poster - International Conference of Agricultural Engineering

This method consists of covering the AWR surface with a shade cover that is supported by a
double reticulated frame structure made of steel or polyamide cables (Martínez-Alvarez et
al., 2009). The cables are anchored either into the storage wall or to galvanised steel posts
bolted to concrete footings. A black double polyethylene fabric, which is porous to water, but
reduces light transmission and wind effect on the water by 99% and 92% respectively
(Gallego-Elvira et al., 2011), is then attached between the frames and suspended over the
AWR.
Concerning the previous research, SSCCs have demonstrated to be an efficient water quality
improving technique for AWRs without inlets or outlets of water (i.e. without flow regulation
function; Maestre-Valero et al., 2011). However, they have not been evaluated so far for
AWRs frequently used for irrigation subjected to ongoing water renewals, where the
regulation of the reservoir is likely to smooth the effects of shading on water quality.
Besides, as a result of increasing water shortages that mainly affect irrigated agriculture, the
use of no-conventional water resources such as reclaimed water currently depicts an
alternative option that complements the conventional water supply in intensive agricultural
systems. However, irrigation with reclaimed water needs to settle some conditions that
minimize the risk of contamination (pathogens or toxic substances) of agricultural products,
soil and groundwater (Angelakis et al., 2003). Thus, both physical and chemical and
microbiological water quality parameters need to be set up and evaluated.
This study aimed at analyzing the changes in physical (water temperature, T w ; electrical
conductivity, EC; chlorophyll-a, Chl-a; dissolved oxygen, DO; and turbidity, W t ), chemical
(cations: B + , Ca + , K + , Mg + , Na + and S + and anions: Cl - , NO 3 - and SO 4 2- ) and microbiological
(E-coli and fecal coliforms) parameters of water quality in uncovered and covered AWRs
used for irrigation.
2. Materials and Methods
2.1. AWRs characteristics
Four AWRs that regulated flows for irrigation, located in the Segura River Basin, southeastern
Spain, were monitored for a year (March-2011 to March-2012). Two of the AWRs
were uncovered (named U 1 and U 2 ) whereas the two other were covered (named C 1 and C 2 )
with a SSCC made of double black polyethylene fabric. All AWRs, with similar geometric
characteristics, were supplied with the same water sources: a large reservoir that feeds the
entire irrigation area with surface water through a canal, in which is incorporated to a lesser
extent reclaimed water from a water treatment plant wastewater.
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2.2. Data collection and analyses
During the one-year experimental period, physical, chemical and microbiological analyses
were performed. Physical parameters were monthly determined using a multi-parametric
instrument (OTT-DS5) placed in the middle of the reservoir to measure in situ T w , EC, Chl-a,
DO and W t . Profiles were taken from the bottom to the surface and readings at depths of 0.2,
0.5, 1.5, 2.5, 3.5 and 4.5 m were selected from such profile measurements. Additionally,
chemical (cations: B + , Ca + , K + , Mg + , Na + and S 2+ and anions: Cl - -
, NO 3 and SO 2- 4 ) and
microbiological analyses (fecal coliforms and E-coli) were performed by taking water samples
at 1 m depth and analyzing them in laboratory according to Spanish legal framework for
water quality monitoring and sampling (UNE-EN 25667-1,2 and 3).
Water quality data were interpreted using an analysis of variance and the Tukey’s range test,
at a 95% confidence level was also applied (statistical software package Statgraphics Plus
v.5.1). Statistical analysis results indicated that throughout the trial period, Chl-a, EC and DO
did not vary significantly with depth in both covered and uncovered AWRs and hence those
data were graphed as the average of all of the monitored depths.
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