,7 6.559,6 Savena S. Ruffillo 20.925 5,7 3.662,8
Totale 382.633 140,8 2.716,7 Tab. 5. Population density – Districts
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2.2. Land use
The land use map1 highlight how, among all uses, artificial areas stand out (residential, industrial and extracting areas), interposed with “not agricultural green areas” (urban green spaces, equipped green areas, etc.), that represent 54,5% of the territory. The urban fabric, which is consolidated in compact typology between the historical centre and the bypass- highway route, gradually recede, crossing the bypass-highway route with new big productive and commercial settlements.
Table 3 (Land use 2008)
As regards agricultural areas (33% of the territory), a clear distinction between hillside and level ground stands out from the land use map. The level ground is characterized by arable fields largely interposed with agriculture, especially vineyard and orchard, . On the opposite, the hill represents the real natural part of Bologna. The first belt, next to the urban centre, is characterised by sparse settlements, while over this built belt, land uses become exclusively agricultural, wood and grassland.
1 Source: Uso del suolo Regione ER, 1:25.000, Anno 2008.
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More than 11% of the territory is covered by woods and natural environments, in particular forests (5,6%), shrubbery and herbaceous areas (4,7%).
Comparing the land use between 2003 and 2008, there is an increase of artificial areas over agricultural ones (arable fields, permanent farming and agricultural fields), while, in the same period, stable grasslands register an increase. Woods and semi-natural environments don’t have significative changes.
Categorie Uso suolo 2003 Uso suolo 2008 Var. Codice Descrizione Sup (ha) % Sup (ha) %
1 Zone artificiali 7520,7 53,4 7679,3 54,5 +
11 Zone urbanizzate di tipo residenziale 3090,5 21,9 3167,0 22,5 +
12 Zone industriali, commerciali ed infrastrutturali 2549,6 18,1 2638,0 18,7 +
Zone estrattive, cantieri, discariche e terreni 13 409,4 2,9 462,2 3,3 + artefatti e abbandonati
14 Zone verdi artificiali non agricole 1471,2 10,4 1412,0 10 -
2 Superfici agricole utilizzate 4806,1 34,1 4654,3 33 -
21 Seminativi 4074,7 28,9 3933,9 27,9 -
22 Colture permanenti 270,7 1,9 258,5 1,8 -
23 Prati stabili (foraggere permanenti) 252,5 1,8 260,3 1,8 +
24 Zone agricole eterogenee 208,2 1,5 201,6 1 -
3 Territori boscati e ambienti semi-nat 1581,4 11,2 1582,5 11,2 =
31 Zone boscate 773,5 5,5 787,4 5,6 +
Zone caratterizzate da vegetazione arbustiva e/o 32 677,5 4,8 664,9 4,7 - erbacea
33 Zone aperte con vegetazione rada o assente 130,4 0,9 130,2 0,9 -
4 Zone umide 0,1 0 0,1 0 =
41 Zone umide interne 0,1 0 0,1 0 =
5 Acque continentali 176,8 1,3 168,9 1,2 -
51 Acque continentali 176,8 1,3 168,9 1,2 -
Tab. 6. Land use change (2003-2008). Source: Land use map, Regione Emilia-Romagna (1:25.000)
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2.3. Territorial infrastructures
2.3.1. Artificial water canals
Bologna is mainly located in an alluvial plain between the Reno river and its tributary Savena. The hydrography of Bologna is characterized by an artificial network of canals built in the past to provide water and hydropower to the city. The Reno canal comes from the same named river through the Chiusa di Casalecchio and run to the western part of the suburban area. The Savena canal comes from Savena stream and then flows to the eastern part. The two canals, reaching the historical centre, branch off to a complex and vast interlinked network of underground canals that drains urban rain water and the flow of small streams coming from nearby hills. the drainage the small streams water. Water flowing in such network is finally discharged into two main canals - the Navile and Savena canals - that leave Bologna urban area to be used for irrigation in the lowlands; remaining flow of Navile and Savena canals is pumped back to the Reno river several Km downstream.
In the urbanized area, some canals receive grey and black waters coming from combined sewer overflows and some other, due to a progressive urbanization, has been put underground becoming a part of the public sewer.
2.3.2. Transport networks
The public transport system of Bologna is made up of 43 urban lines and 15 suburban ones which extent to almost 461 km, 60 km of which are covered by 4 trolley bus lines. There are also 30 km of “protected” fast lanes, equal to 6,5% of total extension,.
The transportation system that support the so called “soft mobility” (pedestrian and cycling) is about 120 km, made up of 81 km of cycle paths and 12 km of natural cycling routes within green areas, 9 km of slow mobility roads (speed limit 30 km/h) and 10 km of pedestrian streets.
Figure 16 shows the map of cycle paths (marked in green) and of public transport fast lanes (marked in red) that insist in Bologna territory.
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Fig. 16. Cycle path and fast truck
2.3.3. Energy networks
The Bologna energy network extends to almost 90 km of aerial cables and 30 km of underground ones.
High-voltage power lines carry electric power to the main cabin which allocates it to final users through medium and low voltage.
The high-voltage system not only provides electric energy to civil and industrial users, but also to the railway system, both for people and freight transport.
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Fig. 17. Electric energy system
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3. HEAT WAVES AND HEAT ISLAND
3.1. Measurement campaigns and alerts
In order to study the distribution and magnitude of the heat island and bioclimatic discomfort in Bologna town, there were conducted two measurement campaigns during summer season, ones on 2001 and second on 2006. The results showed that within the urban area, the bioclimatic conditions are fairly uniform throughout the day, while they differ significantly during the night. Moreover, during the night the conditions are markedly worse in the urban area than those of the suburban and rural level.
The measurements showed that in the middle of the day the most uncomfortable bioclimatic conditions are found in rural areas with apparent temperature of about 1-2 °C higher, with respect to the urban reference station. The temperature of the hill (Sasso Marconi) is about 1°C warmer than those of the urban reference. The maximum temperatures are very close at all stations with differences within 1°C. The stations located in the plain of rural area showed values of minimum temperature of about 3- 4°C lower than those of urban station of reference. As regards the maximum values of relative humidity, this showed important differences: in the rural flat maximum relative humidity is about 25% more than at the urban reference station, the difference between the peri-urban and urban reference is 10% .
The campaign of 2001, that used 9 reference stations and a network of 21 thermometers, allowed us to draw the boundaries of urban heat island during summer at a certain date and its hourly evolution during day and night.
