1,721,034 research outputs found
Green roof benefits for reducing flood risk at the catchment scale
No full textAmong the European countries, Italy is one of
the most susceptible to hydrogeological instability events
related to the risk of flooding in intensely populated basins,
especially inside the Po Valley. A clear example is the
Seveso river basin, whose territories are regularly stressed
several times per year by flooding events, which in recent
years have increased in frequency and intensity. However,
it is now impossible to intervene with structural projects
aimed at the lamination of flood events, even in modest
return periods because of excessive urbanization and continuous
residential and industrial expansion. Using extensive
and detailed green roof parameters, this study
modelled the hydrologic effect of three hypothetical roof
greening scenarios at the catchment scale (conversion of 5,
30, and 100 % impervious to green roofs). The modelling
of the green roof performances was performed using the
Environmental Protection Agency (EPA) Storm Water
Management Model (SWMM) and was calibrated over five
years of hourly discharge measurements at the closure
section of the basin. Hydrologic modelling demonstrated
that widespread green roof implementation significantly
reduces peak runoff rates and runoff volumes by up to 30
and 35 %, respectively, in the case of 100 % conversion
Water saving at the field scale with Irrig-OH, an open-hardware environment device for soil water potential monitoring and irrigation management
No full textEffect of the representative source area for eddy covariance measurements on energy balance closure for maize fields in the Po Valley
No full textModelling water requirements of greenhouse spinach for irrigation management purposes
No full textEstimating water requirements of plants cultivated in greenhouse environments is crucial, both for the design of greenhouse irrigation systems and the improvement of irrigation scheduling. Spinach is one of the main vegetables sold as ‘ready-to-eat’ bagged produce; it is very sensitive to water stress and thus requires accurate irrigation. In this work, a water balance model simulating the daily irrigation need for greenhouse crops based on the FAO-56 ‘single crop coefficient’ method was designed and applied (FAO-56-GH). Two experiments were conducted on two spinach varieties grown in pots in different periods. For each experiment, four nitrogen treatments were considered. Irrigation was managed weighing the pots every day, and restoring soil water to field capacity. Crop coefficient (Kc) values were calibrated using data of the first experiment, the model was successively validated using the second dataset. Results showed a good model performance both in the validation and calibration periods (R2 = 0.80 and 0.84, RMSE = 0.41 and 0.21 mm day−1, NSE = 0.78 and 0.83). ANOVA test revealed a scarce dependence of irrigation needs to nitrogen treatments. This study suggests the possibility of adopting the FAO-56-GH model with site-specific Kc to improve irrigation management and planning in greenhouse environments
Is the soil water potential a reliable variable for irrigation scheduling in case of peach orchards?
No full textCrop water status monitoring in the case of high-value crops such as fruit trees is generally carried out through periodic measurements of physiological indicators on leaves or fruits operated by sophisticated instruments and complex procedures. These measurements are very often difficult to translate in an irrigation advice. Soil water potential (SWP), on the contrary, is a basic soil water status variable correlated with plant water uptake, which can be easily measured by sensors. It can provide a useful support for irrigation scheduling at the field scale, enhancing the water saving in agricultural areas.
In this work we present the results of an experimental activity carried out in the agricultural season 2014 on a peach orchard located at Lodi (Northern Italy), with the purpose of evaluating the effects of an irrigation scheduling based on continuous SWP measurements collected at two soil depth (-15 and -35 cm) on the crop water status and the peach production, with respect to the farmer’s commonly adopted irrigation practice. In order to answer the question in the title, periodic measurements of physiological parameters such us leaf water potential (LWP), stomatal resistance (rs), transpiration (E) and crop water stress index (CWSI) were performed, in association with the monitoring of fruit size evolution and fruit sugar content at the harvest. Al these variables were detected to assess the crop physiological state of the trees subjected to the two different irrigation treatments, with the final scope to show if the irrigation scheduling based on SWP measurements compromised the quality and quantity of the peach production. The results showed that, even for the irrigation treatment based on SWP measurements, no considerable crop water stress occurred. In particular, the most extreme values of LWP, rs, E, and CWSI measured at midday were respectively -2 MPa, 45 s m-1, 1.4 mm h-1 and 0.5, in good agreement with those observed by many researches for well-watered orchards in Mediterranean areas.
