Reintroduction of shrimps in the lifeless Rímac river-Urban reach

Avila Miranda F.L.; Silva Dávila M.R. · Proceedings of the IAHR World Congress (2023) · DOI: 10.3850/978-90-833476-1-5_iahr40wc-p0644-cd

Resumen

The river shrimp, Cryphiops caementarius, is a crustacean that lives among the rocks at the bottom of the torrent rivers from the western coast of Peru to northern Chile. There are historical references about the existence of this specie in the urban reach of the Rímac River, the main source of water for Lima. However, at present all the fauna has disappeared due to the invasion of the fluvial territory and the detriment of its environmental quality. The objective of this research is to determine if the hydraulic conditions in the urban reach of the Rímac River, from the Army Bridge to the Bella Union Bridge, could allow the reintroduction and development of this species. For this purpose, it has been revised both literature about the morphological and hydraulic characteristics of the places where this crustacean has been found and the information collected during the inspection visits to the Rímac and Cañete rivers, before the Covid-19 pandemic. Four problems have been observed in the Rímac river-Urban reach: contamination, a discontinuity on the Army bridge (due to an 18 m drop), a decrease in natural discharges as well as the high turbidity of the water in the wet season. In 1978, the river shrimp was found in the “Cascadas de Barranco”, a cliff located in Lima along the Pacific Ocean, so this shows that the short reach and longitudinal discontinuity were not obstacles to the development of Cryphiops caementarius. There is a Master Plan for the Rímac River restoration project, which includes cleaning actions, water purification, and compliance with minimum flows (ANA, 2015). With the assumption that in the future the minimum environmental flow and an adequate water regime will be ensured, as well as the quality of the water and the substrate, hydraulic modeling was carried out to determine if it is possible to reintroduce river shrimp in the urban section of the Rímac river, considering the hydraulic conditions of its required habitat, mainly referring to water depth and average velocity values. The analyzes show that the morphological change produced in the studied reach has caused a decrease in the width of the bed in numerous cross-sections, causing values of water depths and average speeds that do not allow shrimp survival.

Instituciones: Universidad Nacional de Ingeniería