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Fig. 18 Heat Urban Island –temporal variability
The availability of data from this campaign as well as those obtained from modeling process allowed to construct a local early warning and alert system for heat waves for the Municipality of Bologna, addressed particularly to older people with a fragile situation, with health or social and economic problems. The service is based on a network of solidarity and on initiatives to raise awareness and support, to provide information, help to the distribution of water and fruit through the network of local services assured of voluntary associations, centers Social Services of the participating pharmacies and home care. The project is active from 15 June to 15 September each year and on 2013 reached 5,181 seniors.
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Fig. 19. Bulletin of alert for heat waves
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3.2. Distribution of urban green spaces and the most vulnerable population
The municipal area of Bologna is approximately 14,000 ha, and the public “green” consists of more than 750 areas that exceed 1,100 ha, representing approximately 9% of the municipal territory. The parks and gardens count together around 250, with a total area of 600 hectares, to which are added:
- the green of street and those of sports centers, with 110 hectares each of them;
- the green of school, one linked to other public buildings or settlements and various marginal areas , for a total of 170 ha;
- gardens that exceed 10 ha in area.
The parks and gardens are the most important equipment and the structure on which hinges the green areas of the city. The public green per capita, usable is about 20m2, while if we consider the other categories of green, the surface area available to each of Bologna rises to 30 m2 and Bologna ranks third among the major Italian cities, after Padua and Venice, in terms of green per capita. The tree heritage has about 100,000 trees, in parks and gardens and around 18,000 copies in the tree-lined road.
If we consider the overall availability of green, including both surfaces "green" - green urban, agricultural areas and vegetated areas not planted with trees (woods) - both areas shaded by the foliage of the trees, the average availability of green is more than 60 m2/inh, but with very different values within different sections of the census.
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Fig. 20. Bologna interactive map (Source: Comune di Bologna, http://www.comune.bologna.it/ambiente/servizi/6:20344/20345/)
Table 4 (Green by category)
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As could be noted the census tracts that include agricultural and hilly areas are characterized by absolute percentages of green and green per capita availability of generally high. In historical areas the availability of green is significantly lower, with a prevalence of sections where the percentage is between zero and 5% and the availability of green per inhabitant is less than 5 m2.
Table 5 (Green per resident)
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Table 6 (Green per cadastral section)
In an urban context of Bologna, the green if important from different point of view: health, hygiene and ecological functions: air purification, oxygen production, fixation of gases and airborne particulate abatement, reduction of noise pollution, heat regulating the microclimate of the city, etc.. It is therefore necessary to pay special attention to the distribution of public parks in the municipal area, in particular with regard to those areas of the city where there is a greater number of people considered "potentially" at risk, such as those over 65 and children under 4 years.
The population aged 65 and over, is mainly distributed in the most densely populated areas of the township, with a particular concentration in Savena (Area Mazzini) and Navile district, where there are census tracts with the highest number of elderly.
The population with less than 4 years is more evenly distributed throughout the territory, but it can be observed a prevalence of census tracts with a relatively high number of young children in the vicinity of the historical areas (eg Santo Stefano) and areas more distant compared to the historical center, particularly in the districts of Navile and Savena.
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Table 7-8 (Distribution of the population under 4 and over 65 years )
Particularly critical, from the point of view of the vulnerability of the population with respect to the heat islands, are the sections where the percentage of available green is low and at the same time the percentage of the population over 65 years old and less than 4 years is higher. The vulnerability of the population, should be seen on the basis of the per capita income (average value), available for each district: the old town, for example, and some parts of
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Savena district, are indeed characterized by a high percentage of the population over 65 years old and from a percentage of greenery per capita inferior to other neighborhoods, but are distinguished by an average income per capita higher than in other areas of the city, which significantly lowers the level of vulnerability. The level of vulnerability can be considered rather high in Navile District ( Area Bolognina ), San Donato and Borgo Panigale , which are characterized as the Districts with lower average incomes, and have an uneven distribution of green, although higher than in other Districts. In Tables 9 and 10 are represented the percentage of census tracts with green less than or equal to 5% and the percentage of the elderly population present.
Tavole 9-10 (Population under 4 e over 65 with green less than 5%)
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Urban green spaces land local ecological network Finally, it should consider the possible interactions between the development policies of urban green spaces and those related to local ecological network.
In Bologna area there are sites belonging to the European ecological network Natura 2000 (SIC-SPA), including a part of the Regional Park “Gessi Bolognesi”, Calanchi dell'Abbadessa, Golena San Vitale and Golena del Lippo.
The local ecological network has a strong duality between the foothills and the hills on one side and plain on the other area. The scope and elements of natural and environmental value of the foothill and hill are numerous and spread fairly evenly. The plain is, however, characterized by a marked poverty and fragmentation of natural habitats and a high concentration of elements of impact. The only significant exceptions are represented by the rivers, especially the most downstream portion of the river Rhine, where he is the only area included in the regional system of protected areas (Area of Ecological Riequillibrio San Vitale of Reno), and with a different weight and many limitations, some stretches of the river and canal Savena Abandoned Navile.
In urban and peri-urban areas there are even less open spaces, that can be considered as natural or semi-natural habitat matrix and become part of the local ecological
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network. Only in a few cases there is a certain continuity between some public and private green spaces: examples that stand out include a river Rhine and other rivers mentioned for the plain, to which are added traits of other courses such as minor Ghisiliera channel, the stream Ravone and especially in the eastern section of the township, the torrent Savena.
Fig. 21. Map of the ecological network of Bologna
3.3. Interaction between climate change, pollution, pollen and health
Numerous studies have emphasized the link between climate, air quality and the increase of pollen concentration. In the case of Bologna city, taking into account the
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special geometrical shape of the center of Bologna, which has a medieval urban structure with narrow streets and the presence of characteristic arcades (which prevent the replacement of the air masses), these contribute to the decreasing of diffusion of pollutants and generating a nearly stationary of concentrations. Air pollution plays a major role in the interaction between pollen and respiratory system, affecting the symptoms of allergies and accentuating the body's immune reaction. One of the pollutants more interested in these processes is the nitrogen dioxide (NO2), which in combination with sunlight and hydrocarbons, leads to the production of ozone.
The average concentration and maximum levels of ground-level ozone are foreseen to increase due to climate change, especially changes of temperatures and more sunlight, as it will have a stretch of the season with the presence of ozone. Ozone induces epithelial damage and inflammation in the upper airways and lower, and it is related to an increased risk of exacerbation of asthma in asthmatics
During the last five years, the ozone concentrations measured at the urban background station of Giardini Margherita were always detected above the limit of the law, with the exception of 2010. Both in 2011 and 2012 the number of days when ozone concentrations (measured as the maximum 8-hour moving average) exceeded 120 µg were above the limit value of 25, both in urban and suburbs area.