In conclusion, we can stress that SWP monitoring can be considered a reliable alternative to the more costly and time consuming physiological measurements for the irrigation scheduling of fruit crops such as peach orchards, providing continuous information about the soil water status, preventing the plant water stress and reducing the irrigation water consumption at the farm scale
Self-made microlysimeters to measure soil evaporation : a test on aerobic rice in northern Italy
No full textSoil water balance researches aimed at improving crop water use efficiency often require the determination of soil evaporation. In this technical note, the performance of simple and cheap self-made microlysimeters for the measurement of soil evaporation was tested in an aerobic rice field managed by intermittent irrigation. Six microlysimeters obtained by cutting commercial PVC pipes and closing the bottom ends with caps were positioned in appropriate PVC outer casings installed into the soil. Three measurement campaigns (for a total of 11 measurement periods) were carried out in different vegetation cover conditions (rice development, rice maturity and after the crop harvest). Evaporation amounts were analysed with respect to climatic data, vegetation cover and soil water status and, finally, compared with the simulated results of a FAO Penman–Monteith “dual crop coefficient” model implemented with site-specific data. Evaporation rates in the three campaigns were closely dependent on the evaporative demand of the atmosphere ETo (R2 = 0.96, 0.98, 0.96), while the slope of the linear regression curve was strongly related to the vegetation cover (b = 0.29, 0.12, 0.94); soil water content, always rather high during the experiments, did not affect the evaporation rate. Measured and simulated evaporation amounts showed a close agreement: the linear regression was characterized by slope and R2 of 0.98 and 0.95, while RMSE and NSE indices were 0.15 and 0.94. From the tests conducted, we can conclude that the self-made microlysimeters presented in this note are affordable instruments for measuring soil evaporation, at least in temperate climate conditions
Estimation of zero-plane displacement height and aerodynamic roughness length on rice fields
No full textStime accurate della lunghezza aerodinamica (z0) e dell’altezza di dislocamento (d) sono estremamente importanti per molti modelli che simulano gli scambi di massa ed energia nei sistemi suolo-vegetazione-atmosfera a differenti scale spaziali. In passato sono stati fatti molti sforzi per misurare direttamente z0 e d attraverso rilevamenti multilivello della velocità del vento su superfici vegetate in modo omogeneo: i risultati presenti in letteratura sono tuttavia ancora scarsi per molte tipologie di vegetazione e di conseguenza spesso si ricorre a regole pratiche che forniscono una stima approssimata dei valori di z0 e d. In questo studio, i valori di z0 e d per l’intera stagione agraria si sono ottenuti da misure di turbolenza effettuate ad un solo livello tramite una stazione micrometeorologica eddy covariance installata sull’argine di separazione tra due appezzamenti coltivati a riso nel Nord Italia, caratterizzati da differenti gestioni irrigue (sommersione continua e irrigazione intermittente con riso aerobico). I risultati mostrano che durante l’intera stagione agraria, z0 e d sembrano essere ben correlati (R2 maggiore del 90%) con l’altezza della vegetazione (hv): il valore medio del rapporto tra d e hv è pari a circa 0.75 per entrambi i trattamenti irrigui, mentre il rapporto tra z0 e hv è di circa 0.06 per il riso caratterizzato da sommersione e 0.05 per il riso aerobico. Infine, nessuna chiara correlazione si è riscontrata tra le condizioni di stabilità atmosferica o la velocità del vento ed i valori di z0 e d. Parole chiave: lunghezza aerodinamica, altezza di dislocamento, tecnica eddy covariance, riso in sommersione continua, riso aerobico, Nord Italia.The estimation of aerodynamic roughness length (z0) and zero-plane displacement height (d) is of primary importance in the application of a number of models that simulate soil-vegetation-atmosphere interactions at different spatial scales. Many efforts to directly measure z0 and d in the case of various surfaces were conducted in the past from multi-level measurements of wind speed over homogeneous surfaces, but results reported in the literature are still rare for some canopies and can only be used as a rule of thumb. In this work, values of d and z0 along the whole agricultural season for two rice fields located in northern Italy and characterized by different irrigation managements (continuous flooding and intermittent irrigation) were obtained from single level turbulence measurements performed by an eddy covariance (EC) system installed on the levee between the two fields. Throughout the growing season, d and z0 appeared to be well correlated (R2 greater than 90%) with the vegetation height (hv) and the mean value of the ratio between d and hv was about 0.75 for both rice fields, while the ratio between z0 and hv was about 0.06 and 0.05 respectively for the flooded and the intermittent irrigation treatments. Moreover, d and z0 did not show any clear dependence on wind speed or stability conditions of the atmosphere. Keywords: aerodynamic roughness length, zero-plane displacement height, eddy covariance, paddy field, aerobic rice, northern Italy
