Irrigation Sustainability in the Land Use/Soil System in South Italy: Results from a GIS Simplified Approach and Future Methodological Developments - Water and Agriculture: Sustainability, Markets and Policies - page 252

2.5 Data processing
Starting from SIGRIA database structure (Figure 7), the final evaluation process is
based on the intersection of the soil suitability and irrigated land use layers. A new layer,
with (per map unit) homogeneous data on soil suitability, land use, irrigation technique
and nominal crop water requirement per hectare, has been derived.

Figure 7. General scheme of relationships inside SIGRIA database

Land use
Soil

Water
sources
Irrigation
network

Water
availability

Irrigation Land
Capability

Climate Data

Areas with good suitability
for irrigation

Areas with not good suitability
for irrigation

The cumulative nominal CWR (m 3 = mc) per each homogeneous new map unit has
been derived from the hectares of each soil/land use/irrigation technique systems. The
real water crop requirements has been calculated from the IEff index. The cumulative real
crop water requirement (RCWR) has been obtained multiplying the cumulative nominal
crop water requirement (N CWR) by the IEff values (based on the criteria of soil
suitability per irrigation technique - see Table 8). The validation of this index is based on
the CWR calculation with SWAP, and then divided per the nominal CWR of the
5 Consortia test sites irrigated crops. These values has been correlated with the FAO
index. This procedure is shown in Figure 8. The gap between real and nominal water crop
requirements was defined for every map unit belonging to an irrigated area, defined a
delta of crop water requirement ( CWR R CWR N CWR

), which represent the
environmental effect due to the interaction of the irrigation techniques with the soil
characteristics.