Fig. 22. Number of days with concentration of ozone greater than 120µg (moving average computed each 8 hours)
In order to measure the concentrations of pollen in the atmosphere, since 1998 in ARPA operates a regional monitoring and forecasting of allergenic pollens (http://www.arpa.emr.it/pollini/default.asp), aimed to provide information to public health and citizens.
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On the other hand the changes in climate that appears in the last decades such as: global warming, changing rainfall patterns, the increase in extreme events such as drought, influence the production and dispersal of pollen, which is linked to meteorological factors such as temperature, precipitation and wind . For example, warmer temperatures and the extreme values , together with an increase of carbon dioxide, can push the plants to an early and prolonged growing season, with a significantly higher pollen production.
The positive trend of temperature will also reduce the biodiversity, affecting the growth of plants and encouraging the spread of new invasive species, which gradually replace native species. The loss of biodiversity, and the presence of new species could change the type of allergenic plant and the presence of pollen in the atmosphere. There is an increasing trend in the annual amount of pollen in the air, shown at a continental scale for many species, and is more pronounced in urban areas compared to rural or semi-rural areas. It is important to underlay also the interaction between the heat waves and pollinosis. In cities, in particular, the consequences are becoming more evident due to overheating of the air and of the presence of dust and pollutants.
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Fig. 23. Timetable of the concentration of airborne allergenic pollen and spores. Bologna station, the reference period 1999-2012
3.4. Climate change, new pests and health
Bologna is one of the first sites in the Emilia -Romagna region in which it was detected the Asian tiger mosquito (Aedes albopictus), accidentally introduced in Italy and Europe in the early 90s . The mosquito can transmit several arboviruses among which the most dangerous to humans are the dengue and chikungunia. The transmission of disease by the carrier are on the rise and in 2009 were diagnosed in Europe in 1485
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imported cases of dengue fever. The Emilia -Romagna region, as a result of the epidemic caused by the chikungunya virus in 2007, has launched a " Regional Plan for the fight against the tiger mosquito and prevention of chikungunya and dengue", in which you have activated a surveillance network. The fight against the tiger mosquito is based on a regional protocol adopted at the municipal level, valid from April to October, during the presence of the Asian tiger mosquito, which involves fighting activities in the public and specific sanctions in case of non- private areas of pest control. The Municipality of Bologna is active in dealing with larvicides manhole covers, gully tops and all potential standing water in public areas, and in informing the citizens to make it aware of its strategic role in the fight against the tiger mosquito. A telephone number is made available to citizens to gather information and provide tips and advice. There will also be “adulticide” only in unusual cases and cases of emergency as a result of diseases transmitted by the carrier. Recent studies of the urban area of Bologna, carried out by the team of experts of the CAA " Giorgio Nicoli ," have shown that the distribution and density of Aedes albopictus may be favored by environmental variables on a local scale, such as vegetation, land use, condition of buildings, number and quality of the manholes.
Fig. 24. Distribution of ovitrappole in the Municipality of Bologna. Survey campaign of 2009 and spatial analysis (logistic regression analysis) in red areas with a density higher than the average in green and those with a lower density
A study based on data collected in the urban area of Bologna showed that the NDVI (Normalized Difference Vegetation Index) can be a good variable for the creation of maps of the distribution of the tiger mosquito especially in the month of August. The maps thus created can guide future operations of vector control by focusing on the most suitable habitat for the tiger mosquito and thus help the preventive measures. The Regional Department of Health and the CAA "G. Nicoli "have carried out several
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studies on epidemiological models in order to define future scenarios at the urban level of infestation of Aedes albopictus and the risk of spread of dengue and chikungunya also in relation to climate change.
Fig. 25 High probability of the presence of the tiger mosquito in the month of August. The graduated symbols indicate the percentiles of the density of eggs computed over the season monitoring
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4. WATER SYSTEM AND HYDROGEOLOGICAL RISK
4.1. Water System, Soil Drainage and Water Holding Capacity
4.1.1. Surface water system
Reno river, Savena and Lavino torrents are the most significant basins in the municipal area; Aposa and Ravone torrents are to be mentioned as well, thought they are hilly brooks with very little springs and they are fed almost exclusively from direct runoff of rainfall. The Reno river crosses many regions; in the Bologna area its flow is irregular and directly connected to the withdrawals and releases from upstream storage basins, especially in the summer period. The Savena and Lavino basins are not provided with upstream storage systems and they are almost totally dry during the summer. The hilly torrents have no flow or very poor flow for most part of the year, with short runoff periods caused by rainfalls. Their natural basins have been preserved in the hills, but have been almost totally or partially covered and partly transformed into public sewers in the built area of the city. The natural and artificial water networks are divided into four main systems, which are partially interconnected: Reno basin (left side) and Lavino basin (right side); Reno river network; “Navile – Savena abandoned” network Savena river network.
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Table 11 Hydrographic network
4.1.2. Waterproofing and drainage capacity
The development of the built up area caused the spread of soil sealing, which prevents permeability in case of rainfall events, alters the run-off coefficient and hydraulic soil capacity, and stresses the drainage system as well: pollution materials (as metals) on the seals surfaces are not properly drained and water pollution increases.
These phenomena occur mostly during particularly intense rainfall events, and are likely to increase due to the climate change.
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The hydrological response2 of the Municipality of Bologna is well represented in the following figure, which shows that more than 50% of the area is characterized by a poor and very poor response, particularly in the areas where seals surfaces prevail (even if they are dotted with areas with an optimal response such as green spaces ad trees); in the 38,8% of the area the response is up to the average, in the 16,3% it is good and in the 10,9% it is optimal. This latter percentage refers mostly to the hilly area.
Fig. 27 Percentage Analysis hydrological response
2 The analysis was conducted using as a base the regional land use map (1:25.000 scale) and more detailed informations concerning the distribution on trees, hedges and rows.
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Table12 (Hydrologic Response)
4.2. Hydrogeological risk
4.2.1. Surface Flood risk areas
In the Eighteenth Century Reno's floodplain had a maximum width of 1,05 Km, while at the end of the same century it had a width of 0,85 Km. At present the width is only just over 0,5 Km, considering the area included among the embankments. According to the data provided by the Reno Basin Authority, in the Twentieth Century occurred 13 relevant floods: 3 in the Thirties, 2 in the Forties, 3 in the Fifties, 2 in the Sixties and 3 in the last decade. The floods were recorded in Casalecchio (a town South-West Bologna), the location of the Reno river lock.
