22 research outputs found
Multicriteria analysis for irrigation sustainable development: design and selection of irrigation systems
Doutoramento em Engenharia dos Biossistemas - Instituto Superior de AgronomiaThis study aimed to select the most sustainable irrigation methods able to obtain high water productivity considering economic aspects and water saving criteria for wheat and cotton in NE Syria. The models used are PROASPER for sprinkler, SADREG for surface and MIRRIG for drip irrigation. Multicriteria analysis (MCA) was used to rank a set of design alternatives considering water saving and economic priorities. For wheat, surface and sprinkler systems were applied. For cotton surface, sprinkler and drip methods were compared. All combinations were analysed for full and deficit irrigation.
Results for cotton show that drip irrigation is better than graded furrows for water saving but not a good option for economic priority unless the yield price increases. Sprinkler systems for cotton are rarely advantageous. For wheat, sprinkler systems are better than borders from water savings perspectives, showing an increased water productivity, as well as in economic terms leading to higher farmer’s income. MCA proved to be a very useful tool in a water scarce region to select the most appropriate irrigation systems considering the users preferences
Setting Irrigation Thresholds for Building a Platform Aimed at the Improved Management of Citrus Orchards in Coastal Syria.
Citrus is one of the most valuable crops in Syria, with the largest production areas being in
the coastal provinces of Tartus and Latakia, where this study was performed. A companion paper
reported on the basal crop coefficients derived from the field water balance and on the performance
assessment of various irrigation methods used in a citrus orchard located in the same region. That
study evidenced the need for the improved management of irrigation water, mainly reducing water
applications and increasing productivity, thus leading to the current research. The main objectives
consisted of (i) providing a set of reliable basal (Kcb) and average (Kc) crop coefficients to be used
in practice in the citrus orchards of the Syrian coastal area, while accounting for the diversity of
characteristics observed; (ii) to estimate the seasonal consumptive use of typical orchards under
different climate-demand and deficit-irrigation scenarios; and (iii) to assess possible water savings
and related yield reductions. The previously calibrated water balance model SIMDualKc was used
for these purposes. The computed Kcb values for the mid-season and average demand for water
ranged from 0.52, when the plant density was low, to 0.84, when plant density was very high. The
corresponding Kc values, which further reflected the impact of drip irrigation on controlling soil
evaporation, were 0.72 and 0.97, respectively. Overall, the consumptive use of water was estimated to
range from 867 to 1573 mm. The assessed water-saving scenarios consisted of adopting increased
management-allowed depletion (MAD) thresholds relative to the p depletion fraction for no stress:
MAD = 1.05, 1.10, 1.20, and 1.30 p. For trees under a very high climatic demand, water savings ranged
from 12 to 34%, but the yield losses induced by the water deficits ranged from 8 to 48%. Although
the selection of optimal strategies should be based upon economic terms, these may only be used
when the Syrian economy recovers from civil war and the current crisis. The present results show the
feasibility of adopting such MAD thresholds for building an irrigation management platform. The
data provided by the current study are valuable because they can be efficiently used to support of the
irrigation management of Syrian citrus production systems.info:eu-repo/semantics/publishedVersio
Drip vs. surface irrigation: a comparison focussing on water saving and economic returns using multicriteria analysis applied to cotton
Research PaperThis study explores the use of drip and surface irrigation decision support systems to select
among furrow, border and drip irrigation systems for cotton, considering water saving and
economic priorities. Data refers to farm field observations in Northeast of Syria. Simulation
of drip irrigation was performed with MIRRIG model for various alternatives: double and
single row per lateral, emitter spacing of 0.5 and 0.7 m, six alternative pipe layouts and five
self-compensating and non-compensating emitters. Furrow and border irrigation alternatives
were designed and ranked with the SADREG model, considering lasered and nonlasered
land levelling, field lengths of 50e200 m and various inflow discharges. A multicriteria
analysis approach was used to analyse and compare the alternatives based upon
economic and water saving criteria. Results for surface irrigation indicate a slight advantage
for long non-lasered graded furrows; non-lasered alternatives were selected due to economic
