1,721,011 research outputs found
Il Bilancio Idrologico nei Bacini a Forte Contributo Nivale : Il caso del Torrente Mallaro
No full textClimate Change Effects upon Pasture in the Alps: The Case of Valtellina Valley, Italy
No full textIn this study, we assessed the potential effects of climate change upon the productivity of mountain pastures in the Valtellina valley of Italy. Two species, Trisetum flavescens and Nardus stricta, among the most abundant in Italian pastures, were chosen for the simulation of low- and high-altitude pastures, respectively. We introduced some agroclimatic indices, related to growing season parameters, climate, and water availability, to evaluate the impacts of climate change upon pasture production. First, the dynamic of the pasture species was evaluated for the present period using the climate-driven, hydrologically based model Poli-Hydro, nesting the Poli-Pasture module simulating plants growth. Poli-Pasture was validated against yield data, at province scale, and at local scale. Then, agroclimatic indices were calculated. Subsequently, IPCC scenarios of the Fifth and Sixth Assessment Reports (AR5 and AR6) were used to project species production and agroclimatic indices until the end of the 21st century. In response to increased temperature under all scenarios, a large potential for an increased growing season length and species yield overall (between +30% and +180% for AR5 at 2100) was found. Potential for decreased yield (until −31% for AR5) is seen below 1100 m asl in response to heat stress; however, it is compensated by a large increase higher up (between +50% and +140% for AR5 above 2000 m asl). Larger evapotranspiration is foreseen and larger water demand expected. However, specific (for hectares of pasture) water use would decrease visibly, and no significant water limitations would be seen. Results provide preliminary evidence of potential livestock, and thereby economic development in the valley at higher altitudes than now
Ex-post assessment of climate and hydrological projections: reliability of CMPI6 outputs in Northern Italy
No full textThis paper presents a validation of outputs from some GCMs of the CMIP6 project when used to assess climate projection and hydrological flows at a catchment scale for the case study area of the Lombardy region (Northern Italy). The modeling chain consists of (i) a choice of climatic scenarios from 10 GCMs of the CMIP6, (ii) the application of a stochastic downscaling procedure to make projections usable at the local scale, and (iii) the use of a semi-distributed physically based hydrological model Poli-Hydro for the generation of hydrological scenarios. Data on observed precipitation and temperature were collected from automatic weather stations, and the hydrological budget of four target catchments within the study area was assessed using Poli-Hydro. An ex-post (back-casting) analysis was performed upon the control data series from the GCMs by comparing statistics of relevant climate variables and model-simulated discharges against observed counterparts during the historical period 2002-2014. Then, during 2015-2021, the goodness of projections was assessed using confidence intervals. Our results show that the accuracy of GCMs in representing regional climate is not always reflected in a credible evaluation of local hydrology. The validation of climate patterns provides somewhat poor results; thus, the interaction among climate and hydrology needs to be explored carefully to warrant the credibility of hydrological scenarios. Overall, the spatial and temporal consistency of GCM projections, as explored here climatically and hydrologically, provides a clue about their dependability for basin scale management
A novel comparative statistical and experimental modeling of pressure field in free jumps along the apron of usbr type i and ii dissipation basins
Full text linkDissipation basins are usually constructed downstream of spillways to dissipate energy, causing large pressure fluctuations underneath hydraulic jumps. Little systematic experimental investigation seems available for the pressure parameters on the bed of the US Department of the Interior, Bureau of Reclamation (USBR) Type II dissipation basins in the literature. We present the results of laboratory-scale experiments, focusing on the statistical modeling of the pressure field at the centerline of the apron along the USBR Type I and II basins. The accuracy of the pressure transducers was ±0.5%. The presence of accessories within basinII reduced the maximum pressure fluctuations by about 45% compared to basinI. Accordingly, in some points, the bottom of basinII did not collide directly with the jet due to the hydraulic jump. As a result, the values of pressure and pressure fluctuations decreased mainly therein. New original best-fit relationships were proposed for the mean pressure, the statistical coefficient of the probability distribution, and the standard deviation of pressure fluctuations to estimate the pressures with different probabilities of occurrence in basinI and basinII. The results could be useful for a more accurate, safe design of the slab thickness, and reduce the operation and maintenance costs of dissipation basins
Field study of mass balance, and hydrology of the West Khangri Nup glacier (Khumbu, Everest)
No full textThe depiction of glaciers' dynamics in the high altitudes of Himalaya and the hydrological fluxes therein is often limited. Although sparse seasonal (snow/ice) melt data may be available, dense precipitation networks are not available everywhere, and especially in the highest area, and the assessment of accumulation processes and mass balance may be difficult. Hydrological fluxes are little measured in the high altitudes, and few studies are available covering flow modeling and flow partitioning. Here, we investigate the snow accumulation, ice melt, and mass balance ofWest Khangri Nup (WKN) glacier (0.23 km2, mean altitude 5494 m asl), which is a part of the Khumbu glacier in the Everest region, where information of precipitation and hydro-glaciological dynamics in the highest altitudes was made available recently in fulfillment of several research projects. Weather, glaciological, snow pits, hydrologic, and isotopic data gathered during field campaigns (2010-2014) on the glacier and at the EVK2CNR Pyramid site were used to (i) set up the Poli-Hydro glacio-hydrological model to describe ice and snow melt and hydrological flows from the glacier, and (ii) investigate seasonal snow dynamics on this high region of the glacier. Coupling ice ablation data and Poli-Hydro simulation for ca. 5 years (January 2010-June 2014), we estimate that the WKN depleted ca.-10.46 m of ice water equivalent per year m IWE year-1 (i.e., annually ca.-2.32 meter of water equivalent per year m WE year-1). Then, using snowpack density and isotopic (δ18O) profiles on the WKN, we demonstrate that the local snowpack is recent (Fall-Winter 2013-2014) and that significant snow accumulation did not occur recently, so this area has not been a significant one of accumulation recently. Analysis of recent snow cover from LANDSAT images also confirms snow dynamics as depicted. Our study presents original data and results, and it complements present studies covering glaciers' mass balance as well as an investigation of accumulation zones in the Everest region and the Himalayas, which is also potentially helpful in the assessment of future dynamics under ongoing climate change
Assessing the impact of climate change upon hydrology and agriculture in the Indrawati Basin, Nepal.
