Salvatore Barbagallo

A One-Layer Satellite Surface Energy Balance for Estimating Evapotranspiration Rates and Crop Water Stress Indexes

Daily evapotranspiration fluxes over the semi-arid Catania Plain area (Eastern Sicily, Italy) were evaluated using remotely sensed data from Landsat Thematic Mapper TM5 images. A one-source parameterization of the surface sensible heat flux exchange using satellite surface temperature has been used. The transfer of sensible and latent heat is described by aerodynamic resistance and surface resistance. Required model inputs are brightness, temperature, fractional vegetation cover or leaf area index, albedo, crop height, roughness lengths, net radiation, air temperature, air humidity and wind speed. The aerodynamic resistance (rah) is formulated on the basis of the Monin-Obukhov surface layer similarity theory and the surface resistance (rs) is evaluated from the energy balance equation. The instantaneous surface flux values were converted into evaporative fraction (EF) over the heterogeneous land surface to derive daily evapotranspiration values. Remote sensing-based assessments of crop water stress (CWSI) were also made in order to identify local irrigation requirements. Evapotranspiration data and crop coefficient values obtained from the approach were compared with: (i) data from the semi-empirical approach “Kc reflectance-based”, which integrates satellite data in the visible and NIR regions of the electromagnetic spectrum with ground-based measurements and (ii) surface energy flux measurements collected from a micrometeorological tower located in the experiment area. The expected variability associated with ET flux measurements suggests that the approach-derived surface fluxes were in acceptable agreement with the observations.

Analysis of treated wastewater reuse potential for irrigation in Sicily

In Mediterranean countries, water shortage is becoming a problem of high concern affecting the local economy, mostly based on agriculture. The problem is not only the scarcity of water in terms of average per capita, but the high cost to make water available at the right place, at the right time with the required quality. In these cases, an integrated approach for water resources management including wastewater is required. The management should also include treated wastewater (TWW) reclamation and reuse, especially for agricultural irrigation. In Italy, TWW reuse is regulated by a quite restrictive approach (Ministry Decree, M.D. 185/03), especially for some chemical compounds and microbiological parameters. The aim of the paper is the evaluation of TWW reuse potential in Sicily. A Geographic Information System (GIS) was built at regional level to quantify and locate the available TWW volumes. In particular, the characteristics of wastewater treatment plants (WWTPs) were integrated, through the GIS, with data on irrigation district areas. Moreover, in order to evaluate the Italian approach for reuse practice in agriculture, the water quality of different TWW effluents was analysed on the basis of both the Italian standards and the WHO guidelines.

Hydrologic Evaluation of a Mediterranean Watershed Using the SWAT Model with Multiple PET Estimation Methods

The Penman-Monteith (P-M) method suggested by the Food Agricultural Organization in irrigation and drainage paper 56 (FAO-56 P-M) was used in the Soil and Water Assessment Tools (SWAT) water balance simulation at the outlet of an experimental watershed in Sicily, Italy. A sensitivity analysis determined that the model was more sensitive to this potential evapotranspiration (PET) parameter than to the other six parameters impacting surface runoff in this small Mediterranean watershed. The FAO-56 P-M method was compared to the three existing SWAT PET methods from 1997 to 2003. The watersheds water balance was more realistically simulated by the FAO-56 P-M method than by the other PET methods. The traditional P-M method incorporated into SWAT overestimated total (surface and base flow) runoff volumes observed during the entire period by approximately 50%; however, total runoff volumes were underestimated by only 17% when the FAO-56 P-M method was used. The surface runoff simulation results using the FAO-56 P-M PET equation for calculating daily values was sufficient at the monthly time interval (Nash-Sutcliffe efficiency >0.75) during the calibration and validation periods. The incorporation of the FAO-56 P-M method has broadened the SWAT models applicability to watersheds that are in semi-arid environments with high-intensity, short-duration rainfall events.

Assessing environmental impacts of constructed wetland effluents for vegetable crop irrigation

ABSTRACT The objective of this study was to monitor and assess environmental impacts of reclaimed wastewater (RW), used for irrigation of vegetable crops, on soil, crop quality and irrigation equipment. During 2013, effluents of a horizontal sub-surface flow constructed treatment wetland (TW) system, used for tertiary treatment of sanitary wastewater from a small rural municipality located in Eastern Sicily (Italy), were reused by micro-irrigation techniques to irrigate vegetable crops. Monitoring programs, based on in situ and laboratory analyses were performed for assessing possible adverse effects on water-soil-plant systems caused by reclaimed wastewater reuse. In particular, experimental results evidenced that Escherichia coli content found in RW would not present a risk for rotavirus infection following WHO (2006) standards. Irrigated soil was characterized by a certain persistence of microbial contamination and among the studied vegetable crops, lettuce responds better, than zucchini and eggplants, to the irrigation with low quality water, evidencing a bettering of nutraceutical properties and production parameters.

