Data di Pubblicazione:
2018
Citazione:
Water fluxes and balance in a toposequence of rice paddies in Northern Italy / S. Cesari de Maria, M. Rienzner, A. Mayer, E.A. Chiaradia, D. Masseroni, E. Casati, M. Romani, A. Facchi. - In: GEOPHYSICAL RESEARCH ABSTRACTS. - ISSN 1607-7962. - 20:(2018 Apr). ((Intervento presentato al convegno EGU General Assembly tenutosi a Vienna nel 2018.
Abstract:
Paddy soils are the most widespread example of hydromorphic soils having an economic value. They are present
in land devoted to rice growing, where submersion and waterlogging conditions occur during all or part of the
cropping season. Rice is cropped on about 160 million hectares worldwide, with a production close to 700 million
tons. European production is quantitatively modest (about 3 million tons of paddy rice) and concentrated in a few
areas including Italy, which is the largest European producer with over half of the total production grown on an
area of 220 thousand hectares, predominantly located on the left bank of the Po River (Northern Italy). This area is
characterized by many peculiarities: a historical abundance of surface water, an ancient and extensive network of
unlined irrigation and drainage channels, a complex geo-morphologic and hydro-geologic structure formed by wide
fluvioglacial conoids (Pleistocene) cut by river valley lowlands (Holocene), and the presence of one of the largest
aquifers in Europe. Phreatic water level varies in space and time and it rises up to the soil surface in some areas as a
consequence of the summer flooding of paddies. Soils are generally loam/sandy-loam developed on sandy alluvial
sediments, with coarser textures occurring along river valleys and finer granulometries in the older (paleo)soils in
the northernmost area. Thus, soils are generally moderately permeable, and only the peculiar agricultural practices
adopted in rice cultivation (mainly flooding) lead to the formation of a dense and low permeable layer below the
ploughed horizon, which strongly influences vertical percolation. Additionally, in paddy areas, local topography
activates lateral water exchanges in the unsaturated zone. In particular, in a toposequence of paddy fields, lower
paddies may receive seepage and runoff from paddies located upslope. This study (funded by Fondazione Cariplo,
grant n 2014-1260), investigates the hydrology and water use efficiency of a group of four paddies located in
Northern Italy and characterized by different elevations (A B > C > D) during two years (2015-2016). Water
fluxes and storages were quantified by coupling field monitoring and hydrological modelling. The main outcomes
are: i) the Darcy’s law, applied considering lab-measured soil hydraulic conductivities of the most impervious
horizons and field monitored data (soil profile description, ponding water and groundwater levels), is a valuable
tool for the estimation of vertical percolation in flooding conditions; ii) significant variations of vertical percolation
in time may be observed even for the same paddy due to fluctuations in groundwater table depth; iii) surface and
subsurface lateral water exchanges activated by the slope provide extra water supply to paddies at the bottom of
the toposequence; iv) none of the paddies in a toposequence is representative of the whole area; thus, the spatial
scale of monitoring must be enlarged when computing water balances of rice areas.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
S. Cesari de Maria, M. Rienzner, A. Mayer, E.A. Chiaradia, D. Masseroni, E. Casati, M. Romani, A. Facchi
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