Considering the monthly distribution of the floods occurred in the last century, most of them were observed in November (24), followed by December (16), then January (15), February (13), March (9), October (9), April (6), June (5), September (2) and May (1); no cases were recorded in July and August.
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The Reno Basin Authority has identified areas of high probability of flooding (50-year flood) and flood boundaries for 200-year floods: the produced maps and cartograms were quoted in the Provincial Masterplan (PTCP) and represent the main reference for the city of Bologna. Inside the Municipality, some buildings are interested of flood risk, as they are located into the river basin (Via Bruto Giugno).
Fig. 26. Reno River: flood risks for buildings
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Fig. 27. Reno River: flood risk for buildings in case of 200-year flood
Regarding the minor hydrographic network, a focused research has been carried out, in order to identify the critical points of the drainage system in the high plain area.
Table13 (Hydraulic Risk depending on the type of buildings)
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4.2.2. Surface Landslide risk areas
The hilly area of Bologna can be divided in two well defined parts: the first one is located in the Northern area and it has a good ground stability. The second one is located in the Southern area and it has a higher degree of landslide susceptibility, since it is mostly composed of impermeable clays. It is easily eroded by rainwater, which flows out almost completely on its surface, and causes the spread of wide gullies. Landslides have been classified on the basis of their activity, in order to better plan the monitoring actions: Active landslides – the landslide is in motion or display signs of slow movements or adjustments, as a consequence of both morphological and climatic conditions. Dormant landslides – the soil shows an apparent stability, but shows little signs of movements which can lead to an active landslide (the so called “reactivated landslide”). There are several types of landslides and other downhill mass movements. The most common ones seen in Bologna include creep, slides, slumps and “mixed” landslides; they all have a little extension and they mostly affect the slopes mantled with debris (which usually do not exceed 3-4 meters thick).
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In the hilly area 449 active landslides have been identified: they cover an area of about 2,65 Km2; the identified dormant landslides are 270 and they cover an area of about 4,05 Km2. The overall landslide extension is about 6,70 Km2, that means the 18.4% of the hilly area of the city. Landslide risk regards not only the hilly part of the city, but also other areas of about 4,23 Km2, composed by slope sediments, badlands and woods (see City Masterplan - Region Profile).
Table 14 (Areas with hydrogeological risk)
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4.3. Surface water quality and water treatment
4.3.1. Surface water quality
The surface water quality in the Reno basin has stationary values for the years 2000 – 2009. The quality worsen from the source to the plain, downwarding from a good quality standard to a poor or very bad one. The monitoring techniques have been improving since 2009; they are regulated by the D.Lgs. n.152/99 and D.Lgs. n. 152/06, which adopt the European Directive n. 2000/60/CE. The laws redifined the monitoring techniques and the classification, as well as the monitoring networks and the related work programs. At the time, data from 2009 are the latest available: the chart 8 show the situation in the Bologna area.
Stazione di monitoraggio LIM 2007 IBE 2007 SECA 2007 SACA 2007 Casalecchio chiusura bacino montano 280 6 classe 3 Sufficiente Castelmaggiore a valle scarico Bolo 60 classe 4 Scadente Caselle chiusura bacino 125 4 classe 4 Scadente LIM 2008 IBE 2008 SECA 2008 SACA 2008 Casalecchio chiusura bacino montano 230 7 classe 3 Sufficiente Castelmaggiore a valle scarico Bolo 45 classe 5 Pessimo Caselle chiusura bacino 80 (4/5) classe 4 Scadente LIM 2009 IBE 2009 SECA 2009 SACA 2009 Casalecchio chiusura bacino montano 300 (8/9) classe 2 classe 2 Castelmaggiore a valle scarico Bolo 70 classe 4 classe 4 Caselle chiusura bacino 150 (4/5) classe 4 classe 4 Tab. 8. Surface water quality
The quality goals set in the regional Water Management Plan (2005) envisage the achievement of a good status throughout the Reno basin by 2016: this goal, even in the absence of updated data, appears unlikely to be reached. In 2011 – 2012 ARPA carried out an integrative monitoring programme for the Navile Canal; the programme was extended also to the year 2013. The following table shows the average values of the chemical and microbiological water macrodescriptors; the values are compared with 2 monitoring stations of the Reno basin, the first one located upstream the urban area and second one located downstream.
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The chart shows the Navile Canal has still extremely critical pollution conditions, also upstream from the water purifier's sewer (IDAR) exhaust; the Reno River shows a dramatic organic loading rate as well.
Biennio 2011 - Azoto Azoto BOD5 COD Fosforo E. coli 100- 2012 Nitrico Ammoniacale O2 mg/l O2 totale UFC/100 Oss. N mg/L N mg/L mg/l P mg/l ml Disciolto O2 % F. Reno Casalecchio 0,25 0,03 3 7 0,05 325 20 20C.le Navile 0,2 7,8 7 29 0,8 10300 71 Ponte della Bionda Corticella C.le Navile Castel 1 8,4 11 36 1,57 20000 54 Maggiore Bentivoglio 1,6 7,8 4 29 1,55 1850 72 C.le Navile Castel 0,7 3,5 11 24 1,87 1395 55 Malalbergo F. Reno S. Maria 0,9 0,39 6 11 0,32 240 26 Codifiume Table 9. Navile Canal: Chemical and biological composition
4.3.2. Sewage system
Bologna has a mixed sewage system (the percentage of separate network is less than 3%) in which the rainwater is collected and drained together with domestic and industrial sewage; this old system contemporary to the historical development of the city. The network is about 800 km long and it also receives wastewater from eight neighboring municipalities: it was partly built with bricks at the end of Nineteenth Century. Nowadays, many sections are in a poor conservation condition. Significant is also the canal system of the city, created and modified over the centuries: today, about 30 km of the canals convey wastewater to the sewage system.
The sewage system designed for the collection of rainwater is about 1300 km long and has about 70,000 catch basins (trap-doors, basement windows, grills) and 6 water- lifting devices. The collected water is mostly collected into the mixed sewage system. This network for water collection is mainly located on the foothills, it exploits part of the natural and artificial basins to convey urban wastewater into the public sewage system, bringing also significant percentages of rainfall into the purification system.
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The current municipal sewage network system is able to collect all urban wastewater, with a degree of coverage very close to 100%.
