Performance analysis of pressurized irrigation systems operating on-demand using flow-driven simulation models

On-demand pressurized irrigation systems are designed to deliver water with the flow rate and pressure required by the farm irrigation systems, sprinkling or micro-irrigation, and respecting the time, duration and frequency decided by the farmers. Due to the variation in farm demand along the season and the day, a large spatial and temporal variability of flow regimes occurs in these systems, which may affect the performance of the farm systems and the yields of the irrigated crops. Therefore, there is a need to analyse those systems to identify and solve performance problems. In this research, two simulation models for the analysis of irrigation systems operating on-demand, ICARE and AKLA, are used and compared to assess the hydraulic performance of the irrigation network of the Lucefecit Irrigation System, in Southern Portugal. ICARE assesses the global performance of the irrigation system through the indexed characteristic curves, while AKLA provides for the identification of the relative pressure deficit and reliability at every hydrant. Both models adopt a flow-driven analysis approach, performing the analysis for multiple flow regimes. To support the hydraulic characterization of the system and for calibration of the steadystate hydraulic model, field measurements were performed at selected nodes of the network, including four hydrants. The analysis with ICARE does not provide for a sufficient identification of problems. In fact, poor performance is indicated when a few hydrants operate below the minimum pressure set at design. Differently, the analysis with AKLA, applied at the hydrant level, shows that the performance of the Lucefecit system is generally acceptable. AKLA identifies which hydrants operate below the required pressure and, therefore, allows to support any eventual related improvement. Results show that the performance of the system highly improved when changing the piezometric elevation from 260 to 265m a.s.l. However, this improvement is not sufficient because three hydrants still have high relative pressure deficit and low reliability. Solutions for those hydrants require increasing diameters of network pipes supplying them

A Stochastic Texture-based Approach for Evaluating Solute Travel Times to Groundwater at Regional Scale by Coupling GIS and Transfer Function

AbstractInterpreting and predicting the evolution of non-point source (NPS) pollution of soil and surface and subsurface water from agricultural chemicals and pathogens, as well as overexploitation of groundwater resources at regional scale are continuing challenges for natural scientists. The presence and build up of NPS pollutants may be harmful for both soil and groundwater resources. Accordingly, this study mainly aims to developing a regional-scale simulation methodology for groundwater vulnerability that use real soil profiles data. A stochastic approach will be applied to account for the effect of vertical heterogeneity on variability of solute transport in the vadose zone. The approach relies on available datasets and offers quantitative answers to soil and groundwater vulnerability to non-point source of chemicals at regional scale within a defined confidence interval. The study area is located in the Metaponto agricultural site, Basilicata Region-South Italy, covering approximately 12000 hectares. Chloride will be considered as a generic pollutant for simulation purposes. The methodology is based on three sequential steps: 1) designing and building of a spatial database containing environmental and physical information regarding the study area, 2) developing travel time distributions for specific textural sequences in the soil profile, coming from texture-based transfer functions, 3) final representation of results through digital mapping. Distributed output of soil pollutant leaching behavior, with corresponding statistical uncertainties, will be visualized in GIS maps. Of course, this regional-scale methodology may be extended to any specific pollutants for any soil, climatic and land use conditions

Random scenarios generation with minimun energy consumption model for sectoring optimization in pressurized irrigation networks using a simulated annealing approach

A pressurized irrigation network may operate in two ways, namely, on demand and organized under operating sectors. In the first case, the user decides when to irrigate, and the pumping station has to meet the discharge and pressure head requirements of the group of users that is demanding water at any time. In the second case, the operating hydrants at a given moment are previously established, which permits identification of scenarios related to lesser energy consumption. In this work, a new model was developed that identifies such scenarios. The optimization process is carried out by means of simulated annealing (SA). The model was applied to an example and the result obtained was compared with the same network operating on demand and sectorized using the criterion of hydrant elevation with respect to the pumping station. The scenario adopted for SA saved 11.8% and 15.5% in energy consumption compared with the two other scenarios, and decreased the installed power requirement by 38.3% and 21.6%, respectively.García Prats, A.; Guillem Picó, S.; Martínez Alzamora, F.; Jiménez Bello, MA. (2012). Random scenarios generation with minimun energy consumption model for sectoring optimization in pressurized irrigation networks using a simulated annealing approach. Journal of Irrigation and Drainage Engineering. 138(7):613-624. doi:10.1061/(ASCE)IR.1943-4774.0000452S613624138

Climate change and the performance of pressurized irrigation water distribution networks under mediterranean conditions: Impacts and adaptations

Numerous previous studies have modelled the impact of climate change on crop water requirements and hence future water resource needs for irrigated agriculture. Fewer have considered the impacts on the performance of irrigation systems and the required engineering and managerial adaptations. This study considers the impacts and adaptations for a typical pressurized pipe irrigation system. The dry years of the baseline period (1970-90) in the southern part of Italy are expected to become the average or even wet year by the 2050s, according to HadCM3 projections. Under these conditions, the large water distribution systems designed to satisfy the baseline dry years will fail unless appropriate engineering or managerial adaptations are made. The resilience of District 8 of the Sinistra Ofanto to the possible future increase in irrigation demand has been assessed. A stochastic weather generator was used to generate future weather under the IPCC A1 and B1 emissions scenarios, taking into consideration the outputs of the HadCM3 model. A daily water balance model was used to quantify the actual and future peak water demand of the district. The reliability of each hydrant under baseline and future demand was calculated using a stochastic hydraulic model and the failure zones identified. Under the current design, the system can tolerate a peak demand discharge up to 1,500 l.s (-1), which is below the 2050s' average (1,720 l.s(-1)). Above that value, the performance of the system will fall drastically as the number of unreliable hydrants will increase. In the future, assuming the same cropping pattern, the threshold discharge (1,500 l.s(-1)) will be exceeded 80% of the time and, as an average, 20% of the system's hydrants will be failing during the peak demand periods. The adaptation options available to farmers and system managers in response to the increasing demand are discussed

Water scarcity and water gaps [Part 3. Regions and resources]

International audienc

Fractures et rareté hydriques [Partie 3. Espaces et ressources]

International audienc

Water scarcity and water gaps [Part 3. Regions and resources]

International audienc

Fractures et rareté hydriques [Partie 3. Espaces et ressources]

International audienc

Temperature Variability in Apulia Region (Italy) and its Impact on the Reference Evapotranspiration: Seasonal Based Analysis of the Period 1950 to 2003

The minimum, maximum, mean temperatures and reference evapotranspiration were considered in this paper for the purpose of trend analysis. The study, which was based on 38 monitoring stations, was carried out at a sub-national scale throughout Apulia region (Italy). The methodology of the nonparametric Mann-Kendall test and the progressive trend analysis were used for the trend detection. The second half of the 20th century (1950-2003) was investigated on seasonal and annual scales. The results generally showed a warming process, which has taken place especially from the mid-1970s, and an acceleration of the atmospheric evaporative demand thereafter. The latter had a significant positive trend, while the period before the break point of the 70s had a cooling effect. Finally, the warming was more pronounced in the case of minimum temperature