Author(s): Camila Cruz Grimaldo; Lia Ramos Fernandez; Jose Arapa Quispe

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Keywords: BDO; HEC-RAS; DO; Simulation; Streeter - Phelps

Abstract: The Lurín river originates from the melting of the snow-capped mountains of the Andes mountain range, crossing the districts of Cieneguilla, Pachacamac and Lurín; discharging its waters to the Pacific Ocean, supplying water to the inhabitants of the surrounding areas, it also maintains agricultural, livestock areas for human consumption with irrigation. In 20 km of the lower part of the river, 13 sampling points were distributed (8 in the river and 4 in effluents), obtaining the dissolved oxygen and the biochemical oxygen demand, the hydrodynamic characteristics such as: speed, depth and width of the river, the water balance considering the demands of the catchments of irrigators, the contribution of the Tinajas stream, the contribution of springs and seepage from the riverbed, during the period from February to August 2019. The digital elevation model was obtained, from images obtained from an unmanned aerial vehicle-UAV, the topography and satellite images of the study area, which allowed the simulation of the hydrodynamic characteristics of the river with the HEC-RAS program, and the formulas of Leopold and Maddock. The Streeter-Phelps water quality model was calibrated with the help of the excel solver optimization algorithm, obtaining the calibration of the parameters θk1, θk2, a, b, c, k1, k2 and k3 with values of (X ± S) : 1.19 ± 0.23, 1.02 ± 0.18, 0.87 ± 0.25, 0.85 ± 0.28, 2.53 ± 1.58 0.33 ± 0.89, 12, 66 ± 0.85 and 0.44 ± 2.43 respectively, in addition to a performance from “good” to “very good” for the Nash and RSR indices with a Pearson R of 0.9, significant for a student's T-test. with an α of 5%. During the dry season, the presence of diffuse contamination in the Pachacamac districts and seepage due to recharge from the aquifer to the river was evidenced. Three scenarios were simulated: optimization of the San Bartolo WWTP (i), passage of the irrigation canal from open to closed (ii), and the implementation of the Pachacamac WWTP (iii), being the optimization of the San Bartolo WWTP and the implementation of a Pachacamac WWTP, the most viable alternative for the river to meet the water quality standards, as well as the threshold flow.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221482

Year: 2022