No full textAgriculture is sensitive to climate change, especially to temperature and precipitation changes. The purpose of this study was to evaluate the climate change impacts upon rain-fed crops production in the Indrawati river basin, Nepal. The Soil and Water Assessment Tool SWAT model was used to model hydrology and cropping systems in the catchment, and to predict the influence of different climate change scenarios therein. Daily weather data collected from about 13 weather stations during 4 decades were used to constrain the SWAT model, and data from two hydrometric stations used to calibrate/validate it. Then management practices (crop calendar) were applied to specific Hydrological Response Units (HRUs) for the main crops of the region, rice, corn and wheat. Manual calibration of crop production was also carried, against values of crop yield in the area from literature. The calibrated and validated model was further applied to assess the impact of three future climate change scenarios (RCPs) upon the crop productivity in the region. Three climate models (GCMs) were adopted, each with three RCPs (2.5, 4.5, 8.5). Hence, impacts of climate change were assessed considering three time windows, namely a baseline period (1995-2004), the middle of century (2045-2054) and the end of century (2085-2094). For each GCM and RCP future hydrology and yield was compared to baseline scenario. The results displayed slightly modified hydrological cycle, and somewhat small variation in crop production, variable with models and RCPs, and for crop type, the largest being for wheat
Impact of prospective climate change on water resources and crop yields in the Indrawati basin, Nepal
No full textThe study aimed at developing a tool to investigate the effect of prospective climate change (until 2100) on hydrology and productivity of rain-fed crops (wheat Triticum L., maize Zea Mais L., and rice Oryza L.) in the Indrawati river basin, Nepal, Himalaya. Climate scenarios from 3 climate models (GCMs), namely CCSM4, EC-Earth and ECHAM6, each one under 3 different representative concentration pathways (RCPs) were fed to Soil and Water Assessment Tool (SWAT) and hydrological fluxes and crop yields were estimated for two time windows, i.e. half century (2045-2054) and end of century (2085-2094) against control run decade (1995-2004). The results foresee considerable potential changes of hydrological fluxes (from -26% to +37% yearly, with large difference seasonally and between models and RCPs), and potential changes of crop production (-36% to +18% for wheat, -17% to +4% for maize, and -17% to +12% for rice, again with differences between models and RCPs), also in term of yearly variability, potentially affecting food security. The CCSM4T model projected larger changes in hydrology and reduction in crop yields than other models. Wheat was found to be more vulnerable than maize and rice to climate change
Modelling the effects of potential climate change on the dynamics of multi-species mountain pastures: A case study in Gran Paradiso National Park, Italy
No full textCONTEXT
Pasture dynamics of Alpine areas are linked to the complex cryospheric hydrology of Alpine catchment and to the interspecies competition, which are in turn expected to change remarkably under prospective global warming scenarios.
OBJECTIVE
This study aimed at assessing the impact of climate change on the productivity of mountain pastures in the Gran Paradiso National Park (Italy).
METHODS
The hydrological model Poli-Hydro was used, coupled with the Poli-Pasture model, able to simulate pasture growth, which was further integrated with CoSMo model to consider interspecific competition. Two (competing) species were chosen for low altitude LowAlt areas (below 1800 m asl), Trifolium alpinum and Dactylis glomerata, and two for high altitude HighAlt areas (above 1800 m asl), Festuca rubra and Nardus stricta. Model tuning and evaluation were performed against estimates of leaf area index (LAI), derived from satellite imagery during 2005–2019. Then, climate change impacts were projected until 2100 by considering four IPCC AR6 scenarios and six GCMs. Target variables included a set of agroclimatic indices, LAI and pasture yield.
RESULTS AND CONCLUSIONS
Due to the projected increase in temperatures during the XXI century, a measurable potential increase in productivity would be expected, especially in the highest areas (up to +97% by 2050, and + 123% by 2100 for the SSP5–8.5 scenario). The relative abundance of pasture species appears to remain mostly stable; at most, the species with higher fodder value even increases slightly. This suggests that a loss in the overall quality of biomass should not occur. These results provide preliminary evidence for the potential development of livestock farming, and thus of a relevant part of the economy in the valleys, at higher altitudes than now. However, to a certain extent pasture performance could be threatened by the projected reduction in summer rainfall, and possibly spreading of pests with increasing temperature.
SIGNIFICANCE
The results obtained here could be useful for policy makers, and scientists in the field of pasture/grasslands management, to depict scenarios of future productivity, and to support redefinition of periods, and areas designated for grazing activities in the mountains
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