Climate Change and the European Water Dimension - Agri ...

the main carrier of nutrients to groundwater.
Like nitrogen, phosphorous is one of the
most important mineral nutrients for
biological systems, but unlike nitrogen, is
found in sedimentary rocks and not in the
atmosphere (Leinweber et al., 2002).
Phosphate rocks are eroded resulting in a
phosphorous supply available to plants and
then to animals. Through plant or animal
tissue and faeces, phosphorous is returned
to water and soil in organic forms.
Phosphorous in the soil is dissolved in
water. Much phosphorous is lost at the
bottom of oceans. The main pathways
involved in the P cycle are similar to those
of the nitrogen cycle although the chemical,
physical and biological processes are
different. Manure, fertilizers and detergents
are the main factors that can influence the
phosphorous cycle. Therefore, the major
drivers are agriculture, livestock and
demography, whereas tile drainage, groundwater and runoff are the major pathways
to be considered when evaluating the effects of climate change.
Modeling the nutrient pathways in the Po Catchment
To estimate the effect of climate-changerelated
pressure factors on nutrient transport
pathways at catchment scale, a multicompartment
steady-state model was used
(Algieri et al., 2003; Pirrone et al., 2005).
Point and diffuse sources were considered in
assessing the relative contribution of different
nutrient transport pathways within the
catchment and to the CZ. Key socio-economic
indicators (Table-VI.C.3) were used in the
model, each sub-catchment was
characterized using GIS developed for the Po
catchment, and the final nutrient amount was
referred to the Pontelagoscuro outlet station
(the reference station). For each sub-basin,
and for the total catchment, the relative
contribution of each transport pathway was
estimated for both nitrogen and phosphorous
(see Table-VI.C.4). Our preliminary modelling
results show that a large contribution is from
diffuse sources, whereas WWTPs and urban
systems represent a significant pathway for
phosphorus load discharged to the Po
catchment and transported to the North
Adriatic CZ. Nitrogen is mostly generated by
agricultural activities (groundwater and tile
drainage accounting for more than 60%), but
WWTPs and urban systems represent a
185
Table-VI.C.3: Selected physiographic characteristics
and socio-economic indicators of Po Catchment (after
Pirrone et al., 2005).
General data
Drainage area (Italy 96%, Swiss and France 4%) 73,760 km 2
Length of the river 652 km
Minimum annual discharge (Pontelagoscuro) 275 m 3 /s
Maximum annual discharge (Pontelagoscuro) 10,300 m 3 /s
Average annual discharge (Pontelagoscuro) 1,510 m 3 /s
Average altitude 740 m a.s.l.
Delta area 380 km 2
Municipalities 3,251
Inhabitants 15,764,600
Density (min – max) 25 - 1,478 inhab./km²
Employed industry 3,171,000
Employed tertiary 2,791,000
Cultivated area 31,000 km 2
Cows 4,188,000 heads
Pigs 5,232,000 heads
Water resource uses
Area with irrigation use 1.5 x 10 4 km 2
Diverted flow rate 1,850 m 3 /s
Table-VI.C.4: Relative contributions of selected transport
pathways of nutrients loads in the Po basin assuming
the 2001 as reference year (Pirrone et al., 2005).
Pathway Nitrogen Phosphorous
t/y % t/y %
Atmospheric deposition 1350 0.5 61 0.6
Tile drainage 67212 25.6 1496 14.4
Groundwater 95830 36.4 862 8.3
Overland flow 4536 1.7 445 4.3
Erosion 958 0.4 835 8.0
WWTP 68992 26.2 3677 35.4
Urban systems 24091 9.2 3010 29.0
Total 262 969 10 386
Table-VI.C.5: Scenario for the Mediterranean system
(IPCC, 2001). Indicators of observed (2000) and
predicted (2025, 2050, 2100) changes.
Indicator 2000 2025 2050 2100
Global mean
temperature
(change from
1961-1990
average, °C)
Continental
precipitation
(change mm day -1 )
Heavy
precipitation
events
Frequency and
severity of
drought
Snow cover area
(since 1960)
Growing season
(days per decade)
0.2 0.4–1.1 0.8–2.6 1.4–5.8
0 -0.25
Increased Increased Increased
Increased Increased Increased
-10% Decreased Decreased Decreased
1 to 4 Lengthened Lengthened