Hydrogeochemical characterization and suitability of water for irrigation in new and old reservoirs in northern Espirito Santo, Brazil.

During the water crisis of 2015–2016, the construction of small earth-filled dams grew to supply irrigated crops of the north of Espírito Santo-ES, Brazil. This paper reports the hydrogeochemical study of eight reservoirs conducted between 10/2016 to 11/2017 to assess the water suitability for agricultural purposes and its risk to irrigation systems. The reservoirs of São Mateus (SM) are located in large drainage basins with many impoundments upstream. Nova Venecia's reservoirs (NV) have small and circular drainage areas with few, or any, upstream dams. The results are consistent with freshwater classification and Na-Cl composition to all reservoirs. Nevertheless, canonical discriminant analysis and Spearman's coefficients revealed distinct composition and patterns of correlations between municipalities. The mean permeability index of 53 and the low risk of sodicity and salinization (C1S1) demonstrate that these waters' use is harmless to the soil and crops. However, the phosphate contents make the new reservoirs susceptible to algae blooms. The same reservoirs also presented total solids and Fe levels above the tolerable limit for safety irrigation use, imposing a severe risk of clogging. The low replenishment of SM's reservoirs reflects the dispute over water resulting from the high number of impoundments in these drainage areas. The drought that preceded the study diminished the drainage basins' vegetation cover, favoring soil particles' runoff, elevating the TS and Fe levels, especially in the recently built reservoirs. Farmers must control soil erosion to avoid water quality compromise, to reduce the risk of failure and the irrigation system's maintenance cost. [ABSTRACT FROM AUTHOR]