Remote sensing of crop water requirements in orange orchards using high-spatial-resolution sensors

With the aim to derive crop water requirements (ETp) for an irrigated area covered by orange orchard in Sicily, Quick Bird and ASTER TERRA high resolution satellites data were used and compared with reference to their different spatial and spectral resolution. Satellites data allowed to improve the monitoring of canopy development in the irrigated area by identifying biophysical vegetation variable (LAI, albedo, vegetation indicators, etc); this information was successively used for the evaluation of maximum crop water needs by means of the well known Penman-Monteith equation. The paper results evidence the importance of very-high resolution sensors such as QuickBird in areas characterised by strong spatial heterogeneity. The algorithms applied to estimate the canopy parameters and the crop water requirements were applied by considering different levels of radiometric calibration of the satellite data, which produced marked differences in the final results.

DEFICIT IRRIGATION STRATEGIES: PRELIMINARY ASSESSMENT ON A SICILIAN YOUNG ORANGE ORCHARD

In Mediterranean regions the economical sustainability of fruit tree crops strictly depends on the limited availability of water resources. Deficit irrigation (DI) strategies are particularly suitable to optimize water resource, improve water use efficiency by reducing crop water requirements. In the study, DI strategies were adopted on a young orange orchard in Sicily (Southern Italy) and crop physiological features were monitored and analysed for possible negative effects. The orchard includes 300, 4-years old, trees, irrigated with drip and sub-drip irrigation systems. Four irrigation strategies (replicated 3 times), based on DI concepts, were adopted, each supplying different percentages (50, 75, 100%) of the irrigation requirement (IR). IR values were calculated via the Penman-Monteith model, by assuming a crop coefficient (Kc) of 0.45 typical for immature orchard, and correction coefficients accounting for the localized irrigation. Several physiological indices were measured during the trial, including Leaf Area Index, stem water potential, canopy temperature, and trunk diameter, among others. Preliminary observations, obtained during the two irrigation periods (2011-2012), evidenced slight variations of xylematic potential and stomata conductance among the monitored treatments. LAI, canopy volume and trunk circumference increases were quite similar among treatments. Accordingly, trees growth seems to sustain the imposed water restrictions, without significant stress symptoms on the analyzed physiological features.

DISCOVERING RESERVOIR MANAGEMENT CRITERIA: THE CASE STUDY OF POZZILLO RESERVOIR

Abstract An integrated Rough Set approach is proposed to discover the historical operation rules of irrigation purpose reservoirs. Operation rules are derived by expressing monthly releases as functions of reservoir stored volume, inflow and outflow. This is accomplished through the Rough Set approach and the use of performance indices able to recognize the effective rules used in water supply management. This approach represents a new mathematical tool quite different to classical fuzzy rule-based systems in the decision rules induction. Results show that the integrated Rough Set approach allows to individuate with acceptable reliability the real criteria used for the system management.

Experiences on Constructed Wetlands for Wastewater Treatment in Rural Areas: a Case-Study in Sicily

In Sicily many wastewater treatment plants (WWTPs) of small-medium communities are not in operation due to management problems and high O&M costs. Extensive treatment processes, such as lagooning and constructed wetlands (CWs), potentially represent a more appropriate and sustainable treatment solution in rural contexts, as in inland areas of Southern Italy where climatic conditions and land availability are favourable. The paper reports the first results of an investigation on a subsurface horizontal flow CW for the tertiary treatment (after a secondary treatment with trickling filter) of a rural community effluent of about 5,000 people located in Eastern Sicily. The system is designed to wastewater reuse for the irrigation of olive orchards covering about 150 ha. Since March 2001 a reed bed (for about 1,100 P.E.) is in operation with a flow rate of 1.75 L/s and a nominal detention time of about 2 days. The flow path from inlet to outlet is 78 m and the total area is 1,950 m2. Mean removal efficiencies ranged from 65% to 88% (TSS), 53% to 84% (BOD5), 62% to 80% (COD), 14% to 52% (TN), 15% to 45% (TP), 95% to 99.8% (faecal coliforms). The CW unit seems to operate efficiently since the starting of operation.