Integrating flux measurements of a single eddy-covariance system and Penman-Monteith modeling to estimate rice evapotranspiration under multiple irrigation regimes
No full textItaly is the leading rice producer in Europe, with over half of total production, almost totally concentrated in a large traditional paddy rice area between the Lombardy and Piedmont regions, in the north-western part of the country, where irrigation is predominantly carried out by continuous flooding. The high water requirements have encouraged the introduction of water saving irrigation practices, as delayed flood irrigation after sowing in dry soil and intermittent irrigation (aerobic rice). In the agricultural season 2013 an intense monitoring activity was conducted on three experimental fields located in the area, characterized by different irrigation regimes (traditional flood irrigation, flood irrigation after sowing in dry soil, intermittent irrigation), with the aim of comparing the water balance components. Actual evapotranspiration (ET) is one of the components which is more pretending in terms of monitoring effort and cost.
This work explores the possibility of using a single eddy covariance system in combination with Penman-Monteith (PM) type models for the determination of ET fluxes for the three irrigation regimes. An eddy covariance station was installed on the levee between the traditional flooded and the aerobic rice fields at the experimental site, to contemporaneously monitor the ET fluxes from these two treatments as a function of the wind direction. A detailed footprint analysis was conducted (three different analytical models were applied) to determine the position and the size of the footprint area at each monitoring time step (30-min). Two sets of half-hourly ET values, one for each irrigation regime, were therefore obtained, each one comprising about 10% of the daytime time steps over the whole agricultural season. To confirm the reliability of the measured ET fluxes, the energy balance closure was computed for the two fields and it resulted in an imbalance lower than 10% for both the irrigation treatments.
The two eddy covariance data-sets, together with other observational data (i.e., soil and water evaporation measured by micro-lysimeters) were then used to calibrate three Penman–Monteith type models for the estimation of the rice crop transpiration (T), the soil evaporation (ES), and the evaporation from the water covering the soil in the case of flooded regimes (EH20), respectively. The models were implemented using the available agro-meteorological data detected over the rice canopies and the periodically measured values of crop parameters (leaf area index, crop height), obtaining satisfactory calibration results. Then, the calibrated models were used to compute the complete hourly ET data series for the three irrigation regimes
Evaluating longitudinal dispersion of scalars in rural channels of agro‐urban environments
Full text linkIn agro-urban environments, the water resource conveyed by rural channels is susceptible to a gradual impoverishment due to the continuous combined sewer overfow release, constituting a pending and urgent issue for water management companies and the entire community. Reliable one-dimensional longitudinal dispersion coefcients D are required to model and study the hydrodynamics and water quality patterns at the scale of rural channel networks. Empirical formulas are usually adopted to estimate D but the accuracy in the prediction could be questionable. In order to identify which are the most suitable formulas to determine D in rural channels, feld tracer measurements were carried out in three rural channels with typical geometry and confguration. The obtained D values were then compared with the most commonly used predicting formulas that the literature provides. The accuracy of the predictors was further checked by simulating diferent fow rates inside the tested channels by using a one-dimensional hydraulic model. Starting from the obtained results, indications and guidelines to choose the most suitable formulas to predict D in rural channels were provided. These indications should be followed when developing realistic quality models in the agro-urban environments, especially in those cases where direct measurements of the longitudinal dispersion coefcient D are not available
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