Microbiological Monitoring of Superficial Water of Lis Valley Irrigation District. Impacts of Agricultural Activities

Society’s demand for the preservation of water resources has led to major technological advances in irrigation management, simultaneously promoting socio-economic development and natural resources conservation. This study aims to assess the impact of agricultural activities at the Lis Valley Irrigation District (LVID) on the quality of superficial water. This information will support the improvement and the minimization of risks regarding the conservation of groundwater and surface water bodies in the valley. The physicochemical and microbiological quality of water samples collected at the inlets and outlet of the LVID was determined according to the analytical reference methods. Results showed that the water at the inlets of the LVID contains microbiological contamination, due to external sources. In general, the concentrations of total coliforms (TC) in the inlet water were 1.4 times lower than in the outflow water; however, an inverse situation was found with faecal coliforms (FC), faecal enterococci (FE), and ampicillin-resistant (Amp^r) Enterobacteriaceae. These data reveal that the LVID’s agricultural activities have not aggravated (and have even improved) those microbiological indicators of the outlet water when compared to those of the water which reaches the entrance of the district, available for agriculture. Concluding, the monitoring in a continuum of a few years will allow the assessment of risk situations of microbiological contamination to support the improvement of regional planning and agricultural management, being recommended to increase the sampling representativeness.