The issues relating to rainwater harvesting are both quantitative, ie hydraulic, both qualitative; they mostly depend on the quality and performance of the receiving devices. The sewer system has more than 250 spillways which relieve the hydraulic network in case of rainfall and direct it to the surface water courses (especially towards the main waterways: Reno, Savena, Navile, etc.): this system avoids the network congestion, but contributes to increase the flow and the flood risk downstream (the Navile, for example, tends to overflow downstream of the City of Bologna), and also to increase the water pollution (where the waters already have a low quality). Among the critical points identified, there is the stretch “Diversion Canal Navile Savena”, with 7 spillways, which discharges into the canal about 256 t/year of BOD, about 12% of the total load.
Table 15 (The sewer system
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In order to limit the impact of quality / quantity of the waters discharged by the spillways to the surface waterways, the national legislation (L.36/1994) provides since several years for the separation sewage from stormwater in all new urban areas, but this law has not been applied for a long time (many settlements built after 1994 still had mixed networks). For the existing networks, the separation is often not technically or economically feasible, therefore the Waters' Protection Plan of the Emilia-Romagna region provides for the use of "first flush tanks" that allow to contain the first waters coming from the spillways - that are the most polluted - and then to return them back to the sewer system, in order to send these waters to the purifier plant. The rules prescribe the construction – by 2016 - of tanks able to shoot down the 50% of the load coming from the spillways of the urban areas with over 20,000 inhabitants, and to shoot down the 25% of the load from spillways located in urban areas with a number of inhabitants between 10,000 and 20,000. To reduce the flood risk, it is provided for the construction of detention basins, with volumes that allow to contain the second rains, which, being less polluted, will not be sent back into the sewer system, but they will be slowly piped into the waterways, at the end of the meteorological event, in order to avoid to affect the formation of floods downstream In Bologna, the adoption of stormwater management systems has been applied since many years to all the new urbanization areas. These systems are based on rain water and detention basins and on the construction of separate sewer plants, located in different areas of intervention, resulting in the realization of numerous small containment / treatment systems. For example, with regard to detention basins, each new urbanization department shall provide for the construction of a system to laminate rainwater according to the parameters set by the Basin Authority. These lamination systems should discharge in the clean waters networks, but if they are absent in the area, it is allowed to discharge them into the mixed drainage system. The most innovative solutions for the management of the rains in urban areas, universally known by the term SUDS (Sustainable Urban Drainage Systems) are not very common in the Municipality of Bologna, although some recent settlements use innovative solutions such as green roofs and draining park places.
4.3.3. IDAR Purification plant
IDAR purification plant is the third sewage treatment plant in Italy for potential (900,000 AE); it receives wastewater from the Municipality of Bologna and from eight
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neighboring municipalities of approximately 500,000 AE. Every year about 50.000.000 m3 wastewater are treated in the system. The performance of the system is high, the refluent water has a good quality and it usually meets the range set by the D.Lgs. n. 152/06. Due to the high the volume of incoming waters to the plant, adequate storage systems and a treatment plant for first rain waste water have been set. Nevertheless, the conditions and the effectiveness of the purification plant are worsened by relevant volumes of surface water coming into the plant. In fact, a too frequent activation of the “bypass” option has been noticed even in case of not relevant incoming flows. In case of heavy rainfall (between 10 and 20mm), the purifying capacity of the system decreases dramatically to 60% (between 35% and 80%). It also appears that the load of BOD and COD delivered to the treatment plant is heavily reduced in case of precipitation (-35% with weak rainfall and - 70% with heavy rainfall): the remainder which does not reach the treatment plant is directly delivered through the spillways to the surface water system, without any kind of purification treatment. The Water Masterplan considers the design and realization of a first rain barrel upstream from the purification plant, but currently no funds have been provided (and the intervention has been delayed after 2016). Its implementation would improve the discharge into the Navile Canal. However, another the construction of another first rain barrel is planned in the area where the new headquarters of the Municipality of Bologna are located : such intervention would improve the situation in the Navile Canal as well.
4.4. Water use and water scarcity
4.4.1. IDAR Water taking and water consumption
4.4.2. Water taking
Three groundwater wells are located in the suburban area of Bologna (Ducati, Tiro a Segno and Fossolo ); two other wells are located in a outer area (San Vitale and Mirandola). From the wells are extracted overall about 50.000.000 m3/year . Surface water is taken mainly from Val di Setta (Setta Valley), able to provide an average of 35-40.000.000 m3/year .
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The overall supply needs are significantly different during the year, from 8.700.000 m3 in July to 6.600.000 m3 in February. The town waterworks tends to exhaust the available water coming from Val di Setta: the released water volumes are 4.000.000 m3 per month in winter and spring, dropping to less than 2.000.000 m3 in August. Water takings from groundwater wells located in Fossolo and Mirandola follows a regular monthly trend, while the other ones (Tiro a Segno, Ducati and San Vitale) are regulated upon the availability of the Val di Setta supplies, with 2-3.000.000 m3 in winter and and over 4.000.000 m3 in summer.
4.4.3. Water consumption
The waterworks system is managed by HERA SpA and serves about 760.000 citizens. The yearly water taking is about 94.000.000 m3, while the yearly invoiced amount is about 71.000.000 m3 (which means the 75% of the total water taking). The water consumption for the Bologna area is slightly less than 50% of the yearly invoiced amount.
Water taking in 2012 was 43.200.000 m3, the invoiced amount was 31.700.000 m3 (73% of the total water taking), which means an average consumption of 225 l/ per capita/day. This value shows a decreasing trend over the past 10 years and it is 15% lower than the one in 2003. About 70% of water consumption (22.100.000 m3) comes from civil uses (down to 157 l/per capita/day in 2012, 9% less than in 2009), while 22% is related to commercial and industrial uses (7.100.000 m3).
Consumi idrici procapite totali
270 266 261 260 255 254 250 250 242 238 240
229 227 230 225
Litri/abitante/giorno 220
210
200 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Anni
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Consumo domestico procapite
190 185 184 185 179 179 180 177 177
175 172 170 165 161 160 160 157
155 Litri/abitante/giorno 150
145 140 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Anni
Figure 30-31. Water consumption per capita
4.5. Water use in agriculture
Regarding the whole Bologna Province, the agricultural water use is the most relevant one, covering the 53% of the total water uses; civil use is 33% and industrial use is 14%.