considerations. For drip irrigation, the best ranking is for systems having lower costs,
mainly with double rows per lateral and larger emitter spacing. Comparing surface and drip
irrigation systems, despite low cost, drip alternatives may lead to 28e35% water saving
relative to improved graded furrows, and increase water productivity from 0.43 kg m 3 to
0.61 kg m 3, surface irrigation provides higher farm returns. Drip irrigation is selected only
when high priority is assigned to water saving. Deficit irrigation does not change this pattern
of results. Apparently, adopting drip irrigation requires appropriate economic incentives to
farmers, changes in the structure of production costs and increased value of productioninfo:eu-repo/semantics/publishedVersio
Searching for Sustainable-Irrigation Issues of Clementine Orchards in the Syrian Akkar Plain: Effects of Irrigation Method and Canopy Size on Crop Coefficients, Transpiration, and Water Use with SIMDualKc Model
Citrus is one of the most valuable crops in Syria, with the largest production areas in the
Tartus and Latakia provinces. Water-saving policies have been adopted to modernize the irrigation
systems and increase water productivity. Following dedicated research, this study aimed to evaluate
the water balance in clementine trees irrigated with diverse methods and schedules using the
SIMDualKc software model. Two experiments are reported: one with 10–14 years old trees irrigated
with different methods (20072011) and the other with the same trees but now 1820 years old,
irrigated with different schedules (20152019). The SIMDualKc model successfully simulated the
soil water contents measured in the various field plots, with root mean square error values lower
than 0.004 m3 m3 and modeling efficiencies up to 0.83. The model-calibrated standard basal crop
coefficients (Kcb) were approximately constant throughout all growing stages, assuming values of
0.540.55 for the mature trees having smaller height (h) and fraction of ground cover (fc), and 0.64 for
older trees with larger canopies, i.e., larger h and fc. With drip irrigation, single Kc had a higher value
(1.14) at the end, non-growing, and initial stages, and a lower value (0.75–0.76) during mid-season
(Kc mid), because precipitation was lesser then, contributing less to soil evaporation. On the other
hand, Kc values were nearly constant with micro-sprinkler and surface irrigation techniques because
the ground was fully wetted. The Kcb values derived from the fraction of ground cover and height
(A&P approach) were similar to those obtained from the model, thus showing that the A&P approach
represents a practical alternative to estimate Kcb in the practice of irrigation management. The soil
water balance further revealed a large weight of the terms corresponding to the non-beneficial water
consumption and non-consumptive water use when the fraction wetted was large and the application
efficiencies were low. These terms were reduced, namely, evaporation losses when drip irrigation
was used. This study, thus, provides a valuable tool for improving the irrigation management, water
saving, and water productivity of Syrian citrus production systemsinfo:eu-repo/semantics/publishedVersio
Assessing the impact of LAI data assimilation on simulations of the soil water balance and maize development using MOHID-Land
Hydrological modeling at the catchment scale requires the upscaling of many input
parameters for better characterizing landscape heterogeneity, including soil, land use and climate
variability. In this sense, remote sensing is often considered as a practical solution. This study aimed
to access the impact of assimilation of leaf area index (LAI) data derived from Landsat 8 imagery on
MOHID-Land’s simulations of the soil water balance and maize state variables (LAI, canopy height,
aboveground dry biomass and yield). Data assimilation impacts on final model results were first
assessed by comparing distinct modeling approaches to measured data. Then, the uncertainty
related to assimilated LAI values was quantified on final model results using a Monte Carlo method.
While LAI assimilation improved MOHID-Land’s estimates of the soil water balance and simulations
of crop state variables during early stages, it was never sufficient to overcome the absence of a
local calibrated crop dataset. Final model estimates further showed great uncertainty for LAI
assimilated values during earlier crop stages, decreasing then with season reaching its end. Thus,
while model simulations can be improved using LAI data assimilation, additional data sources should
be considered for complementing crop parameterizationinfo:eu-repo/semantics/publishedVersio
Modeling soil water dynamics and pasture growth in the montado ecosystem using MOHID land
The southern Iberian Peninsula is characterized by evergreen oak woodlands (locally
known as montado), which constitute an important savanna-type agro-silvo-pastoral ecosystem.
