poster - International Conference of Agricultural Engineering

Physical, Chemical and Microbiological Effects of Suspended
Shade Cloth Covers on Stored Water for Irrigation
José F. Maestre 1* , Victoriano Martínez 1 , Belén Gallego 2 , Emilio Nicolás 3
1 Universidad Politécnica de Cartagena, ETSI Agronómica, Paseo Alfonso XIII, 48, 30203
Cartagena
2 Institut National de la Recherche Agronomique UMR 114 EMMAH INRA-UAPV Domaine
St Paul Site Agroparc 84914 Avignon cedex 9 FRANCE
3 Centro de Edafología y Biología Aplicada del Segura CEBAS-CSIC, Campus Universitario
de Espinardo, Espinardo, 20100 Murcia
*Corresponding author. E-mail: josef.maestre@upct.es
Abstract
The aim of this study was to identify the effect of installing suspended shade cloth covers
(SSCCs) on the water quality of agricultural water reservoirs (AWRs) for irrigation. Four
AWRs located in south eastern Spain were monitored for a year. Two of the AWRs were
covered with a black polyethylene SSCC, whereas the two others remained uncovered
during the experimentation period. Monthly, a multi-parametric instrument OTT-DS5 was
used and water samples were collected to determine and analyze the main physical,
chemical and microbiological water quality parameters respectively.
Results indicate a slight change in the thermal behaviour of the covered AWRs during the
warmer months. Electrical conductivity presented a slow and progressive dismissing caused
mainly by the frequent water renewals in the AWRs. The low transmitted solar radiation (1%
transmission through the cover) reduced dramatically the photosynthesis activity and the
algal bloom was highly limited. However, the oxygen levels were close to saturation
regardless the installation of the SSCC. The chemical parameters were not affected by the
installation of the cover and there was a significant reduction of E-coli and fecal coliforms in
covered AWRs. Overall, the results show that the implementation of SSCCs in AWRs
produces significant effects in the stored water quality, which are mainly beneficial for
irrigation purposes, especially with drip irrigation systems and reuse of treated waste water.
Keywords: Shade covers, water temperature, chlorophyll-a concentration, dissolved oxygen,
E-coli.
1. Introduction
In arid and semiarid regions such as the south-eastern Spain, on-farm Agricultural Water
Reservoirs (AWRs) which are used by many farmers and water agencies to manage irregular
water allocation for irrigation (Martínez-Alvarez et al., 2008), are characterized by a large
area to volume ratio, which implies substantial loss through evaporation, often representing a
significant fraction of the total water managed during the irrigation season, especially in
areas with a high evaporative demand (Craig et al., 2007; Martínez-Alvarez et al., 2008;
Martinez-Granados, 2011).
Besides, AWRs present a second substantial drawback; a high nutrient loading that induces
frequent algal blooms, resulting in serious water quality problems that can be of particular
concern for drip irrigation systems (Brainwood et al., 2004; Sperling et al., 2008).
The installation of Suspended Shade Cloth Covers (SSCCs) is one of the most promising
options since in addition to reduce evaporation (reduction factor = 75 to 90%; Craig et al.,
2005; Gallego-Elvira et al., 2011), it also improves water quality by (i) reducing algal
photosynthesis and primary production, (ii) excluding wind-borne dust and debris and (iii)
keeping or reducing the salinity of the stored water.
1