The agricultural sector exploits about 72.000.000 m3/year, against about the double amount of water taken. Water taking comes mainly from surface water (about 120.000.000 m3/year ); 70.000.000 m3 of water is taken from the Po river and about 20.000.000 m3 of water is taken from groundwater supplies. A research lead by ARPA (Regional Agency for Environmental Protection) on the weather conditions in the year 2012 estimated a potential water irrigation need in 3.840.000 m3. Data about water taking from Land Reclamation Authorities, water works and private wells from agricultural uses are based on these values: the result is 1.700.000 m3:
Water takings from groundwater well authorized by Emilia-Romagna Region (Technical Serice for Reno Basin) in 2012: 230 424 m3 Water takings from private well in 2012: 503 740 m3 Water takings provided by the Casalecchio Lock Land Reclamation Authority in 2012: 520,000 m3 Water takings provided by the Reno Land Reclamation Authority in 2012: 350,000 m3 Water takings provided by HERA (waterwells) in 2012: 115 069 m3
Water taking for agricultural use in the Municipality area is between 2% and 5% of the overall takings in the provincial area. It is worth mentioning that water consumption
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for agriculture in the Municipality area, although it is a small part of the annual consumption, converges in the summer period, which is the most critical one due to the scarcity of the resource and the simultaneous demand for civil and industrial use. for the limited flow surface and the simultaneous growth in demand for civil (in part also due to irrigation of gardens, private and partly public , using resources from the civil aqueduct). Civil use increases also because of the increasing demand for irrigation of public and private spaces. The impact of water consumption for irrigation is regarded as relevant on the reduction of the rate of river flows and groundwater supplies.
4.5.1. IDAR Water use in industry
The water use for industries located in the city are estimated in around 5.000.000 m3; about 2.300.000 m3 of them come from the waterwells (7% of the overall amount released by waterwells).
The companies with a relevant water demand potentially belong to the manufacturing sector . According to the 2011 census, 1.766 manufacturing companies employing 18.104 workers are located in the Municipality. The manufactoring sector is mainly composed by clothing industries (217) and by food industries (211), and employ 16% of workers. Metalworking industries are also relevant (180), followed by press and machinery industries. The latter employs 19% of workers.
In the municipal area are located 5 large companies employing more than 500 people, 14 companies employing a range of 100-500 people and 13 companies employing a range of 50-99 people.
Attività manifatturiere nel Comune di Bologna (anno impre addet 50-99 100- >500 2011) se ti addet 500 addet ti addet ti ti
10: industrie alimentari 211 2.869 2 3 1
13: industrie tessili 38 144
14: confezione di articoli di abbigliamento, articoli in 217 1.910 2 1 1 pelle e pelliccia
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15: fabbricazione di articoli in pelle e simili 62 476 1
16: industria del legno e dei prodotti in legno e sughero 89 197 (esclusi i mobili)
17: fabbricazione di carta e di prodotti di carta 5 118
18: stampa e riproduzione di supporti registrati 126 704 2
19: fabbricazione di coke e prodotti derivanti dalla 1 24 raffinazione del petrolio
20: fabbricazione di prodotti chimici 27 855 2 2
21: fabbricazione di prodotti farmaceutici di base e di 2 650 1 preparati farmaceutici
22: fabbricazione di articoli in gomma e materie 24 172 plastiche
23: fabbricazione di altri prodotti della lavorazione di 45 148 minerali non metalliferi
24: metallurgia 10 57
25: fabbricazione di prodotti in metallo (esclusi 180 1.233 1 1 macchinari e attrezzature)
26: fabbricazione di computer e prodotti di elettronica e 42 531 1 ottica….
27: fabbricazione di apparecchiature elettriche….. 31 102
28: fabbricazione di macchinari ed apparecchiature nca 114 3.455 3 4 1
29: fabbricazione di autoveicoli, rimorchi e semirimorchi 14 385 1 1
30: fabbricazione di altri mezzi di trasporto 7 1.000 1
31: fabbricazione di mobili 35 116
32: altre industrie manifatturiere 305 901
33: riparazione, manutenzione ed installazione di 181 2.057 1 macchine ed apparecchiature
Attività manifatturiere 1.766 18.10 13 14 5 4
Table 11 . Census of industrial manufacturing (2011)
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A research made by ARPA in 2008 estimated that water taking in the muninicipal area is 3.500.000 m3 for the most water-demanding industries, and 4.700.000 m3 in the neighbouring areas. 20% of the water use (700.000 m3) is related to sanitary uses. Drinking water needs for the industry sector is estimated in m3 , 1.100.000 m3 of purified and reused water (with further specific treatments) and 600.000 m3 of partially drinking water with some higher reference ranges (eg . nitrates, bacteria) 22 further companies have been also monitored, as their water takings come from the city waterworks and are higher than 10.000 m3/year (1.500.000 m3): among them are and important dairy company, which uses 1.500.000 m3 water per year (90% taken from a groundwater well), and 8 other companies which take from private wells around the 23% of the remaining 500.000 m3.
4.5.2. Water losses
Water losses are about the 25% of non-revenue losses, whereas the real losses decreased increased from 17% in 2006 to 15 % in 2010 (in line with the target set by the Water Masterplan).
The Plan for losses reduction drew up by HERA SpA (2008) works mainly on the hydraulic modeling for supply and distribution networks. Pressure reducing valves are going to be installed and calibrated, in order to lower gradually the pressure in the distribution network of the municipal area. Broken parts causing leaks in the the water network, which have been reported or discovered during monitoring activities, are currently registered in databases and georeferred.
Monitoring actions aiming to find hidden losses are carried out every year and cover approximately the 12% of the whole network. Water losses in the provincial irrigation network are extremely high, about the 59% , which is above the regional average (48%).
4.5.3. Agreements for water use in case of drought
The water network Navile-Savena Abbandonato is a diversion of the Reno river, starting upstream HERA's water intake structures located on the river.
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The water network is fed by the Reno river through the Casalecchio Lock, and it feds – in turn – the neighbouring areas. The Navile-Savena Abbandonato system is made by channels and hydraulic structures belonging to the Casalecchio Lock Land Reclamation Authority; the water is used for agricultural needs, flowing through the Ghisiliera and Reno75 Canals, and to produce electricity in the power stations Canonica and Cavaticcio. Furthermore, these channels and hydraulic structures feed the urban drainage system, both for sanitary, historical and cultural purposes.
The system leads then water downstream to the Navile Canal. In May 2012, the Emilia-Romagna Region decided to better regulate the water management and its different uses in case of drought. It was noticed that in the mentioned area further water takings in drought periods can be allowed for a short time, as a derogation to the ranges set for the minimum average water downflow. The priority is to ensure the availability of drinking water, then to ensure the regulated range of water quality in ricers and canals (such as Reno and Navile), and finally to ensure other public uses.