This ecosystem is facing a progressive decline for several reasons, with the foremost being overgrazing.
Better management tools are necessary to accurately quantify the systems’ carrying capacity and
the sustainable stocking rates that prevent land degradation. The purpose of this study was to
determine whether the MOHID-Land model could adequately simulate soil water dynamics and
pasture growth in the montado ecosystem. The study area was located in the Alentejo region of
southern Portugal. The model successfully simulated soil water contents and aboveground biomass
during the 2010–2011 and 2011–2012 growing seasons, producing acceptable errors of the estimates
(0.015 RMSE 0.026 cm3 cm3; 279 RMSE 1286.5 kg ha1), and relatively high modeling
efficiencies (0.481 EF 0.882). The model was further used to simulate the same variables for
a longer period (1979/2009 seasons), to account for the effect of climate variability on model estimates.
Water balance and dry biomass estimates were found to be significantly different between rainfed
and irrigated pastures, as well as between the ten driest and ten wettest seasons, with the model
responding well to climate variability. The results showed the potential of using the MOHID-Land
model for improving pasture management in the montado ecosysteminfo:eu-repo/semantics/publishedVersio
Water use and soil water balance of Mediterranean tree crops assessed with the SIMDualKc model in orchards of southern Portugal
Orchards consist of complex agricultural systems, with a variety of characteristics (planting density, tree height,
training system, canopy cover, irrigation method, interrow management) influencing crop evapotranspiration
(ETc). Thus, irrigation water management requires finding crop coefficients (Kc) that represent the characteristics
of local orchards, evidencing the need for site specific data. The main objective of this study was to derive the Kc
of almond, olive, citrus, and pomegranate orchards in Alentejo, southern Portugal, wherein they became
dominant over the last decade. Monitoring was carried out in nine orchards, which management decisions were
performed by the farmers. The ETc was estimated from the soil water balance computed for each orchard using
the FAO56 dual-Kc approach with the SIMDualKc model. The model successfully simulated the soil water contents measured in the various fields along two growing seasons, with root mean square error values lower than
0.005 m3 m− 3 and modeling efficiencies from 0.363 to 0.782. The estimated basal crop coefficients (Kcb) for the
initial, mid- and end-seasons were respectively 0.22, 0.58, and 0.50 for almond; 0.32–0.33, 0.35–0.36, and
0.33–0.34 for olive; 0.40, 0.40–41, and 0.40–0.41 for citrus; and 0.24, 0.60, and 0.52 for pomegranate. Small
variations in olive and citrus Kcb values were found to be related to differences in the fraction of the ground
covered by trees’ canopies and tree height. The single Kc values, which included the component relative to soil
evaporation, were also estimated. Furthermore, evaluation of the soil water balance in the nine case studies
showed salinity effects in one almond orchard, mild irrigation water deficits in olive systems, and large nonconsumptive water use in citrus and pomegranate orchards. These results evidence the need for better management of orchards irrigation water in the region, and the current study provides for reliable information on the
Kc of tree crops to support improving the management of local orchard systems and the preservation of soil and
water resources. Aimed at these resources and the sustainability of their use, simulated alternative irrigation
schedules were performed, which identified possible water savings of 20 mm in case of olives, up to 855 mm for
citrus.info:eu-repo/semantics/publishedVersio
Water use, soil water balance and soil salinization risks of Mediterranean tree orchards in southern Portugal under current climate variability: Issues for salinity control and irrigation management
Secondary salinization has long been reported in the Roxo irrigation district (RID), southern Portugal, due to the
use of saline-prone irrigation water and the existence of poorly structured soils. This study assessed the soil water
and salt budgets in nine commercial orchards located in the RID using the multiple ion chemistry module
available in the HYDRUS-1D model during the 2019 and 2020 growing seasons. The studied crops were almond,
olive, citrus (orange, mandarin, and clementine), and pomegranate. The model successfully simulated soil water
contents measured in the different fields but there was a clear underestimation of the electrical conductivity of
