Physical, chemical and microbiological effects of suspended shade cloth covers on stored water for irrigation

Abstract: The present study aims 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 the irrigated coastal plane of the Segura River Basin (south-eastern Spain) were monitored for 1 year. Two of them were covered with a black polyethylene SSCC, whereas the two others remained uncovered during the trial. The main physical, chemical and microbiological water quality parameters were monthly monitored with a multi-parametric instrument OTT-DS5 and water samples analysis. Additionally, a laboratory experiment replicating covered and uncovered AWR conditions was carried out to analyze the influence of water temperature and light intensity on the evolution of bacteria populations. The low transmitted solar radiation of the SSCC dramatically reduced the photosynthesis activity, limiting the algal bloom in covered AWRs. Despite this photosynthesis restriction and the lack of turbulence, the oxygen levels remained close to saturation in the covered AWRs as a result of the frequent water inflows. The installation of the cover also led to a reduction of 82% in Escherichia coli and faecal coliforms, partly due to the reduction of organic matter (mainly algae) and partly because of the lower water temperature. Data from the laboratory experiment confirmed the field results. Overall, the results show the implementation of SSCCs in AWRs produces significant effects in the stored water quality, which are mainly beneficial for irrigation purposes, especially in drip irrigation systems and when reclaimed water is reused. [Copyright &y& Elsevier]