A Working Group was set to monitor the water taking procedures; it also elaborated further technical proposals aiming to integrate the available water supply in the hydraulic system during the summer period and other periods with a high drought risk. The proposals are listed under:
1) activate a storage system called “Reno vivo”, providing all the structures needed for its working; 2) reactivate the storage system located upstream the Casalecchio Lock; because of the lack of maintenance, it has been buried aver the years, and no regulation of incoming water flow is possible; 3) work on a water infrastructure in order to realize a deviation from Canal Emiliano- Romagnolo to Ghisiliera Canal, stressed by water taking for agriculture; 4) increase the water releases from the Suviana storage system (mainly used for energy production). It is deemed it necessary to double them, passing from 8 to 16.000.000 m3 (of which 3.000.000 for irrigation and sanitary uses and 5.000.000 for civil uses). This request is also due to the decreasing water need for energy production, replaced by the use of solar and photovoltaic systems; 5) research and design an appropriate gauging system and a remote monitoring tool in order to better control for water flows and nodal points of the water system.
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4.5.4. Final assessment, challenges, future scenarios
To sum up what described above, the water use and taking in the municipal area can be summarized as follows:
Waterworks: 35.000.000 m3 (of which 2.300.000 m3 for industrial use); Industry: 2.800.000 m3 (from private wells); Agriculture: 1.700.000 to 3.800.000 m3
Regarding the water supply security, the waterworks system shows two main weaknesses: the lack of storage systems and of alternative supply sources to the acquifer and the Setta River. These lacks have always been compensated with an increasing water taking from groundwater reserves, which led to an overexploitation of the resource. Recently, water-taking from groundwater reserves has been partially limited, as agreements against payment have been signed with the energy company ENEL, which allow to take water from the storage basins located in the Apennines. The Water Conservation Plan (2008) points out an excessive taking of groundwater (12.000.000 m3 year), which has increased subsidence phenomena. Regarding other water sources, the Plan estimates that the Setta River can be exploited till 44.000.000 m3/year. In the period 1997-2006 water coming from that source and make drinkable by the Setta Water Plant is estimated in 38.000.000 m3/year.
This value will be reducted up to 27-31.000.000 m3/year, in order to conform it to the regulations about the Minimum Water Flow; its range value was set to maintain an higher river inflow and to assure an higher water quality. Regarding the climate projections, water taking should be further reduced to 22.000.000 m3/year, in order to maintain the quality standards which are going to worsen in the more and more frequent drought periods.
4.6. Groundwater: Qualitative and quantitative status
The aquifers located in the Bologna plain play a leading role in the management of groundwater resources; they feed three main urban pumping plants (Borgo Panigale, Tiro a Segno and San Vitale, see § 4.1.1), all located on the Reno cone. Other pumping plants placed in the Savena and Idice cones (Fossolo and Mirandola) contribute to the water taking for civil use as well. All these plants are run by HERA SpA, and they use about half of the groundwater resource.
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Even if the quantitative classification (SCAS) does not show an over-exploitation of the groundwater resource for every single well belonging to the Reno-Lavino cone and its alluvial plain, relevant criticalities have been noticed for the groundwater-related subsidence. On the contrary, in the Savena-Idice cones the over-exploitation of the groundwater resource is directly matched with subsidence phenomena. The piezometric depression in the Reno cone is about 50-55 m depth from the ground level, and it covers neighbouring areas and cones within a 20-kilometre radius. This phenomenon has a dramatic influence on the water quality, as the depression bring pollutants to deeper and deeper areas, and it is directly related to the groundwater takings. Subsidence phenomena started in '50s to the '70s, then a piezometric stabilization followed. Currently the piezometric conditions are improving in the Reno cone, while the Savena cone still show critical conditions without any signs of improvement.
Figure 32 . Quality status of groundwater (Source: EPA)
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Figure 33 . Quality status of groundwater (Source: EPA)
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5. MAIN RESILIENCE FACTORS
The territorial analysis has allowed to find, beyond critical elements, some of the resilience factors which already reached positive results in increasing the local resilience. Below are listed some local best practice which can be considered as a starting point for future planning of resilience measures to climate changes.
5.1. New building
The Bologna Urban Building Rule
The Bologna Urban Building Rule (RUE) predicts, as a specific qualification for all building transformations (Art. 55), the mandatory commitment to create significant detention volumes (500 m3 per each sealed hectare) which allows to improve the overall drainage capacity of the urban area. The RUE also considers the necessity to reuse rainwater avoiding to deliver them into the sewer. Raining waters’ local treatment and storage have been also predicted before delivering them to the sewer.
5.2. Saving and management of water resource
The Casalecchio di Reno “Steering Committee”
In 2012 The Emilia Romagna Region established a Steering Committee with the participation of the different managing authorities of the Reno hydraulic system, having the task of managing the different specific needs which may appear with the changing availability of water resources. The Steering Committee defined an operative technical team that immediately started its activity in order to experiment the efficiency of the water flow regulation scheme and the releases in the Reno hydrological system, reducing the effects of the Reno basin’s water crisis.
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Reducing civil water consumption
The city of Bologna, together with the Province and the local utility Hera, has been committed for many years in reducing leaks and civil water consumption strategy which allow to reach a reduction trend of water withdraw for civil use. In particular, the Municipality has developed, since 2009, a water saving environmental education project that has been able to link, successfully, concrete water savings interventions with educational and communication campaign abut a new water culture. In particular, the project regards the domestic water consumption, which corresponds to 70% of total drinkable water consumption. In order to obtain a sustainable use of the resource, it is crucial to reduce, at the regional level, water uses for domestic, industrial and agricultural needs. Domestic consumption, according to the PTA (Water protection Plan - Piano di Tutela delle Acque) recommendations, has to be reduced more than 15% by the next ten years, until it will reach the target value of 150 litres per inhabitants per day. An awareness campaign oriented towards citizens, schools and local stakeholders, it is necessary to give good advices for a correct and controlled use of this common resource.
5.3. Stream requalification
Reduction of water draining interventions
The Piano d’Ambito (Urban Water plan) of Bologna Province envisages different measures aimed at the reduction of pollution load coming from civil uses and released in the Bologna water channels. These measures regards both the progressive removal of all sources of sewage still discharging in surface water, and the reduction of polluted waters coming from combined sewer overflow (CSO). In particular it is planned the realization of a large rainwater detention tank at the entrance of the urban wastewater treatment plant (financing postponed over 2016) and of another rainwater detention tank in the “Bolognina” area: both the envisaged instalments will reduce pollution load discharged into the Navile canal through CSOs improving its environmental conditions.
