Minimum Flow Requirements of River Marabasco Aquatic Ecosystems, based on the Hydrological analysis and Biological Indicators

Abstract

The growing water shortage for covering subsistence and endowment requirements for population supply gets more complicated, making necessary the creation of a hydraulic infrastructure capable to warrant water supply for its diverse uses. However, this infrastructure most allows ecological integrity, which in turn depends on the variation of the flux regime upon which they are completely adapted. Marabasco river, is the natural border between Jalisco and Colima states, in which the construction of a dam is planed, being the reason for this work in which an analysis of the representative macroinvertebrate populations present at the influence region, taking in consideration the natural dynamic of the hydrological system in the river, in order to establish minimum flow needs for the maintenance of this community based on its needs. The abundance, tolerance and ecological requirements were determined for the benthonic macroinvertebrate community living at the river. Hydrological analysis was done with daily records along 37 years (1960-1990 and 1966-2002). Determined organisms families are clean water indicators, since they are dependent on the continuous flow of well-oxygenated unpolluted water. The hydrological analysis indicated that the dam would not retain more than 20% of the annual flow, although mean water flows are expected to be less over the dry season, between April and June. With an adequate dam operation politic, standard historical monthly registry behavior will be kept in order to satisfy fresh water demand for consumption and irrigation. There for, more than 80% of the dam’s water volume is expected to flow downstream, allowing for the maintenance of flux and depth conditions necessary for the permanence of the macroinvertebrate community at the river, and its arrival to the cost line.