Proceedings of the 39th IAHR World Congress最新文献

In the present work, a selection of drip irrigation emitters used in greenhouse horticultural crops in the province of Almeria, Spain, were hydraulically evaluated, studying their hydraulic behavior and whether they meet with quality standards. Since manufacturers are offering lower flow emitters less spaced, all drippers tested are low flow. The hydraulic characterization will indicate the discharge and emission uniformity of the manufactured emitters, which are the fundamental parameters for the study of water use efficiency in drip irrigation. In the province of Almeria, water is a limiting factor due to the existence of a semi-arid climate, and, in addition, these limited water resources are used by intensive agriculture which causes a high consumption of these resources.

In total, 21 emitters have been evaluated, including all possible drippers according to their type of insertion (inline, pinched or online and interlinea), hydraulic behaviour (non-compensating and self-compensating) and, within the compensating ones, (anti-draining and non anti-draining). Its flow rates are between 1 and 2.4 l/h, except for a non-compensating interlina emitter of 3.8 l/h.

To carry out these tests, the criteria of the ISO 9261:2004 standard have been followed, calculating the coefficient of manufacturing variation and the emitter discharge equation on a test bench located in the La Mojonera Centre (Almeria) of the IFAPA (Andalusian Institute of Agricultural and Fishing Research and Training).

The results of this study show very good behavior in most of the emitters, and, as a consequence, a low coefficient of manufacturing variation has been obtained. The discharge equation obtained in the laboratory shows a low emisión exponent in the self-compensating emitters, being, therefore, the compensation of the pressures very high in all cases. No statistically significant differences have been found between self-compensating and non-compensating emitters by analysing their manufacturing variation coefficients. Nor have any significant differences been found between self-compensating emitters according to whether they are anti-draining or non-anti-draining, considering also the coefficient of variation. In anti-draining emitters, all closing pressures are not satisfied according to the standard, and are exceeded with very high values. The opening pressure is met for two of the four emitters, and one of those that does not meet it does so with a very large value.

The catastrophic flood following the Gleno dam break, which occurred in 1923, has been investigated in the literature (Pilotti et al., 2011, Milanesi and Pilotti, 2021) considering the 20 km long steep alpine valley separating the dam location from the hamlet of Corna. In this contribution, we investigate the propagation of the flood wave from Corna, where the computed hydrograph from previous investigation provides the upstream boundary condition, as far as the Lake Iseo outlet in Sarnico, where two controversial documents attest its effect on the lakeshore. In the middle, the flood crossed 30 km of a wide pre-alpine floodplain that has been deeply modified over the last century  and crossed 25 km of a deep lake.

The simulation has been accomplished by coupling 2 different 2D solver of the Shallow Water Equations: the well-known HEC-RAS 2D software was used to cover the floodplain from Corna up to the Lake Iseo inlet, while a finite volume scheme was used to simulate the lake behaviour in response to the incoming flood. The finite volume scheme used to model the lake is based on the WAF solver developed by Toro (Toro, 2001) and further adapted to account for the geometry of lake Iseo using an unstructured mesh. The scheme used retains shock-capturing capabilities and well-balanced properties able to withstand the constantly changing bathymetry of the lake as well as the unsteadiness of the hydrodynamics modelled. As a first step, the simulation was performed on the topography derived from the LIDAR DTM surveyed in 2008-2009. A computational mesh was built with average grid size of 10 m aligned in correspondence of levees and other singularities. This first simulation dramatically shows how the propagation of the flood wave was affected by the presence of linear structures such as levees and road embankments, absent in 1923 as shown by historical maps. For this purpose, the linear structure that affect the flow was removed from the 2008-2009 DTM and a second simulation was performed in order to compare the different flow hydrograph at the inlet of the lake.

An important fallout of the modeling effort is the reconstruction of the 1923 original bathymetry of the river in Valle Camonica, to be compared with the present one, affected by 100 years of river training works. The comparison of the flood propagation using the two bathymetries highlights the consequences of systematic hydraulic works on the hazard distribution for the same event. Paradoxically, the residual risk is now much higher than 100 years ago. Moreover, the simulations show that the claim of a 50 cm high bore at the inlet of the Oglio river is unsubstantiated by the model results and that an important request of damages was probably based on a false statement.

Since 1970 the number of freshwater species has suffered a decline of 83% worldwide and anthropic activities are considered to be major drivers of ecosystems degradation. Linking the ecological response to the multiple anthropogenic stressors acting in the system is essential to effectively design policy measures to restore riverine ecosystems. However, obtaining quantitative links between stressors and ecological status is still challenging, given the non-linearity of the ecosystem response and the need to consider multiple factors at play. This study applies machine learning techniques to explore the relationships between anthropogenic pressures and the composition of fish communities in the river basins of Castilla-La Mancha, a region covering nearly 79 500 km² in central Spain. During the past two decades, this region has experienced an alarming decline of the conservation status of native fish species. The starting point for the analysis is a 10x10 km grid that defines for each cell the presence or absence of several fish species before and after 2001. This database was used to characterize the evolution of several metrics of fish species richness over time, accounting for the species origin (native or alien), species features (e.g. pollution tolerance) and habitat preferences. Random Forest and Gradient Boosted Regression Trees algorithms were used to relate the resulting metrics to the stressor variables describing the anthropogenic pressures acting in the rivers, such as urban wastewater discharges, land use cover, hydro-morphological degradation and the alteration of the river flow regime. The study provides new, quantitative insights into pressures-ecosystem relationships in rivers and reveals the main factors that lead to the decline of fish richness in Castilla-La Mancha, which could help inform environmental policy initiatives.