The “Lungo Navile” project
This project involves a series of measures, some of them already realized, focused on the usability of the main water channel of the local system (Reno Canal/Navile Canal)
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and includes other waterside cities: Casalecchio, Bologna and Castelmaggiore. The importance of this intervention is its capacity of building a relationship between population and water channel, a very important relationship gradually decreased due to the loss of water quality. The project also offers some opportunities in structural terms: even though most of the measures are focused on the usability , other interventions could contribute to increase the resilience of the channel through greening measures and the creation of detention areas (see the next two critical situations).
The Lungo Reno Park: an opportunity for natural process and overflow water detention systems
The area across the Reno River is today a mosaic of green spaces, some of them accessible and regularly used, some others less accessible or in decay conditions. The Reno Park project, a metropolitan river park (potentially the biggest of the city) aims at re-assembling the landscape of these green spaces, improving the overall permeability, thanks to: the redefinition and improvement of paths network; a new signage facilitating the orienteering and the enjoyment of places; the creation of real “open entrances” to the river conceived as meeting points between the city and the environment. In parallel to the renewal of these areas, a management and maintenance project– both naturalistic and related to sport centre, gardens and other equipped areas – has been conceived in collaboration with citizens and local associations. The adoption of a strategy for the natural treatment and storage of overflow water could find application in this area, due to the presence of many combined sewer overflows.
5.4. Increase and improvement of urban green areas
Bologna ecological network
The local ecological network was analysed in a preliminary study aimed to preserve biodiversity in natural and semi natural environments, which mainly exist in countryside and hillside of Bologna. There is a tight connection between principles and functional needs to the ecological network consolidation, and the draw of green system proposed for the city, highlighting the natural integration of themes strictly connected to the environmental sphere which characterize the complex green system of Bologna. The future development and reinforcement of the ecological network, particularly in those urban areas mainly affected by heat-islands, will allow the realization of greening interventions in order to improve the local micro-climate.
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The GAIA project
GAIA is the acronym of a LIFE project, co-financed by European Commission, aimed to increase green areas in Bologna city by planting new trees, in order to tackle the climate change effects, and to improve air and environmental quality. The initiative is sponsored by the Municipality of Bologna, as the coordinator of the project, with Cittalia – Fondazione Anci Ricerche, Impronta Etica, Istituto di Biometeorologia – CNR and Unindustria Bologna, and it is based on the subscription of public-private partnership between the Municipality and the local companies which decide to participate to the project offsetting the emissions coming out from their activities. The project, which lasts three years, will plant 3.000 trees within 2013 and will create an environmental governance system that could be reused in the future.
Villa Bernaroli
A city-country park, planned to preserve a part of valuable rural and agricultural territory in the western Bologna Plain, will grow all around the eighteenth-century Villa Bernaroli, on about 50 hectares of public property. The project has been conceived by a participated laboratory which involved, since 2006, Borgo Panigale neighbourhood, and many local cultural, social and agricultural associations. 45 hectares of agricultural areas will be subjected to a landscape renovation through the planting of hedges and rows of trees and, at the same time, leaving green areas dedicated to the free use of visitors.
5.5. Heat waves
Warning system and citizens assistance
The project “Heat waves prevention” defines actions to prevent risks for elders with high healthcare, social, economic and registry fragility, caused by summer high temperatures. This action has been oriented to the construction of a solidarity network for elders and their families through the contribution of voluntary associations, community centers and pharmacies which, together with the Social service housing assistance, supported the Municipality in the realization of dedicated information and communication campaigns. The project is realized by the Municipality of Bologna with the collaboration of Azienda Usl of Bologna, Arpa Emilia Romagna, Civil Protection, Social services for housing assistance to the districts and the operative coordination of Cup2000.
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6. CONCLUSIONS
Within this framework, climate changes will bring to the territory of Bologna a further worsening of pre-existent critical situation that, in some cases, have already been managed by policies both on the local and regional scale. The territory of Bologna shows a high level of artificial elements, especially in the northern Plain, not only due to the urban expansion of the last decades, but also to the historical modification of the surface hydrography (the first diversions from the Reno river through the “Chiusa di Casalecchio” date back to 1.000 ac). The most critical situations on which the attention should be focused in order to define a first action plan can be summarized as shown below.
6.1. Rising of summer temperature and heat-island
Improvement of green infrastructures to increase shading areas and evapotranspiration (greening). Identifying census sections with less availability of green areas and, at the same time, characterized by the presence of weak categories of citizens: the priority should be given to urban greening interventions coming from public initiatives in these areas, including demonstrative and awareness raising measures. Promoting structural and widespread greening interventions in transformation areas coming from private initiatives, using the existent building code and addressing the implementation of solutions with a higher “thermo regulative” impact (green roofs, arboreal species with high shading and evapotranspiration capacity, etc.). Promoting greening interventions having a multi-objective purpose supporting, at the same time, thermo regulative functions, urban biodiversity (ecological system) and the improvement of hydrological response. Promoting greening interventions linked to the redevelopment of cycling paths and public transportations. Improvement of the warning and assistance system for population
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6.2. Water crisis and drought
Reduction of water withdrawal, particularly during summer when dramatically emerges the conflict between the different uses of the resource. In the last years, there has been a decrease in domestic and non-domestic consumption. Promoting new water saving policies and campaigns in different sectors. Promoting for all urban transformation interventions the use of not conventional resources for undrinkable uses (collection of rainwater, treatment and reuse of grey water). Possible pilot actions with structural interventions related to big industrial or commercial consumption or in urban transformation areas. Deepening the theme of undrinkable uses (private and public irrigation, street washing, etc.) to verify the possibility of alternative supply.
6.3. Increase of intense weather events
Structural interventions aimed to improve the water storage capacity or to balance the surface flows Improvement of urban rainwater management by introducing Sustainable Urban Drainage Systems (SUDS), adapting public procurement procedures related to the sewage system Incentivizing the private interventions of urban transformation towards solutions which go beyond current regulations (the “water unchanging” duty) Taking into consideration the opportunity of public initiatives regarding some of the water critical situations already seen and assuming multi-objective solutions, which have effects on water quality too (ex. Water detention system integrated with combined sewed overflow natural techniques treatment) Non-structural interventions aimed to reduce the risk during intense weather events Integration and collaboration with the strategies finalized by the Civil Protection
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