the soil saturation paste extract (ECe) in some locations, while simulations of the sodium adsorption ratio (SAR)
were generally acceptable. Modeling errors were mostly associated with missing information on fertigation
events rather than related to the effects of irrigation water quality. The water and salt balances were also
computed for the 1979–2020 period. Considering the probability of non-exceedance of salt accumulation during
this period, the risk of salinity build-up was high to very high for the very dry years in most fields, except in the
citrus sites. The factors influencing the salt accumulation were the irrigation strategy, the seasonal irrigation and
rainfall depths, the duration of the crop growth period, the rainfall distribution in the late and non-growing
stages, the soil drainage conditions, and the irrigation water quality. For the current climate conditions and
irrigation water quality, the risk of soil salinity levels affecting crop development and yields was found to be
minor. This means that, despite salts tended to accumulate in the rootzone over a season, under current conditions the salinity stress did not reach harmful levels for plants. Only in two of the study sites, there was a need
to promote salt leaching. Hence, this study shows that soil salinization risks in the study area are low but, for
given locations during drier seasons, there is a need for tailored irrigation solutions aimed at the conservation of
soil and water resources.info:eu-repo/semantics/publishedVersio
Comparing sprinkler and surface irrigation for wheat using multi-criteria analysis: water saving vs. economic returns
Coping with water scarcity using supplemental irrigation of wheat (Triticum aestivum L.)
in the semi-arid northeast Syria is a great challenge for sustainable water use in agriculture.
Graded borders and set sprinkler systems were compared using multi-criteria analysis. Alternative
solutions for surface irrigation and for sprinkler systems were developed with the SADREG and
the PROASPER design models, respectively. For each alternative, two deficit irrigation strategies
were considered, which were characterized using indicators relative to irrigation water use, yields
and water productivity, including farm economic returns. Alternatives were ranked considering two
contrasting priorities: economic returns and water saving. A first step in ranking led to a selection of
graded borders with and without precise land levelling and of solid set and semi-permanent sprinkler
systems. Precise-levelled borders were better for water saving, while non-precise ones ranked higher
for economic returns. Semi-permanent set systems have been shown to be better in economic terms
and similar to solid set systems when water saving is prioritized. Semi-permanent sprinkler systems
rank first when comparing all type of systems together regardless of the considered deficit irrigation
strategy. Likely, border irrigation is appropriate when wheat is in rotation with cotton if the latter is
surface irrigated. When peace becomes effective, appropriate economic incentives and training for
farmers are required to implement innovative approachesinfo:eu-repo/semantics/publishedVersio
An integrated analysis of the eutrophication process in the Enxoé reservoir within the DPSIR framework
The Enxoé reservoir in southern Portugal has been exhibiting the highest trophic state
in the country since its early years of operation. The problem has attracted water managers’
and researchers’ attention as the reservoir is the water supply for two municipalities. Extensive
research was thus conducted over the last few years, including field monitoring and modelling
at the plot, catchment, and reservoir scales. This study now frames all partial findings within the
Driver-Pressure-State-Impact-Response (DPSIR) framework to better understand the eutrophication
process in the Enxoé reservoir. Agriculture and grazing were found to have a reduced role in the
eutrophication of the reservoir, with annual sediment and nutrient loads being comparably smaller or
similar to those reported for other Mediterranean catchments. Flash floods were the main mechanism
for transporting particle elements to the reservoir, being in some cases able to carry up three times the
average annual load. However, the main eutrophication mechanisms in the reservoir were P release
from deposited sediment under anoxic conditions and the process of internal recycling of organic
matter and nutrients. Reducing the P load from the catchment and deposited sediment could lead to
a mesotrophic state level in the reservoir. However, this level would only be sustainable by limiting
the P internal load ability to reach the photic zoneinfo:eu-repo/semantics/publishedVersio