Critical analysis of method used to establish environmental flows in the Segura river basin

Abstract

Minimum environmental flows can be calculated by different methodologies. The main methods habitually used in Spain can be grouped under the headings of Hydrological or Habitat Simulation methodologies. As part of the planning process established by the WFD, the Subdirectorate General for Water Planning and Sustainable Use of the Spanish Environment Ministry has developed a standard that sets out the specific way in which these methodologies must be used to determine minimum environmental flows. In the present work, minimum environmental flow values have been determined using different criteria on nine reaches in the Segura river basin (Spain), on the main course and in several tributaries. Calculations have been made by the most habitual methods and considering the official flow estimation criteria defined in the Segura Basin Management Plan and Spanish Environment Ministry recommendations, including those set out in the new Hydrologic Planning Regulation (RPH). The results obtained have then been analysed and compared. The values obtained using the official methodologies and instructions have been evaluated taking into account the criterion of the water lamina created on each reach and considering whether this is adequate for fish movement.