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Advisor(s)
Abstract(s)
Water is a scarce resource in the Mediterranean
region where adverse climatic conditions promoting
water shortages tend to increase with climate
change. Under water scarcity conditions and high atmosphere
evaporative demand, the risks of decreased water
quality, and land salinization are major threats to the
sustainability of irrigated agriculture in this region. The
assessment of the quality of irrigation water is increasingly
important to ensure the maintenance of long-term
salt balance at a crop, farm, and regional scale. This
study is focused on the spatial and temporal variability of water quality for irrigation in the Alqueva reservoir
(Southern Portugal). The assessment was performed
every 2 months during a distinctive drought year
(2017) and included inorganic ions (Na+, Ca2+, Mg2+,
K+, NH4
+, Cl−, F−, SO4
2−, NO3
−, and NO2
−), pH, and
electric conductivity (ECW) of water. Sodium adsorption
ratio (SAR) was calculated, and potential soil permeability
problems were estimated. The assessment
showed significantly higher values of the physicochemical
parameters in the most upstream sites, located near
tributaries inflows, and an upward trend in ion concentrations
throughout the year, with significantly higher
concentrations of Na+, Mg2+, Cl−, and SO4
2, registered
through May to November, reflecting the severe drought
felt in the summer, autumn, and winter. The evaluation
of water quality for irrigation indicated a slight to moderate
risk of reduced infiltration rates, which should be
considered whenever sprinkler irrigation is used, mainly
in fine-textured soils, which are prevalent in the irrigated
area. The multivariate statistical approach, using principal
component analysis and factor analysis, identified
two principal components related to salinity and nutrient
concentrations. The cluster analysis revealed three
groups of similarity between samples pointing to a more
time- than space-controlled pattern. Overall, the temporal
dynamics of the water physicochemical parameters
could indicate that an abnormal annual distribution of
precipitation and temperature may distort seasonal differences.
To prevent water and soil degradation, a more
frequent assessment of the water quality should be considered,
allowing for the selection of appropriate soil
and water management measures in irrigated areas
Description
Keywords
irrigation areas water salinity SAR drought water quality assessment
Pedagogical Context
Citation
Tomaz A, Palma P, Fialho S, Lima A, Alvarenga P, Potes M, Salgado R. (2020). Spatial and temporal dynamics of irrigation water quality under drought conditions in a large reservoir in Southern Portugal. Environmental Monitoring and Assessment. 192(2), 93
Publisher
Springer Nature Switzerland AG